2022/05/27 更新

写真a

アマノ ヒロシ
天野 浩
AMANO, Hiroshi
所属
未来材料・システム研究所 附属未来エレクトロニクス集積研究センター 未来デバイス部 教授
大学院担当
大学院工学研究科
学部担当
工学部
職名
教授
連絡先
メールアドレス

学位 1

  1. 工学博士 ( 1989年1月   名古屋大学 ) 

研究キーワード 10

  1. 発光ダイオード, レーザダイオード, トランジスタ, 太陽電池, 化合物半導体結晶成長, 半導体デバイス物理, ナノ構造

  2. 発光ダイオード

  3. 太陽電池

  4. 半導体デバイス物理

  5. 化合物半導体結晶成長

  6. レーザダイオード

  7. ナノ構造

  8. トランジスタ

  9. パワーデバイス 

  10. ミリ波 マイクロ波デバイス

研究分野 1

  1. その他 / その他  / 電子・電気材料工学

現在の研究課題とSDGs 2

  1. Ⅲ族窒化物半導体の結晶成長とデバイス応用

  2. 安心・安全で省エネルギー化に貢献する半導体デバイス

経歴 15

  1. 名古屋大学未来材料・システム研究所   未来エレクトロニクス集積研究センター   未来エレクトロニクス集積研究センターセンター長

    2015年10月 - 現在

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    国名:日本国

  2. 名古屋大学   未来材料・システム研究所 附属未来エレクトロニクス集積研究センター 未来デバイス部   教授

    2015年10月 - 現在

  3. 名城大学特別栄誉教授

    2015年7月 - 現在

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    国名:日本国

  4. 名城大学

    2015年7月 - 現在

  5. 名古屋市立大学 客員教授

    2015年4月 - 2016年3月

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    国名:日本国

  6. 名古屋大学特別教授

    2015年3月 - 現在

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    国名:日本国

  7. 名古屋大学   教授

    2015年3月 - 現在

  8. 中国清華大学   名誉教授

    2014年11月 - 現在

  9. 名古屋大学   大学院工学研究科 共通/大学院工学研究科)   赤﨑記念研究センター センター長

    2011年4月 - 現在

  10. 名古屋大学   大学院工学研究科 共通/大学院工学研究科)   赤﨑記念研究センター センター長

    2011年4月 - 現在

  11. 名古屋大学   工学研究科電子情報システム専攻   教授

    2010年4月 - 2015年10月

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    国名:日本国

  12. 名城大学理工学部教授

    2002年4月 - 2010年3月

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    国名:日本国

  13. 名城大学理工学部助教授

    1998年4月 - 2002年3月

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    国名:日本国

  14. 名城大学理工学部講師

    1992年4月 - 1998年3月

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    国名:日本国

  15. 名古屋大学助手(工学部)

    1988年4月 - 1992年3月

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    国名:日本国

▼全件表示

学歴 3

  1. 名古屋大学   工学研究科   電気工学・電気工学第二及び電子工学専攻

    1985年4月 - 1988年3月

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    国名: 日本国

  2. 名古屋大学   工学研究科   電気工学・電気工学第二及び電子工学専攻

    1983年4月 - 1985年3月

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    国名: 日本国

  3. 名古屋大学   工学部   電子工学科

    1979年4月 - 1983年3月

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    国名: 日本国

所属学協会 28

  1. 照明学会   名誉会員

    2016年9月 - 現在

  2. American Physical Society   フェロー

    2015年9月 - 現在

  3. 日本工学アカデミー   会員

    2015年6月 - 現在

  4. 日本化学会   名誉会員

    2015年6月 - 現在

  5. NAE(United States National Academy of Engineering)

    2015年6月 - 現在

  6. 電気学会   名誉員

    2015年5月 - 現在

  7. 日本表面科学会   特別栄誉会員

    2015年5月 - 現在

  8. 日本物理学会   名誉会員

    2015年4月 - 現在

  9. 電子情報通信学会    名誉員

    2015年3月 - 現在

  10. Material Research Society   Regular Member

    2010年1月 - 現在

  11. Optical Society of America

  12. SPIE

  13. 応用物理学会   Fellow、名誉会員

  14. Institute of Physics   Fellow

  15. 電気学会

  16. 電子情報通信学会

  17. 照明学会

  18. 日本表面科学会

  19. 日本物理学会

  20. 日本工学アカデミー

  21. 日本化学会

  22. 応用物理学会

  23. SPIE

  24. Optical Society of America

  25. NAE(United States National Academy of Engineering)

  26. Material Research Society

  27. Institute of Physics

  28. American Physical Society

▼全件表示

委員歴 30

  1. IWUMD-2017   組織委員長  

    2016年10月 - 2017年12月   

  2. 国立研究会開発法人産業術総合研究所   柱冠フェロー  

    2016年8月 - 現在   

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    団体区分:政府

  3. International Solid State Lighting Alliance   国際諮問委員  

    2016年8月 - 現在   

      詳細を見る

    団体区分:学協会

  4. OPIC2017   組織委員  

    2016年8月 - 現在   

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    団体区分:学協会

  5. 国際物理オリンピック日本大会   組織委員会副委員長  

    2016年5月 - 現在   

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    団体区分:その他

  6. 日本結晶成長学会   評議員  

    2016年4月 - 2019年3月   

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    団体区分:学協会

  7. 33rd International Conference on the Physics of Semiconductors国際諮問委員会   委員長  

    2015年9月 - 2016年8月   

  8. ・結晶成長の科学と技術第161委員会   委員  

    2015年8月 - 2016年3月   

  9. 2015 Rusnanoprize Award Committee   Member  

    2015年7月 - 現在   

  10. 2015 Rusnanoprize Award Committee   Member  

    2015年7月 - 現在   

  11. 2015 Rusnanoprize Award Committee   Member  

    2015年7月 - 現在   

  12. Optics & Photonics International Congress 2016組織委員会   委員  

    2015年7月 - 2016年6月   

  13. 江崎玲於奈賞委員会   委員  

    2015年6月 - 現在   

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    団体区分:その他

  14. 日本フォトニクス協議会 JPC関西   特別顧問  

    2015年5月 - 現在   

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    団体区分:その他

  15. 大阪大学光科学センター   特別顧問  

    2015年5月 - 2017年9月   

  16. ISPlasma2016/IC-PLANT2016組織委員会   委員長  

    2015年5月 - 2016年4月   

  17. 組織委員会委員     

    2014年7月 - 2015年3月   

  18. ISCS2014   Regional program chair  

    2013年4月 - 現在   

  19. Program Committee Chair  

    2013年4月 - 2014年3月   

  20. OPIC2013   組織委員  

    2012年7月 - 現在   

  21. OPIC2013   組織委員  

    2012年7月 - 現在   

  22. レーザ学会   専門委員会  

    2012年5月 - 2015年3月   

  23. 産業用LED応用研究会   委員長  

    2012年4月 - 現在   

  24. プログラム委員会副委員長  

    2012年2月 - 2012年4月   

  25. 4th International Symposium on Growth of III-Nitrides   Program Committee Chair  

    2011年7月 - 2012年7月   

  26. ICMOVPE-XVI   International Advisory COmmittee  

    2011年6月 - 2012年5月   

  27. 実行委員長  

    2011年4月 - 2012年10月   

  28. 名古屋市科学館企画調査委員会   企画調査委員  

    2010年8月 - 現在   

  29. 電子部品・材料研究専門委員会   専門委員  

    2010年5月 - 2012年5月   

  30. ワイドギャップ半導体光・電子デバイス第162委員会   特別顧問  

    2010年4月 - 2017年3月   

▼全件表示

受賞 37

  1. リンショッピング大学名誉博士号

    2017年5月  

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    受賞国:スウェーデン王国

  2. バジェ大学名誉博士号

    2017年1月   バジェ大学   青色LEDの開発

    天野 浩

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    受賞国:グアテマラ共和国

  3. オーベルニュ大学、ブレーズ・パスカル大学名誉博士号

    2016年5月   オーベルニュ大学、ブレーズ・パスカル大学  

    天野 浩

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    受賞国:フランス共和国

  4. パドバ大学名誉博士号

    2016年4月   パドバ大学  

    天野 浩

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    受賞国:イタリア共和国

  5. モンゴル国立大学名誉博士号

    2016年3月   モンゴル国立大学  

    天野 浩

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    受賞国:モンゴル国

  6. 応用物理学会化合物半導体エレクトロニクス業績賞(赤﨑勇賞)

    2016年3月   応用物理学会   青色及び紫外光デバイスの開発

    天野 浩

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    受賞区分:国内学会・会議・シンポジウム等の賞  受賞国:日本国

  7. 丸八会顕彰

    2015年10月   丸八会  

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    受賞国:日本国

  8. 第10回業績賞及び赤﨑勇賞

    2015年10月   日本結晶成長学会   高品質窒化物半導体の創出と青色・紫外光素子の実現

    天野 浩

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    受賞区分:国内学会・会議・シンポジウム等の賞  受賞国:日本国

  9. 2015 Asia Game Changers

    2015年10月   Asia Society  

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    受賞区分:国内外の国際的学術賞  受賞国:アメリカ合衆国

  10. 愛知県名誉県民

    2015年9月   愛知県  

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    受賞国:日本国

  11. 産学官連携功労者表彰 日本学術会議会長賞,

    2015年8月   日本学術会議会長   「短波長紫外LED」の開発

    天野 浩

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    受賞国:日本国

  12. 浜松市名誉市民

    2015年7月   浜松市  

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    受賞国:日本国

  13. 中日文化賞

    2015年5月   中日新聞  

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    受賞国:日本国

  14. 科学技術分野の文部科学大臣表彰 科学技術賞研究部門

    2015年4月   文部科学大臣   

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    受賞国:日本国

  15. 日本スウェーデン協会 名誉会員

    2015年3月   日本スウェーデン協会  

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    受賞国:日本国

  16. 電子情報通信学会 特別功績賞

    2015年3月   電子情報通信学会  

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    受賞国:日本国

  17. 名古屋市学術表彰

    2015年1月   名古屋市  

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    受賞国:日本国

  18. 愛知県学術顕彰

    2015年1月   愛知県  

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    受賞国:日本国

  19. 静岡県民栄誉賞

    2015年1月   静岡県  

     詳細を見る

    受賞国:日本国

  20. ノーベル物理学賞

    2014年12月   ノーベル財団  

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    受賞国:スウェーデン王国

  21. 文化功労者顕彰

    2014年11月   文部科学大臣  

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    受賞国:日本国

  22. 文化勲章

    2014年11月   首相  

     詳細を見る

    受賞国:日本国

  23. APEX/JJAP編集貢献賞

    2014年3月   応用物理学会  

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    受賞国:日本国

  24. IOP Fellow

    2011年10月   Institute of Physics  

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    受賞国:グレートブリテン・北アイルランド連合王国(英国)

  25. 英国物理学会 フェロー

    2011年10月  

    天野 浩

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    受賞国:グレートブリテン・北アイルランド連合王国(英国)

  26. ナイスステップな研究者2009

    2009年12月   文部科学省 科学技術政策研究所  

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    受賞国:日本国

  27. ナイスステップな研究者2009

    2009年12月   科学技術・政策研究所   青色及び紫外光デバイスの開発

    天野 浩

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    受賞国:日本国

  28. 応用物理学会フェロー

    2009年9月   応用物理学会  

     詳細を見る

    受賞国:日本国

  29. 日本結晶成長学会論文賞

    2008年11月   日本結晶成長学会  

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    受賞国:日本国

  30. 第1回 P&I パテント・オブ・ザ・イヤー

    2004年11月   東京工業大学精密工学研究所  

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    受賞国:日本国

  31. SSDM論文賞

    2003年9月   SSDM  

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    受賞国:日本国

  32. 武田賞

    2002年11月   竹田財団  

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    受賞国:日本国

  33. 丸文学術賞

    2001年3月   丸文財団  

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    受賞国:日本国

  34. 英国Rank賞

    1998年12月   Rank Foundation  

  35. 応用物理学会賞C(会誌賞)

    1998年9月   応用物理学会  

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    受賞国:日本国

  36. 米国IEEE/LEOS エンジニアリングアチーブメント賞

    1996年11月  

  37. オプトエレクトロニクス会議特別賞

    1994年7月  

▼全件表示

 

論文 757

  1. Improved performance of deep ultraviolet AlGaN-based light-emitting diode by reducing contact resistance of Al-based reflector

    Sim K.B., Jin J.Y., Kim S.K., Ko Y.J., Hwang G.W., Seong T.Y., Amano H.

    Journal of Alloys and Compounds   910 巻   2022年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Alloys and Compounds  

    In this study, chlorine (Cl) treatment was carried out on p-AlGaN to enhance the performance of ultraviolet-C light emitting diodes (UVC LEDs) by modifying ITO work function and hence reducing the contact resistance of ITO/Al reflector. The Cl-treated UVC LEDs exhibit the forward voltage of 6.88 V at 20 mA, whereas the reference samples show 7.50 V. The light output power and relative wall plug efficiency (WPE) of the Cl-treated UVC LEDs are enhanced by 17.1% at 500 mW and 19.5% at 100 mA, respectively, as compared to the reference. Additionally, the Cl-treated LEDs also display reduction in both the leakage current and ideality factor. Further, the photoluminescence (PL) intensity of AlGaN micro-disks is also enhanced by the Cl-treatment. X-ray photoemission spectroscopy (XPS) results indicate the formation of Cl-ITO at the ITO/p-AlGaN interface and the passivation of the surface states of AlGaN by Cl radicals. Based on the XPS results, a possible mechanism for the improved performance of Cl-treated UVC AlGaN-based LEDs is described and discussed.

    DOI: 10.1016/j.jallcom.2022.164895

    Scopus

  2. Dual-peak electroluminescence spectra generated from Al (n) /12Ga1-n/12N (n=2, 3, 4) for AlGaN-based LEDs with nonflat quantum wells

    Nagasawa Yosuke, Kojima Kazunobu, Hirano Akira, Ippommatsu Masamichi, Honda Yoshio, Amano Hiroshi, Chichibu Shigefusa F.

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   55 巻 ( 25 )   2022年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    The metastability of Al n/12Ga1-n/12N (n = 2, 3, and 4) was investigated by the statistical analysis of electroluminescence (EL) spectra having dual peaks with a peak-to-peak distance (pp) of >10 nm generated from nonflat Al x Ga1-x N (x ∼0.2) quantum wells (QWs) fabricated on c(0001) sapphire substrates with a miscut of 1.0° towards the m[1 1ˉ 00] axis. To explain the origins of the dual-peak EL (DPEL) spectra, which are often observed for AlGaN-QWs with Ga content of greater than 0.7, a nonflat QW model incorporating two metastable compositions, Al(n-1)/12Ga1-(n-1)/12N and Al n/12Ga1-n/12N (n: integer), is proposed. By the statistical analysis of peak wavelengths in DPEL spectra and the verification of EL spectral shapes, two series of featured EL peak wavelengths with intervals of 2-3 nm were obtained from five out of six LED wafers. The two series of featured EL peak wavelengths were assigned by comparison with the calculated EL wavelengths. Then, Al2/12Ga10/12N and Al3/12Ga9/12N were determined to be the origins of peaks with the longer and shorter wavelengths in the DPEL, respectively, in addition to the metastable Al n/12Ga1-n/12N (n= 4-9) compositions observed in our previous studies. When DPEL (pp> 10 nm) appeared, the difference in QW thickness between Al2/12Ga10/12N and Al3/12Ga9/12N tended to be larger than one monolayer (ML), indicating a significant amount of Ga or GaN mass transport. Furthermore, the Al2/12Ga10/12N and Al3/12Ga9/12N QWs are considered to have thicknesses of m ML (m: consecutive integers), suggesting the 1 ML configuration of Al and Ga atoms on the c(0001) plane. In addition, the DPEL obtained from nonflat Al x Ga1-x N (x ∼0.25) QWs by another research group was shown to be related to two metastable Al n/12Ga1-n/12N (n = 3, 4), similarly to our one exceptional LED wafer, which also agreed with the model proposed in this work.

    DOI: 10.1088/1361-6463/ac5d03

    Web of Science

    Scopus

  3. Author Correction: Laser slice thinning of GaN-on-GaN high electron mobility transistors.

    Tanaka A, Sugiura R, Kawaguchi D, Wani Y, Watanabe H, Sena H, Ando Y, Honda Y, Igasaki Y, Wakejima A, Ando Y, Amano H

    Scientific reports   12 巻 ( 1 ) 頁: 8175   2022年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41598-022-12628-0

    PubMed

  4. Laser slice thinning of GaN-on-GaN high electron mobility transistors

    Tanaka Atsushi, Sugiura Ryuji, Kawaguchi Daisuke, Wani Yotaro, Watanabe Hirotaka, Sena Hadi, Ando Yuto, Honda Yoshio, Igasaki Yasunori, Wakejima Akio, Ando Yuji, Amano Hiroshi

    SCIENTIFIC REPORTS   12 巻 ( 1 ) 頁: 7363   2022年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    As a newly developed technique to slice GaN substrates, which are currently very expensive, with less loss, we previously reported a laser slicing technique in this journal. In the previous report, from the perspective of GaN substrate processing, we could only show that the GaN substrate could be sliced by a laser and that the sliced GaN substrate could be reused. In this study, we newly investigated the applicability of this method as a device fabrication process. We demonstrated the thinning of GaN-on-GaN high-electron-mobility transistors (HEMTs) using a laser slicing technique. Even when the HEMTs were thinned by laser slicing to a thickness of 50 mm after completing the fabrication process, no significant fracture was observed in these devices, and no adverse effects of laser-induced damage were observed on electrical characteristics. This means that the laser slicing process can be applied even after device fabrication. It can also be used as a completely new semiconductor process for fabricating thin devices with thicknesses on the order of 10 mm, while significantly reducing the consumption of GaN substrates.

    DOI: 10.1038/s41598-022-10610-4

    Web of Science

    Scopus

    PubMed

  5. Interplay of sidewall damage and light extraction efficiency of micro-LEDs

    Park Jeong-Hwan, Pristovsek Markus, Cai Wentao, Cheong Heajeong, Kumabe Takeru, Lee Dong-Seon, Seong Tae-Yeon, Amano Hiroshi

    OPTICS LETTERS   47 巻 ( 9 ) 頁: 2250 - 2253   2022年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Optics Letters  

    This Letter describes the impact of shape on micro light-emitting diodes (µLEDs), analyzing 400 µm2 area µLEDs with various mesa shapes (circular, square, and stripes). Appropriate external quantum efficiency (EQE) can yield internal quantum efficiency (IQE) which decreases with increasing peripheral length of the mesas. However, light extraction efficiency (ηe) increased with increasing mesa periphery. We introduce analysis of Jpeak (the current at peak EQE) since it is proportional to the non-radiative recombination. Etching the sidewalls using tetramethylammonium hydroxide (TMAH) increased the peak EQE and decreased the sidewall dependency of Jpeak. Quantitatively, the TMAH etching reduced non-radiative surface recombination by a factor of four. Hence, shrinking µLEDs needs an understanding of the relationship between non-radiative recombination and ηe, where analyzing Jpeak can offer new insights.

    DOI: 10.1364/OL.456993

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    PubMed

  6. <p>The effect of dry etching condition on the performance of blue micro light-emitting diodes with reduced quantum confined Stark effect epitaxial layer</p>

    Park Jeong-Hwan, Cai Wentao, Cheong Heajeong, Ushida Yasuhisa, Lee Da-Hoon, Ando Yuto, Furusawa Yuta, Honda Yoshio, Lee Dong-Seon, Seong Tae-Yeon, Amano Hiroshi

    JOURNAL OF APPLIED PHYSICS   131 巻 ( 15 )   2022年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    As the size of micro light-emitting diodes (μLEDs) decreases, μLEDs encounter etching damage especially at the sidewalls that critically affects their properties. In this study, we investigated the influence of etching bias power (Pbias) on the performance of μLEDs and found that the current-voltage and light output-current characteristics of μLEDs were enhanced when Pbias was reduced. It was shown that at low Pbias, the chemical reaction between etching gas and gallium nitride, rather than ion sputtering, dominated the etching process, leading to low plasma damage and rough surface morphology. Additionally, to understand the etching-induced surface roughening behaviors, various substrates with different threading dislocation densities were treated at low Pbias. It was found that for the sample (with p-contact size of 10 × 10 μm2), the efficiency droop was approximately 20%, although the current reached 10 mA due most probably to the suppressed polarization effect in the quantum well. It was further observed that the external quantum efficiency (EQE) was dependent on Pbias, where the lowest Pbias yielded the highest maximum EQE, indicating that the plasma damage was mitigated by reducing Pbias. Optimization of dry etching and polarization-suppression conditions could pave the way for realizing high-performance and brightness μLEDs for next-generation displays.

    DOI: 10.1063/5.0085384

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  7. Continuous-wave lasing of AlGaN-based ultraviolet laser diode at 274.8 nm by current injection

    Zhang Ziyi, Kushimoto Maki, Yoshikawa Akira, Aoto Koji, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   15 巻 ( 4 )   2022年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We demonstrated continuous-wave lasing of an AlGaN-based ultraviolet laser diode, fabricated on a single-crystal AlN substrate when operating at 5 °C. The threshold current density and device series resistance were reduced by improvements to the epitaxial structure and electrode arrangement. A peak wavelength of 274.8 nm was observed for lasing at a drive current over 110 mA, which corresponded to a threshold current density of 3.7 kA cm-2. The operating voltage at the threshold current was as low as 9.6 V.

    DOI: 10.35848/1882-0786/ac6198

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  8. "Regrowth-free" fabrication of high-current-gain AlGaN/GaN heterojunction bipolar transistor with N-p-n configuration

    Kumabe Takeru, Watanabe Hirotaka, Ando Yuto, Tanaka Atsushi, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   15 巻 ( 4 )   2022年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    An AlGaN/GaN heterojunction bipolar transistor (HBT) with N-p-n configuration was fabricated by the "regrowth-free"method, resulting in a contamination-free emitter-base AlGaN/GaN heterojunction. The low-bias-power-based low-damage inductively coupled plasma-reactive ion etching was employed in this study for emitter mesa definition instead of the conventional selective-area-regrowth technique. The method successfully minimized the etching-induced damage in the p-GaN base layer and the contamination at the emitter-base AlGaN/GaN heterojunction. Consequently, the fabricated device exhibited a high current gain of 25, the highest current density of 15.0 kA cm-2, and the lowest on-state voltage offset of 0.75 V ever reported for AlGaN/GaN HBTs.

    DOI: 10.35848/1882-0786/ac6197

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  9. Mechanism and enhancement of anti-parasitic-reaction catalytic activity of tungsten-carbide-coated graphite components for the growth of bulk GaN crystals

    Nakamura Daisuke, Iida Kazuyoshi, Horibuchi Kayo, Aoki Yuko, Takahashi Naoko, Mori Yuto, Moriyama Miki, Nitta Shugo, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   15 巻 ( 4 )   2022年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    The working mechanism of the anti-parasitic-reaction (APR) catalyst of tungsten carbide (WC) coating on graphite in hydride vapor phase epitaxy GaN growth were examined. During NH3 annealing, the surface of WC is reduced as well as nitrided. The W2N topmost layer was found to work as an APR-active catalyst to suppress the formation of GaN polycrystals during high-rate HVPE-GaN growth, while the regions covered with thick pyrolytic graphite residues were catalytically inert. The formation of an additional W2C top layer on the WC underlayer was demonstrated to exhibit superior APR activity, i.e. complete suppression of GaN polycrystal formation.

    DOI: 10.35848/1882-0786/ac5ba4

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  10. Sputtered polycrystalline MgZnO/Al reflective electrodes for enhanced light emission in AlGaN-based homojunction tunnel junction DUV-LED

    Matsubara Taichi, Nagatat Kengo, Kushimoto Maki, Tomai Shigekazu, Katsumata Satoshi, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   15 巻 ( 4 )   2022年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    In this study, we enhanced the emission power of AlGaN-based tunnel junction deep-ultraviolet LEDs (TJ LEDs) by using a MgZnO and aluminum stacked structure as UV reflective electrodes on the anode side. The emission wavelength of the fabricated TJ LED was 284 nm, and the emission power was 57.3 mW at 63 A cm-2. The polycrystalline MgZnO enabled both conductivity and UV transmittance to be achieved, approximately doubling with a reflectance of the fabricated TJ LED at 284 nm compared to conventional TJ LED with Ti/Al. These factors contributed to the increased emission power of TJ LEDs.

    DOI: 10.35848/1882-0786/ac5acf

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  11. Structural design optimization of 279 nm wavelength AlGaN homojunction tunnel junction deep-UV light-emitting diode

    Nagata K., Anada S., Miwa H., Matsui S., Boyama S., Saito Y., Kushimoto M., Honda Y., Takeuchi T., Amano H.

    Applied Physics Express   15 巻 ( 4 )   2022年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We demonstrated the structural optimization of AlGaN tunnel junction (TJ) deep-ultraviolet light-emitting diodes by changing the thickness and impurity concentrations of p+-type and n+-type AlGaN constituting the TJ. By decreasing the total thickness of the TJ to 23 nm, the operating voltage reached a minimum of 8.8 V at 63 A cm-2. Further decrease in TJ thickness markedly increases the operating voltage. This finding implies that the depletion layer width becomes greater than the TJ thickness if it is smaller than 12 nm. Therefore, we conclude that the TJ thickness must be greater than the depletion layer width.

    DOI: 10.35848/1882-0786/ac60c7

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  12. Improved device performance of vertical GaN-on-GaN nanorod Schottky barrier diodes with wet-etching process

    Liao Y., Chen T., Wang J., Cai W., Ando Y., Yang X., Watanabe H., Tanaka A., Nitta S., Honda Y., Chen K.J., Amano H.

    Applied Physics Letters   120 巻 ( 12 )   2022年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    In this work, a deliberate etching-based top-down approach is proposed to fabricate the GaN nanorod (NR) Schottky barrier diode (SBD). As a key step during the fabrication, the impact of the wet-etching process on device performance is systematically studied. By virtue of the reduced surface states at the sidewall, the performance of NR SBD with the wet-etching process is substantially improved, delivering a forward turn-on voltage of 0.65 V, a current density of ∼10 kA/cm2 at 3 V, an ideality factor of 1.03, an ON/OFF current ratio of ∼1010, and no severe current collapse, along with a reverse breakdown voltage of 772 V.

    DOI: 10.1063/5.0083194

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  13. Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes

    Cha Jung-Suk, Lee Da-hoon, Sim Kee-Baek, Lee Tae-Ju, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   11 巻 ( 3 )   2022年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    For micro-light-emitting diode (LED)-based display applications, such as virtual reality and augmented reality, high-performance Ohmic contacts (namely, the improvement of current injection efficiency) is vital to the realization of high-efficiency micro-LEDs. The surface Fermi level pinning characteristics could be comprehended in terms of the relation between work function of metals (M) and Schottky barrier height (SBH, B). In this study, we have investigated the surface Fermi level pinning characteristics of (001) n-AlInP surfaces by employing Schottky diodes with different metals. With an increase in the temperature, B increases linearly and ideality factors (n) decreases. This behavior is related to the barrier height inhomogeneity. Inhomogeneity-modelbased B is evaluated to be in the range of 0.86 1.30 eV, which is dependent on the metal work functions and are similar to those measured from capacitance-voltage relation. Further, The S-parameter, the relation between B and M (d B/d M), is 0.36. This is indicative of the partial pinning of the surface Fermi level at the surface states placed at 0.95 eV below the conduction band. Furthermore, it is also shown that (NH4)2S-passivation results in an increases the mean SBH and the S-parameter (e.g., 0.52).

    DOI: 10.1149/2162-8777/ac5d66

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  14. Visualization of depletion layer in AlGaN homojunction p-n junction

    Nagata Kengo, Anada Satoshi, Saito Yoshiki, Kushimoto Maki, Honda Yoshio, Takeuchi Tetsuya, Yamamoto Kazuo, Hirayama Tsukasa, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   15 巻 ( 3 )   2022年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We analyzed the p-n junction of an aluminum gallium nitride (AlGaN) homojunction tunnel junction (TJ) deep-ultraviolet light-emitting diode by phase-shifting electron holography. We clearly obtained a phase image reflecting the band alinement of the p-n homojunction and derived a depletion layer width of approximately 10 nm. In addition, the observed depletion layer width for the AlGaN TJ was in good agreement with the simulated one reflecting the diffusion profile of Mg and Si, thus enabling a discussion on the electrical conduction mechanism for an AlGaN p-n junction.

    DOI: 10.35848/1882-0786/ac53e2

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  15. Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN

    Itoh Yuta, Watanabe Hirotaka, Ando Yuto, Kano Emi, Deki Manato, Nitta Shugo, Honda Yoshio, Tanaka Atsushi, Ikarashi Nobuyuki, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   15 巻 ( 2 )   2022年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100 °C with two beam currents. Photoluminescence spectra suggest that low-beam-current implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the density of intrinsic dislocation loops, suggesting decreases in the densities of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

    DOI: 10.35848/1882-0786/ac481b

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  16. Defect characterization of { 10 1 ¯ 3 } GaN by electron microscopy

    Kusch G., Frentrup M., Hu N., Amano H., Oliver R.A., Pristovsek M.

    Journal of Applied Physics   131 巻 ( 3 )   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    Advances in obtaining untwinned (10 1 ¯3)-oriented semi-polar GaN enable a new crystal orientation for the growth of green and red LED structures. We present a scanning electron microscopy study that combines the structural characterization of electron channeling contrast imaging with the optical characterization of cathodoluminescence hyperspectral imaging on a (10 1 ¯ 3) GaN layer. An extensive defect analysis revealed that the dominant defects consist of basal plane stacking faults (BSFs), prismatic stacking faults, partial dislocations, and threading dislocations. With a defect density of about an order of magnitude lower than in comparable. The optical properties of the defects have been characterized from 10 to 320 K, showing BSF luminescence at room temperature indicating a reduced density of non-radiative recombination centers in the as-grown samples compared to established semi- and non-polar orientations. Our findings suggest that growth along (10 1 ¯3) has the potential for higher radiative efficiency than established semi-polar orientations.

    DOI: 10.1063/5.0077084

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  17. Perspective on thermal conductance across heterogeneously integrated interfaces for wide and ultrawide bandgap electronics

    Cheng Zhe, Graham Samuel, Amano Hiroshi, Cahill David G.

    APPLIED PHYSICS LETTERS   120 巻 ( 3 )   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    Heterogeneous integration is important to create multi-functionality in future electronic devices. However, few thermal studies of the interfaces formed in these integrated devices have been reported before. Recently, integrated interfaces by surface-Activated bonding were found to have high thermal boundary conductance, which provides a solution for heat dissipation of GaN and β-Ga2O3-based power electronics. Here, we review the recent progress on the interfacial thermal transport across heterogeneously integrated interfaces, including transferred van der Waals force bonded interfaces, surface-Activated bonded interfaces, plasma bonded interfaces, and hydrophilic bonded interfaces. This Perspective specifically focuses on applications of thermal management strategies of electronics, especially power electronics. Finally, the challenges, such as high-Throughput thermal measurements of buried interfaces, thermal property-structure relations of interfaces bonded under different conditions, theoretical understanding of interfacial thermal transport, and device demonstrations, are pointed out.

    DOI: 10.1063/5.0077039

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  18. Threshold increase and lasing inhibition due to hexagonal-pyramid-shaped hillocks in AlGaN-based DUV laser diodes on single-crystal AlN substrate

    Kushimoto Maki, Zhang Ziyi, Honda Yoshio, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   61 巻 ( 1 )   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    The presence of hexagonal-pyramid-shaped hillocks (HPHs) in AlGaN epitaxial films affects device characteristics; this effect is significant in DUV laser diodes (LDs) on AlN substrates, where the presence of HPHs under the p-electrode increases the threshold current density and inhibits the lasing. In this study, we investigated the difference between the lasing characteristics of LDs with and without HPHs. It was found that in the presence of HPHs, the threshold excitation power density increased and the slope efficiency decreased by optical excitation. To investigate the cause of these phenomena, we performed structural, optical, and electrical analyses of the HPHs. Various imaging techniques were used to directly capture the characteristics of the HPHs. As a result, we concluded that HPHs cause the degradation of LD characteristics due to a combination of structural, optical, and electrical factors.

    DOI: 10.35848/1347-4065/ac3a1d

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  19. Ohmic Contact to p-Type GaN Enabled by Post-Growth Diffusion of Magnesium

    Wang Jia, Lu Shun, Cai Wentao, Kumabe Takeru, Ando Yuto, Liao Yaqiang, Honda Yoshio, Xie Ya-Hong, Amano Hiroshi

    IEEE ELECTRON DEVICE LETTERS   43 巻 ( 1 ) 頁: 150 - 153   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Electron Device Letters  

    We demonstrated the formation of excellent Ohmic contact to p-type GaN (including the plasma etching-damaged p-type GaN which otherwise exhibited undetectable current within ±5 V) by the post-growth diffusion of magnesium. The specific contact resistivity on the order of 10-4Omega cm2 (extracted at V=0 V) was achieved on the plasma-damaged p-GaN with linear current-voltage characteristics by the transfer length method (TLM) measurement. The improvement in current by a factor of over 109 was also obtained on the plasma-damaged p-n junction diode after the same Mg-treatment. These experimental results indicate a great potential of post-growth diffusion of Mg to overcome the bottleneck of forming a good Ohmic contact to p-GaN.

    DOI: 10.1109/LED.2021.3131057

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  20. Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg

    Lu Shun, Deki Manato, Wang Jia, Ohnishi Kazuki, Ando Yuto, Kumabe Takeru, Watanabe Hirotaka, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS LETTERS   119 巻 ( 24 )   2021年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    We have demonstrated a fabrication process for the Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg. An Ohmic contact with a contact resistance of 0.158 ω cm2 is realized on p-GaN ([Mg] = 1.3 × 1017 cm-3). The contact resistance of p-type GaN with higher Mg concentration ([Mg]=1.0 × 1019 cm-3) can also be reduced to 2.8 × 10-5 ω cm2. A localized contact layer is realized without any etching or regrowth damage. The mechanism underlying this reduced contact resistance is studied by scanning transmission electron microscopy with energy dispersive x-ray spectroscopy and secondary ion mass spectrometry, representing a mutual diffusion of Ga and Mg atoms on the interface. Reductions in the barrier height and surface depletion width with the nitrogen-annealed Mg layer are confirmed by XPS and Hall effect measurements qualitatively.

    DOI: 10.1063/5.0076764

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  21. Uniting a III-Nitride Transmitter, Waveguide, Modulator, and Receiver on a Single Chip

    Xie Mingyuan, Jiang Yan, Gao Xumin, Cai Wei, Yuan Jialei, Zhu Hongbo, Wang Yongjin, Zeng Xuefeng, Zhang Zhiyu, Liu Yuhuai, Amano Hiroshi

    ADVANCED ENGINEERING MATERIALS   23 巻 ( 12 )   2021年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Advanced Engineering Materials  

    The integration of III-nitride electronics and photonics is of great interest toward future computing systems with low power consumption. Multifunctioning multiple quantum well (MQW) diodes can address the challenging issue for on-chip integration of a light source, which is a key component to drive the photonic circuits. Herein, a transmitter, waveguide, modulator, and receiver are monolithically integrated on a III-nitride-on-silicon platform to perform light emission, transmission, modulation, and detection simultaneously. Both the receiver and modulator exhibit sufficient sensitivity to optical signals from the transmitter, which has an identical InGaN/AlGaN multiple quantum well (MQW) structure because the III-nitride diode provides spectral overlap between the emission and absorption spectra. On-chip data communication among these optical components is achieved using light, and the effective wavelength range is from 365 to 385 nm, in which multifunctional devices can be operated.

    DOI: 10.1002/adem.202100582

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  22. Discrete wavelengths observed in electroluminescence originating from Al<inf>1/2</inf>Ga<inf>1/2</inf>N and Al<inf>1/3</inf>Ga<inf>2/3</inf>N created in nonflat AlGaN quantum wells

    Nagasawa Y., Kojima K., Hirano A., Sako H., Hashimoto A., Sugie R., Ippommatsu M., Honda Y., Amano H., Chichibu S.F.

    Journal of Physics D: Applied Physics   54 巻 ( 48 )   2021年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    When nonflat Al x Ga1-x N quantum wells (QWs) for producing 285 nm light emitting diodes (LEDs) were fabricated on n-AlGaN on AlN templates with dense macrosteps on c(0001) sapphire substrates with a 1.0 miscut relative to the m[1-100] axis, composite electroluminescence (EL) spectra from both inclined and terrace zones in Al x Ga1-x N QWs (x∼ 1/3) were generated owing to compositional and thickness modulations. The shoulder or main peaks in composite EL spectra tended to locate at fixed discrete wavelengths of ∼287, ∼292, and ∼296 nm from 12 nonuniform 285 nm LED wafers that were involved in nonnegligible run-to-run drift, even though these wafers were fabricated using the same source gas flow parameters for metal-organic vapor phase epitaxy. The discrete wavelengths of ∼287, ∼292, and ∼296 nm were attributed to EL from Al1/3Ga2/3N QWs with thicknesses of 8, 9, and 10 monolayers (ML), respectively, by referring to the results of cathodoluminescence (CL) analysis. Also, when nonflat Al x Ga1-x N QWs (x∼ 1/2) for 265 nm LEDs were grown, single-peak-like EL spectra were mainly generated from the inclined zones in nonflat QWs. The EL spectra taken from four nonuniform 265 nm LED wafers tended to show weak structures or main peaks at ∼257, ∼261, ∼266, and ∼271 nm, which were also attributed to emissions from Al1/2Ga1/2N QWs with thicknesses of 5, 6, 7, and 8 ML, respectively, by referring to CL analysis results. The creation of Al1/3Ga2/3N and Al1/2Ga1/2N in nonflat QWs in this work was in agreement with the results of our previous studies that indicated the creation of metastable Al n/12Ga1-n/12N (n: consecutive natural numbers). Furthermore, QW thicknesses of consecutive n ML may imply that Al1/3Ga2/3N and Al1/2Ga1/2N have 1 ML configurations of Al and Ga atoms on a c(0001) plane.

    DOI: 10.1088/1361-6463/ac2065

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  23. Multiple electron beam generation from InGaN photocathode

    Sato Daiki, Shikano Haruka, Koizumi Atsushi, Nishitani Tomohiro, Honda Yoshio, Amano Hiroshi

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B   39 巻 ( 6 )   2021年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics  

    In this study, we generated 25 multielectron beam (MEB) using an InGaN photocathode with a negative electron affinity state irradiating with 25 multilaser beam. The uniformity of the MEB and the total electron beam current were evaluated. A laser beam was split into 25 laser beams using a spatial light modulator. The coefficient of variation (CV) of laser power was 20%. The CV of quantum efficiency was 1.1%. The CV of electron beam current was 12%, and the total current was about 1.2 μA. These results will enhance the development of the MEB-defect inspection using the InGaN photocathode.

    DOI: 10.1116/6.0001272

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  24. Modified Small Signal Circuit of AlGaN/GaN MOS-HEMTs Using Rational Functions

    Jadhav Aakash, Ozawa Takashi, Baratov Ali, Asubar Joel T., Kuzuhara Masaaki, Wakejima Akio, Yamashita Shunpei, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi, Roy Sourajeet, Sarkar Biplab

    IEEE TRANSACTIONS ON ELECTRON DEVICES   68 巻 ( 12 ) 頁: 6059 - 6064   2021年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Transactions on Electron Devices  

    Conventional lumped small signal circuit (SSC) models of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) are derived from the low frequency portion of the experimentally measured ${Y}$ -parameters. Consequently, these models cannot faithfully capture the high frequency behavior of the device. In this work, modified SSC models of AlGaN/GaN MOS-HEMTs are developed by fitting the entire broadband measured ${Y}$ -parameters of the device with rational functions. These rational functions are then physically realized using additional passive circuit elements added to the conventional SSC model. The accuracy of the proposed SSC models can be improved by increasing the order of the rational functions. The proposed models are demonstrably more accurate than the conventional SSC models in estimating the higher order poles and zeroes present in the experimentally measured ${Y}$ -parameters of AlGaN/GaN MOS-HEMTs.

    DOI: 10.1109/TED.2021.3119528

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  25. Vertical GaN p(+)-n junction diode with ideal avalanche capability grown by halide vapor phase epitaxy (vol 119, 152102, 2021)

    Ohnishi Kazuki, Kawasaki Seiya, Fujimoto Naoki, Nitta Shugo, Watanabe Hirotaka, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS LETTERS   119 巻 ( 20 )   2021年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    After the paper was published,1we found errors in the manuscript shown in page 152102-2. In the original published article, the SIMS detec-tion limits of [O] and [H] were written as 7 × 1015and 3 × 1015cm-3, respectively. The corrected detection limits of [O] and [H] are 6 × 1015and 3 × 1016cm-3, respectively. The SIMS depth profiles shown in Fig. 2(b) and the conclusions of the paper are not affected by this erratum.

    DOI: 10.1063/5.0077364

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  26. OBITUARY Isamu Akasaki

    Amano Hiroshi

    PHYSICS TODAY   74 巻 ( 11 ) 頁: 63 - 63   2021年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  27. Vertical GaN p(+)-n junction diode with ideal avalanche capability grown by halide vapor phase epitaxy

    Ohnishi Kazuki, Kawasaki Seiya, Fujimoto Naoki, Nitta Shugo, Watanabe Hirotaka, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS LETTERS   119 巻 ( 15 )   2021年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    A vertical GaN p+-n junction diode with an ideal breakdown voltage was grown by halide vapor phase epitaxy (HVPE). A steep p+-n interface was observed even with the use of the HVPE method. No Si-accumulating layer was formed at the p+-n interface because of the continuous HVPE growth from the n-type drift layer to the p-type layer. This method provides improved electrical properties compared with the regrowth of p-type GaN layers. The minimum ideality factor of approximately 1.6 was obtained. The breakdown voltage increased from 874 to 974 V with the increase in the temperature from 25 to 200 °C, which suggests that avalanche multiplication causes the breakdown. The temperature-dependent breakdown voltage was in good agreement with the breakdown voltage calculated using the ideal critical electric field. These results indicate that HVPE is promising for the fabrication of vertical GaN power devices.

    DOI: 10.1063/5.0066139

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  28. Effective neutron detection using vertical-type BGaN diodes

    Nakano Takayuki, Mochizuki Ken, Arikawa Takuya, Nakagawa Hisaya, Usami Shigeyoshi, Honda Yoshio, Amano Hiroshi, Vogt Adrian, Schuett Sebastian, Fiederle Michael, Kojima Kazunobu, Chichibu Shigefusa F., Inoue Yoku, Aoki Toru

    JOURNAL OF APPLIED PHYSICS   130 巻 ( 12 )   2021年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    In this study, vertical-type thick BGaN PIN diodes were successfully fabricated to improve the neutron capture rate of BGaN diodes by improving the BGaN epitaxial growth technique. In this technique, 5-μm-thick epitaxial growth was achieved using trimethylboron as a B metal-organic source, which suppressed the gas-phase reaction. The α-particle energy spectrum, the neutron pulse signal, and the residual energy of particles emitted from a neutron capture reaction were measured using the fabricated BGaN diodes by performing radiation detection measurements. The detected signal position in the neutron detection signal spectrum was similar to that of 2.3 MeV α-particles. These results indicate that vertical-type BGaN diodes can be used as effective neutron detectors.

    DOI: 10.1063/5.0051053

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  29. Smart-cut-like laser slicing of GaN substrate using its own nitrogen

    Tanaka Atsushi, Sugiura Ryuji, Kawaguchi Daisuke, Yui Toshiki, Wani Yotaro, Aratani Tomomi, Watanabe Hirotaka, Sena Hadi, Honda Yoshio, Igasaki Yasunori, Amano Hiroshi

    SCIENTIFIC REPORTS   11 巻 ( 1 ) 頁: 17949   2021年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    We have investigated the possibility of applying lasers to slice GaN substrates. Using a sub-nanosecond laser with a wavelength of 532 nm, we succeeded in slicing GaN substrates. In the laser slicing method used in this study, there was almost no kerf loss, and the thickness of the layer damaged by laser slicing was about 40 µm. We demonstrated that a standard high quality homoepitaxial layer can be grown on the sliced surface after removing the damaged layer by polishing.

    DOI: 10.1038/s41598-021-97159-w

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  30. Effects of Current, Temperature, and Chip Size on the Performance of AlGaInP-Based Red Micro-Light-Emitting Diodes with Different Contact Schemes

    Lee Da-Hoon, Lee Sang-Youl, Shim Jong-In, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   10 巻 ( 9 )   2021年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    We have investigated the performance of AlGaInP-based red micro-light-emitting diodes (micro-LEDs) with different n-type contact schemes as functions of current, ambient temperature, and chip size. The samples with AuGe/Ni/Au contact revealed wider full width at half maximum of electroluminescence than that with the Pd/Ge contact. All samples also exhibited broad peaks at wavelengths between ∼632 and ∼640 nm, whose intensity depended on the type of contact schemes and temperature. Regardless of the contact schemes, the 10 μm-size samples showed a larger temperature-dependent reduction in the output power at current density of <50 A cm-2 than the 100 μm-size ones. Above 100 A cm-2, however, both samples showed similar temperature dependence. Irrespective of the contact schemes, the main peak of the 100-μm samples was red-shifted, whereas no red-shift was detected in the 10-μm samples. The third peak of the AuGe-based contact samples became more dominant at 700 A cm-2 than the main peak, whereas that of the PdGe contact samples became more dominant at 1000 A cm-2. Based on the chip size, current, contact scheme, and temperature dependence, the performance degradation of the red micro-LEDs is described and discussed.

    DOI: 10.1149/2162-8777/ac2029

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  31. Quasi-ballistic thermal conduction in 6H-SiC

    Cheng Z., Lu W., Shi J., Tanaka D., Protik N. H., Wang S., Iwaya M., Takeuchi T., Kamiyama S., Akasaki I., Amano H., Graham S.

    MATERIALS TODAY PHYSICS   20 巻   2021年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Materials Today Physics  

    The minimization of electronics makes heat dissipation of related devices an increasing challenge. When the size of materials is smaller than the phonon mean free paths, phonons transport without internal scattering and laws of diffusive thermal conduction need to be revisited. This work reports the temperature dependent thermal conductivity of doped epitaxial 6H–SiC and monocrystalline porous 6H–SiC below room temperature probed by time-domain thermoreflectance. Strong quasi-ballistic thermal transport was observed in these samples, especially at low temperatures. Doping and structural boundaries were applied to tune the quasi-ballistic thermal transport since dopants selectively scatter high-frequency phonons while boundaries scatter phonons with long mean free paths. Exceptionally strong phonon scattering by boron dopants are observed, compared to nitrogen dopants. Furthermore, orders of magnitude reduction in the measured thermal conductivity was observed at low temperatures for the porous 6H–SiC compared to the epitaxial 6H–SiC. Finally, first principles calculations and a simple Callaway model are built to understand the measured thermal conductivities. Our work sheds light on the fundamental understanding of thermal conduction in technologically-important wide bandgap semiconductors such as 6H–SiC and will impact applications such as thermal management of 6H–SiC-related electronics and devices.

    DOI: 10.1016/j.mtphys.2021.100462

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  32. Gallium nitride wafer slicing by a sub-nanosecond laser: effect of pulse energy and laser shot spacing

    Sena Hadi, Tanaka Atsushi, Wani Yotaro, Aratani Tomomi, Yui Toshiki, Kawaguchi Daisuke, Sugiura Ryuji, Honda Yoshio, Igasaki Yasunori, Amano Hiroshi

    APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING   127 巻 ( 9 )   2021年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics A: Materials Science and Processing  

    Gallium nitride (GaN)-based devices surpass the traditional silicon-based power devices in terms of higher breakdown voltage, faster-switching speed, higher thermal conductivity, and lower on-resistance. However, heteroepitaxial GaN growths like GaN on sapphire are not suitable for power devices due to the threading dislocation densities as high as 108/cm2. Recently, homoepitaxial GaN growth has become possible thanks to the native GaN substrates with dislocation densities in the order of 104/cm2 but the extremely high cost of the GaN substrates makes the homoepitaxy method unacceptable for industrial applications, and the slicing of wafers for reusing them is an effective solution for cost reduction. In this study, we will investigate a route for slicing the GaN single crystal substrate by controlling the laser pulse energy and changing the distance between each laser shot. The 2D and 3D crack propagations are observed by a multiphoton confocal microscope, and the cross section of samples is observed by a scanning electron microscope (SEM). The results showed that two types of radial and lateral cracking occurred depending on the pulse energy and shot pitch, and controlling them was of importance for attaining a smooth GaN substrate slicing. Cross-sectional SEM images showed that at suitable pulse energy and distance, crack propagation could be controlled with respect to the irradiation plane.

    DOI: 10.1007/s00339-021-04808-y

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  33. High-Gain Gated Lateral Power Bipolar Junction Transistor

    Wang Jia, Xie Ya-Hong, Amano Hiroshi

    IEEE ELECTRON DEVICE LETTERS   42 巻 ( 9 ) 頁: 1370 - 1373   2021年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Electron Device Letters  

    We demonstrated a prototype Gated Lateral power bipolar junction transistor (GLP-BJT) on wide bandgap semiconductor. The device combined the intrinsic advantages of high current gain of a Gated Lateral-BJT and good current handling and voltage blocking capabilities of GaN material. As a result, the common-emitter current gain remained over 300 at a high collector current density of 2 kA/cm2 despite a wide p-base region of 2 &#x03BC;m. The open base breakdown voltage BVCEO was over 300 V corresponding to a high critical field of 2.5 MV/cm. These figures of merit show great promise of GaN-based GLP-BJT in power applications and also shed light on the development of state-of-the-art bipolar transistors based on other wide bandgap semiconductors.

    DOI: 10.1109/LED.2021.3099982

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  34. Stable electrical performance of AlGaInP-based red micro-light emitting diode by controlling interfacial morphologies of metal contacts

    Lee Da-Hoon, Seong Tae-Yeon, Amano Hiroshi

    JOURNAL OF ALLOYS AND COMPOUNDS   872 巻   頁: 159629   2021年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Alloys and Compounds  

    The stable electrical performance of micro-light-emitting diodes (micro-LEDs) is critical to display application. We investigated the effect of the interface morphologies of contacts to n-AlInP on the electrical stability of AlGaInP-based red micro-LEDs. Regardless of chip sizes (100 µm or 10 µm-size), micro-LEDs with Pd/Ge contacts gave lower and stable forward voltages than those with AuGe/Ni/Au contacts. When annealed at 450 °C, the AuGe/Ni/Au contact underwent seriously inhomogeneous interfacial reactions, resulting in a large variation of interfacial morphologies across the whole contact/AlInP interface. However, the Pd/Ge contact exhibited similar morphologies across the whole interface when annealed. Further, when operated at 800 A/cm2, micro-LEDs with the Pd/Ge contacts underwent less electrical degradation than the ones with the AuGe/Ni/Au contacts. Based on the electrical and scanning transmission electron microscope (STEM) results, the unstable electrical behavior of red micro-LEDs with the AuGe/Ni/Au contact is discussed.

    DOI: 10.1016/j.jallcom.2021.159629

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  35. Improving light output power of AlGaN-based deep-ultraviolet light-emitting diodes by optimizing the optical thickness of p-layers

    Matsukura Yusuke, Inazu Tetsuhiko, Pernot Cyril, Shibata Naoki, Kushimoto Maki, Deki Manato, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   14 巻 ( 8 )   2021年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    In this study, we investigated the relationship of light output power with the optical thickness of the p-layers in AlGaN-based deep ultraviolet light-emitting diodes with a transparent high-Al-composition p-AlGaN clad layer, a thin p-GaN contact layer, and a reflective p-type electrode. By adjusting the thickness of the transparent high-Al-composition p-AlGaN clad layer, we observed a marked change in light output power. A maximum light output power of 385 mW at 1500 mA, a maximum external quantum efficiency of 15.7% at 10 mA, and a maximum wall-plug efficiency of 15.3% at 10 mA were obtained at an emission wavelength of 275 nm.

    DOI: 10.35848/1882-0786/ac154c

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  36. Reduction in operating voltage of AlGaN homojunction tunnel junction deep-UV light-emitting diodes by controlling impurity concentrations

    Nagata K., Makino H., Miwa H., Matsui S., Boyama S., Saito Y., Kushimoto M., Honda Y., Takeuchi T., Amano H.

    Applied Physics Express   14 巻 ( 8 )   2021年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We reduced the operating voltage of AlGaN homojunction tunnel junction (TJ) deep-ultraviolet (UV) light-emitting diodes (LEDs) by two approaches: the suppression of carbon incorporation and the doping of a high concentration of silicon in an n+-AlGaN layer. The AlGaN homojunction TJ deep-UV LEDs had a significantly reduced forward voltage upon suppressing the incorporation of carbon in the n+-AlGaN layer. The suppression of electron compensation by carbon in nitrogen sites and the doping of a high concentration of silicon in an n+-AlGaN layer are important for reducing the operating voltage of AlGaN homojunction TJ deep-UV LEDs.

    DOI: 10.35848/1882-0786/ac0fb6

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  37. Impact of gate electrode formation process on Al<inf>2</inf>O<inf>3</inf>/GaN interface properties and channel mobility

    Ando Y., Deki M., Watanabe H., Taoka N., Tanaka A., Nitta S., Honda Y., Yamada H., Shimizu M., Nakamura T., Amano H.

    Applied Physics Express   14 巻 ( 8 )   2021年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    The interface properties of GaN metal-insulator-semiconductor (MIS) structures with a gate electrode metal deposited by electron beam (EB) or resistive heating evaporation were investigated. Also, the impact of the interface properties on the channel mobility in GaN MIS field-effect transistors was investigated. It was confirmed that interface charges including both interface states and positive fixed charges were introduced to an Al2O3/GaN interface by the formation of a gate electrode by EB evaporation. Consequently, the introduced interface charges degraded the electron mobility in the MIS channel.

    DOI: 10.35848/1882-0786/ac0ffa

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  38. Electrical properties and structural defects of p-type GaN layers grown by halide vapor phase epitaxy

    Ohnishi Kazuki, Amano Yuki, Fujimoto Naoki, Nitta Shugo, Watanabe Hirotaka, Honda Yoshio, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   566 巻   2021年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Crystal Growth  

    The electrical properties and structural defects of p-type GaN layers with Mg concentrations from 8.0 × 1018 to 8.3 × 1019 cm−3 grown by halide vapor phase epitaxy (HVPE) were investigated. In all samples, p-type conduction was confirmed at room temperature. The hole concentration at room temperature decreased in a heavily Mg-doped sample. By analyzing the results of Hall-effect measurements at various temperatures, the acceptor concentration decreased in a heavily Mg-doped sample, whereas the compensating donor concentration increased. These results affect the decrease in the hole concentration. The hole mobility decreased with increasing acceptor concentration. In the heavily Mg-doped sample, pyramidal inversion domains (PIDs) were formed. The size of each PID in an HVPE-grown sample is in good agreement with that Mg-doped GaN layers grown by metalorganic vapor phase epitaxy (MOVPE). Thus, the formation mechanism of PIDs in HVPE-grown samples is possibly the same as that in MOVPE-grown samples. Energy-dispersive X-ray spectroscopy shows that Mg atoms accumulate in PIDs, which suggests that Mg atoms in PIDs are electrically inactive, inhibiting the increase in the acceptor concentration. These results are useful guidelines for fabricating p-type GaN layers with higher hole concentrations by HVPE.

    DOI: 10.1016/j.jcrysgro.2021.126173

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  39. 赤﨑勇先生のご逝去を悼む

    天野 浩

    応用物理   90 巻 ( 7 ) 頁: 455 - 455   2021年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:公益社団法人 応用物理学会  

    DOI: 10.11470/oubutsu.90.7_455

    CiNii Research

  40. 赤﨑 勇先生を偲んで

    天野 浩

    日本物理学会誌   76 巻 ( 7 ) 頁: 478 - 478   2021年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 日本物理学会  

    <p>追悼</p><p>赤﨑 勇先生を偲んで</p>

    DOI: 10.11316/butsuri.76.7_478

    CiNii Research

  41. Vertical GaN-on-GaN nanowire Schottky barrier diodes by top-down fabrication approach

    Liao Y., Chen T., Wang J., Ando Y., Cai W., Yang X., Watanabe H., Hirotani J., Tanaka A., Nitta S., Honda Y., Chen K.J., Amano H.

    Japanese Journal of Applied Physics   60 巻 ( 7 )   2021年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    An optimized top-down approach was utilized to fabricate vertical GaN-on-GaN nanowire Schottky barrier diodes (NWSBDs) in this letter. The suppressed reverse leakage current and enhanced breakdown voltage (BV) of the vertical GaN NWSBDs are attributed to the reduced electric field at the interface of the Schottky junction achieved through the dielectric reduced surface field technique. As-fabricated NWSBD delivers a low turn-on voltage of 0.80 V, a near-unity ideality factor of 1.04, along with a soft BV of 480 V. The measured soft BV is comparable with the avalanche BV of the p-n diode with a similar net doping concentration in the drift region.

    DOI: 10.35848/1347-4065/ac06b5

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  42. Isamu Akasaki: The Pioneer of Blue LEDs and his Collaboration with pss OBITUARY

    Amano Hiroshi

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   218 巻 ( 14 )   2021年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssa.202100329

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  43. Non-polar true-lateral GaN power diodes on foreign substrates

    Wang Jia, Yu Guo, Zong Hua, Liao Yaqiang, Lu Weifang, Cai Wentao, Hu Xiaodong, Xie Ya-Hong, Amano Hiroshi

    APPLIED PHYSICS LETTERS   118 巻 ( 21 )   2021年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    We have demonstrated non-polar GaN power diodes (Schottky barrier diode and p-n junction diode) on foreign substrates featuring the true-lateral p-n and metal-semiconductor junctions. The diodes were fabricated on GaN islands laterally overgrown on the mask-patterned sapphire and Si substrates by metalorganic vapor phase epitaxy. The anode and cathode were formed on the opposed a-plane sidewalls of the island, making the device architecture essentially like the 90° rotation of the desired true-vertical power diodes. The ideality factor of the Schottky barrier diode remained 1.0 (from 1.00 to 1.05) over 7 decades in current. Specifically, a high critical electric field of 3.3 MV/cm was demonstrated on the p-n junction diode with avalanche capability. These performances reveal a strong potential of non-polar GaN with the true-lateral junctions for high power applications.

    DOI: 10.1063/5.0051552

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  44. The stability of graphene and boron nitride for III-nitride epitaxy and post-growth exfoliation.

    Park JH, Yang X, Lee JY, Park MD, Bae SY, Pristovsek M, Amano H, Lee DS

    Chemical science   12 巻 ( 22 ) 頁: 7713 - 7719   2021年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Chemical Science  

    A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material. However, when graphene, a representative 2-D material, is present on substrates that have a nitrogen atom, graphene loss occurs. Although this phenomenon has remained a hurdle for over a decade, restricting the advantages of applying graphene in the growth of III-nitride materials, few previous studies have been conducted. Here, we report the stability of graphene on substrates containing oxygen or nitrogen atoms. Graphene has been observed on highly decomposed Al2O3; however, graphene loss occurred on decomposed AlN at temperatures over 1300 °C. To overcome graphene loss, we investigated 2-D hexagonal boron nitride (h-BN) as an alternative. Unlike graphene on AlN, it was confirmed that h-BN on AlN was intact after the same high-temperature process. Moreover, the overgrown AlN layers on both h-BN/AlN and h-BN/Al2O3could be successfully exfoliated, which indicates that 2-D h-BN survived after AlN growth and underlines its availability for the vdWE/RE of III-nitrides with further mechanical transfer. By enhancing the stability of the 2-D material on the substrate, our study provides insights into the realization of a novel epitaxy concept.

    DOI: 10.1039/d1sc01642c

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  45. Etching-induced damage in heavily Mg-doped p-type GaN and its suppression by low-bias-power inductively coupled plasma-reactive ion etching

    Kumabe Takeru, Ando Yuto, Watanabe Hirotaka, Deki Manato, Tanaka Atsushi, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   60 巻 ( SB ) 頁: SBBD03   2021年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    Inductively coupled plasma–reactive ion etching (ICP–RIE)-induced damage in heavily Mg-doped p-type GaN ([Mg] = 2 × 1019 cm−3) was investigated by low-temperature photoluminescence (PL) and depth-resolved cathodoluminescence (CL) spectroscopy. From PL measurements, we found broad yellow luminescence (YL) with a maximum at around 2.2–2.3 eV, whose origin was considered to be isolated nitrogen vacancies (VN), only in etched samples. The depth-resolved CL spectroscopy revealed that the etching-induced YL was distributed up to the electron-beam penetration depth of around 200 nm at a high ICP–RIE bias power (Pbias). Low-bias-power (low-Pbias) ICP–RIE suppressed the YL and its depth distribution to levels similar to those of an unetched sample, and a current–voltage characteristic comparable to that of an unetched sample was obtained for a sample etched with Pbias of 2.5 W.

    DOI: 10.35848/1347-4065/abd538

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  46. Impact of heat treatment process on threshold current density in AlGaN-based deep-ultraviolet laser diodes on AlN substrate

    Kushimoto Maki, Zhang Ziyi, Sugiyama Naoharu, Honda Yoshio, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   14 巻 ( 5 ) 頁: 051003   2021年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    The electroluminescence (EL) uniformity of AlGaN-based deep UV laser diodes on AlN substrate was analyzed by using the EL imaging technique. Although nonuniform EL patterns were observed, the uniformity was improved by changing the position of the p-electrode. The threshold current density was also reduced by suppressing the inhomogeneity of the EL. Cathodoluminescence analysis revealed that the cause of the non-uniformity is the degradation of the active layer and the nonuniformity emission formed by rapid thermal annealing at high temperature after mesa structure formation.

    DOI: 10.35848/1882-0786/abf443

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  47. Micro-Light Emitting Diode: From Chips to Applications

    Parbrook Peter J., Corbett Brian, Han Jung, Seong Tae-Yeon, Amano Hiroshi

    LASER & PHOTONICS REVIEWS   15 巻 ( 5 ) 頁: 2000133   2021年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Laser and Photonics Reviews  

    Typical light-emitting diodes (LEDs) have a form factor >(300 × 300) µm2. Such LEDs are commercially mature in illumination and ultralarge displays. However, recent LED research includes shrinking individual LED sizes from side lengths >300 µm to values <100 µm, leading to devices called micro-LEDs. Their advent creates a number of exciting new application spaces. Here, a review of the principles and applications of micro-LED technology is presented. In particular, the implications of reduced LED size in necessitating mitigation strategies for nonradiative device edge damage as well as the potential for higher drive current densities are discussed. The opportunities to integrate micro-LEDs with electronics, and into large-scale arrays, allow pixel addressable scalable integrated displays, while the small micro-LED size is ideal for high-speed modulation for visible light communication, and for integration into biological systems as part of optogenetic therapies.

    DOI: 10.1002/lpor.202000133

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  48. Discrete AlN mole fraction of n/12 (n = 4-8) in Ga-rich zones functioning as electron pathways created in nonflat AlGaN layers grown on high-miscut sapphire substrates

    Nagasawa Y., Hirano A., Ippommatsu M., Sako H., Hashimoto A., Sugie R., Honda Y., Amano H., Akasaki I., Kojima K., Chichibu S.F.

    Journal of Applied Physics   129 巻 ( 16 ) 頁: 164503   2021年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    Ga-rich zones created along macrosteps in n-AlGaN plausibly function as electron pathways of AlGaN-based deep-ultraviolet (DUV) LEDs fabricated on AlN templates using 1.0°-miscut c(0001) sapphire substrates toward the m[1-100] axis. This work was performed to clarify AlN mole fractions (xAl) of Ga-rich zones. xAl ≃ (7/12, 6/12, and 5/12) was observed in Ga-rich zones in AlαGa1−αN (α ≃ 0.63, 0.55, and 0.43, respectively) by the method proposed in our previous article in which we showed that Ga-rich zones of Al8/12Ga4/12N were created in Al0.7Ga0.3N. xAl in the Ga-rich zones obtained from an energy-dispersive x-ray signal by scanning transmission electron microscopy calibrated by Rutherford backscattering well agreed with xAl obtained by cross-sectional cathodoluminescence (CL) spectroscopy using scanning electron microscopy. A weak CL shoulder peak corresponding to Al4/12Ga8/12N was also observed for Al0.43Ga0.57N. In addition, xAl ≃ n/12 (n = 6-9) in Al-rich zones appeared in the rest of the Ga-rich zones. Furthermore, nanobeam electron diffraction patterns of the Ga-rich zones indicated a high possibility of a regular configuration of Ga and Al atoms on the c(0001) plane in our samples. Consequently, xAl values in nonflat AlGaN layers with macrosteps were often determined to be near n/12 (n: integer). Thus, Ga-rich zones (xAl = n/12: n = 4-8) formed in our nonflat AlGaN layers, which originated from the macrosteps along [11-20] edgelines normal to the m[1-100] axis, are suggested to be metastable. The creation of discrete xAl in Ga-rich zones should contribute to the stable production of DUV-LEDs using high-miscut sapphire substrates.

    DOI: 10.1063/5.0042036

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  49. Experimental demonstration of GaN IMPATT diode at X-band

    Kawasaki Seiya, Ando Yuto, Deki Manato, Watanabe Hirotaka, Tanaka Atsushi, Nitta Shugo, Honda Yoshio, Arai Manabu, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   14 巻 ( 4 ) 頁: 046501   2021年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We report the first experimental demonstration of microwave oscillation in GaN impact ionization avalanche time transit (IMPATT) diodes at the X-band. The device used in this study is a single drift diode with a p+–n simple abrupt junction and vertical mesa termination. The reverse I–V characteristic of the diode shows low leakage current, clear avalanche breakdown, and high avalanche capability, as required for IMPATT operation. Microwave testing is performed in an X-band waveguide circuit with a reduced-height waveguide resonant cavity. Oscillations are observed at 9.52 GHz at a power of ∼56 mW.

    DOI: 10.35848/1882-0786/abe3dc

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  50. Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes

    Sim Kee-Baek, Kim Su-Kyung, Lee Hwa-Seub, Lee Sang-Youl, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   10 巻 ( 4 ) 頁: 045005   2021年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    We optimized Ni/Ag-based p-type reflectors for the improvement of efficiency of 273 nm deep ultraviolet (DUV) AlGaN-based flip-chip light emitting diodes (FCLEDs). The Ni(3 nm)/Ag(5-15 nm)/Al/Ni and Ni(25-50 nm)/Ag/Ni contacts exhibited higher reflectance (36.4-39.5%) at 273 nm than reference Ni(5 nm)/Au(5 nm)/Al/Ni contact (26.1%). The Ni(3 nm)/Ag/Al(200 nm)/Ni(20 nm) and Ni/Ag(200 nm)/Ni(20 nm)-based FCLEDs gave forward voltages in the rage of 6.93-7.11 V and 5.5-6.28 V at 20 mA, respectively, whereas the Ni/Au-based sample showed 6.35 V. Further, the Ni(3 nm)/Ag(10 nm)/Al/Ni-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples exhibited 4.85% and 13.4% larger output power at 1.2 W than the reference sample. The Ni(3 nm)/Ag(10 nm)-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples produced 5.6% and 8.5% higher peak external quantum efficiency than the reference sample. It was further shown that the Ni(3 nm)/Ag(10 nm)/Al/Ni-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples experienced less efficiency droop (namely, 27.9 and 26.4%, respectively) than the reference sample (31.4%). Based on the scanning transmission electron microscopy and X-ray photoemission spectroscopy results, the ohmic formation mechanism is described and discussed.

    DOI: 10.1149/2162-8777/abf49b

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  51. Numerical Simulation of Ammonothermal Crystal Growth of GaN-Current State, Challenges, and Prospects

    Schimmel Saskia, Tomida Daisuke, Ishiguro Tohru, Honda Yoshio, Chichibu Shigefusa, Amano Hiroshi

    CRYSTALS   11 巻 ( 4 ) 頁: 356   2021年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Crystals  

    Numerical simulations are a valuable tool for the design and optimization of crystal growth processes because experimental investigations are expensive and access to internal parameters is limited. These technical limitations are particularly large for ammonothermal growth of bulk GaN, an important semiconductor material. This review presents an overview of the literature on simulations targeting ammonothermal growth of GaN. Approaches for validation are also reviewed, and an overview of available methods and data is given. Fluid flow is likely in the transitional range between laminar and turbulent; however, the time-averaged flow patterns likely tend to be stable. Thermal boundary conditions both in experimental and numerical research deserve more detailed evaluation, especially when designing numerical or physical models of the ammonothermal growth system. A key source of uncertainty for calculations is fluid properties under the specific conditions. This originates from their importance not only in numerical simulations but also in designing similar physical model systems and in guiding the selection of the flow model. Due to the various sources of uncertainty, a closer integration of numerical modeling, physical modeling, and the use of measurements under ammonothermal process conditions appear to be necessary for developing numerical models of defined accuracy.

    DOI: 10.3390/cryst11040356

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  52. Strain-induced yellow to blue emission tailoring of axial InGaN/GaN quantum wells in GaN nanorods synthesized by nanoimprint lithography

    Avit Geoffrey, Robin Yoann, Liao Yaqiang, Nan Hu, Pristovsek Markus, Amano Hiroshi

    SCIENTIFIC REPORTS   11 巻 ( 1 ) 頁: 6754   2021年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    GaN nanorods (NRds) with axial InGaN/GaN MQWs insertions are synthesized by an original cost-effective and large-scale nanoimprint-lithography process from an InGaN/GaN MQWs layer grown on c-sapphire substrates. By design, such NRds exhibit a single emission due to the c-axis MQWs. A systematic study of the emission of the NRds by time-resolved luminescence (TR-PL) and power dependence PL shows a diameter-controlled luminescence without significant degradation of the recombination rate thanks to the diameter-controlled strain tuning and QSCE. A blueshift up to 0.26 eV from 2.28 to 2.54 eV (543 nm to 488 nm) is observed for 3.2 nm thick InGaN/GaN QWs with an In composition of 19% when the NRds radius is reduced from 650 to 80 nm. The results are consistent with a 1-D based strain relaxation model. By combining state of the art knowledge of c-axis growth and the strong strain relieving capability of NRds, this process enables multiple and independent single-color emission from a single uniform InGaN/GaN MQWs layer in a single patterning step, then solving color mixing issue in InGaN based nanorods LED devices.

    DOI: 10.1038/s41598-021-86139-9

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  53. Progress in Modeling Compound Semiconductor Epitaxy: Unintentional Doping in GaN MOVPE

    Kangawa Yoshihiro, Kusaba Akira, Kempisty Pawel, Shiraishi Kenji, Nitta Shugo, Amano Hiroshi

    CRYSTAL GROWTH & DESIGN   21 巻 ( 3 ) 頁: 1878 - 1890   2021年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Crystal Growth and Design  

    To improve the properties of semiconductors, it is necessary to construct an integrated crystal growth model that covers all elementary processes of metal-organic vapor phase epitaxy (MOVPE). Although there are several theoretical models that can reproduce any elemental growth process, they are inadequate for controlling semiconductor epitaxy: the elementary processes of (1) the vapor phase reaction, (2) the surface reaction, and (3) incorporation are entangled with each other. That is, sequential analyses of elementary growth processes from upstream (1) to downstream (3) are indispensable for an understanding of the entire process of MOVPE. In this Review, the recent progress of theoretical models based on calculations from first-principles calculations are summarized. The possibility of predicting carbon concentrations in GaN grown by MOVPE are explored as an example. The results of calculations using a model that integrates (1) → (2) → (3) reproduce the experimental tendencies of carbon incorporation. Calculations show that the contribution of each elementary growth process to a change in carbon concentration can be discussed separately, but the relationship between the input parameters and the resulting outputs can only be determined through experiment. Although this examination explores a special case, the development of a precise integrated crystal growth model would greatly contribute to innovation in semiconductor manufacturing.

    DOI: 10.1021/acs.cgd.0c01564

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  54. Fabrication of GaN cantilever on GaN substrate by photo-electrochemical etching

    Yamada Takehiro, Ando Yuto, Watanabe Hirotaka, Furusawa Yuta, Tanaka Atsushi, Deki Manato, Nitta Shugo, Honda Yoshio, Suda Jun, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   14 巻 ( 3 ) 頁: 036505   2021年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Photo-electrochemical (PEC) etching is a promising technique for fabricating GaN microelectromechanical systems devices. In this study, we demonstrate the fabrication of GaN cantilevers by the bandgap-selective PEC etching of an InGaN superlattice sacrificial layer. By using an InGaN superlattice as a sacrifice layer, we found the PEC etching rate became higher than using a normal InGaN layer. As a result, the InGaN superlattice was completely etched and we fabricated GaN-based cantilevers whose resonance characteristics were measured. The Young’s modulus of GaN was determined from the resonance characteristics of GaN cantilevers to be the same as the highest value reported previously.

    DOI: 10.35848/1882-0786/abe657

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  55. Boundary Conditions for Simulations of Fluid Flow and Temperature Field during Ammonothermal Crystal Growth-A Machine-Learning Assisted Study of Autoclave Wall Temperature Distribution

    Schimmel Saskia, Tomida Daisuke, Saito Makoto, Bao Quanxi, Ishiguro Toru, Honda Yoshio, Chichibu Shigefusa, Amano Hiroshi

    CRYSTALS   11 巻 ( 3 ) 頁: 1 - 27   2021年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Crystals  

    Thermal boundary conditions for numerical simulations of ammonothermal GaN crystal growth are investigated. A global heat transfer model that includes the furnace and its surroundings is presented, in which fluid flow and thermal field are treated as conjugate in order to fully account for convective heat transfer. The effects of laminar and turbulent flow are analyzed, as well as those of typically simultaneously present solids inside the autoclave (nutrient, baffle, and multiple seeds). This model uses heater powers as a boundary condition. Machine learning is applied to efficiently determine the power boundary conditions needed to obtain set temperatures at specified locations. Typical thermal losses are analyzed regarding their effects on the temperature distribution inside the autoclave and within the autoclave walls. This is of relevance because autoclave wall temperatures are a convenient choice for setting boundary conditions for simulations of reduced domain size. Based on the determined outer wall temperature distribution, a simplified model containing only the autoclave is also presented. The results are compared to those observed using heater-long fixed temperatures as boundary condition. Significant deviations are found especially in the upper zone of the autoclave due to the important role of heat losses through the autoclave head.

    DOI: 10.3390/cryst11030254

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  56. Development of Pulsed TEM Equipped with Nitride Semiconductor Photocathode for High-Speed Observation and Material Nanofabrication

    Yasuda Hidehiro, Nishitani Tomohiro, Ichikawa Shuhei, Hatanaka Shuhei, Honda Yoshio, Amano Hiroshi

    QUANTUM BEAM SCIENCE   5 巻 ( 1 ) 頁: 5   2021年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Quantum Beam Science  

    The development of pulsed electron sources is applied to electron microscopes or electron beam lithography and is effective in expanding the functions of such devices. The laser photocathode can generate short pulsed electrons with high emittance, and the emittance can be increased by changing the cathode substrate from a metal to compound semiconductor. Among the substrates, nitride-based semiconductors with a negative electron affinity (NEA) have good advantages in terms of vacuum environment and cathode lifetime. In the present study, we report the development of a photocathode electron gun that utilizes photoelectron emission from a NEA-InGaN substrate by pulsed laser excitation, and the purpose is to apply it to material nanofabrication and high-speed observation using a pulsed transmission electron microscope (TEM) equipped with it.

    DOI: 10.3390/qubs5010005

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  57. Suppression of the regrowth interface leakage current in AlGaN/GaN HEMTs by unactivated Mg doped GaN layer

    Liu T., Watanabe H., Nitta S., Wang J., Yu G., Ando Y., Honda Y., Amano H., Tanaka A., Koide Y.

    APPLIED PHYSICS LETTERS   118 巻 ( 7 ) 頁: 072103   2021年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    The leakage current caused by the Si pileup at the regrowth interface of AlGaN/GaN high electron mobility transistors (HEMTs) is significantly suppressed by the semi-insulating Mg-doped GaN layer. Mg is unintentionally doped and can be originated from the graphite susceptor of metal organic vapor phase epitaxy. Before regrowth of the AlGaN/GaN heterostructure, the GaN template is treated with hydrochloric acid (HCl) and hydrogen peroxide/potassium hydroxide (H2O2/KOH) solution to promote the adsorption of Mg on the GaN surface. The Mg-doped GaN channel layer is highly resistive due to the passivation of hydrogen. The p-n junction formed by the weakly p-type Mg-doped GaN layer and the n-type Si pileup layer depletes the excess electrons at the regrowth interface. As a result, the off-state drain leakage current of the HEMT device can be decreased by two orders of magnitude at 40 V.

    DOI: 10.1063/5.0034584

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  58. Optical properties of neodymium ions in nanoscale regions of gallium nitride (vol 10, pg 2614, 2020)

    Sato Shin-Ichiro, Deki Manato, Watanabe Hirotaka, Nitta Shugo, Honda Yoshio, Nishimura Tomoaki, Gibson Brant C., Greentree Andrew D., Amano Hiroshi, Ohshima Takeshi

    OPTICAL MATERIALS EXPRESS   11 巻 ( 2 ) 頁: 524 - 524   2021年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Optical Materials Express  

    We correct an error in the Eq. (1).

    DOI: 10.1364/OME.420328

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  59. Generalized Frequency Dependent Small Signal Model for High Frequency Analysis of AlGaN/GaN MOS-HEMTs

    Jadhav A., Ozawa T., Baratov A., Asubar J.T., Kuzuhara M., Wakejima A., Yamashita S., Deki M., Honda Y., Roy S., Amano H., Sarkar B.

    IEEE Journal of the Electron Devices Society   9 巻   頁: 570 - 581   2021年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Journal of the Electron Devices Society  

    Traditional lumped small signal equivalent circuit models of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) are made up of constant valued circuit elements. Such models are unable to capture the high frequency behavior (above 20 GHz) of the device. In this work, a modified small signal equivalent circuit model of AlGaN/GaN MOS-HEMTs is presented. The key feature of the proposed model is that the values of the different circuit elements in the model are considered to be frequency dependent in nature and not constants. The frequency dependent value of each circuit element is mathematically represented using polynomial functions where the coefficients of the functions are determined via a least-square curve fitting approach. This frequency dependent attribute of the circuit element values ensures that the proposed model is very accurate at high frequencies without sacrificing the compactness of the model topology. The accuracy of the proposed model has been verified up to 50 GHz using experimentally measured Y-parameters of AlGaN/GaN MOS-HEMTs having a different gate dielectric and gate length.

    DOI: 10.1109/JEDS.2021.3081463

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  60. Development of UV-C laser diodes on AlN substrate

    Kushimoto M.

    Proceedings of SPIE - The International Society for Optical Engineering   11686 巻   2021年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering  

    DOI: 10.1117/12.2575872

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  61. Decrease in the injection efficiency and generation of midgap states in UV-C LEDs: A model based on rate equations

    Piva F.

    Proceedings of SPIE - The International Society for Optical Engineering   11686 巻   2021年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering  

    DOI: 10.1117/12.2578134

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  62. 3D GaN Power Switching Electronics: A Revival of Interest in ELO

    Wang Jia, Amano Hiroshi, Xie Ya-Hong

    2021 5TH IEEE ELECTRON DEVICES TECHNOLOGY & MANUFACTURING CONFERENCE (EDTM)     2021年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:2021 5th IEEE Electron Devices Technology and Manufacturing Conference, EDTM 2021  

    We reported the first-time utilization of ELO (epitaxial lateral overgrowth) GaN (gallium nitride) for power diodes. The undesired stage of coalescence related to ELO is avoided by virtue of a novel 3D device architecture built on the ELO GaN islands on foreign substrate which features pure-lateral p-n and n+ -n-junctions and electrodes lying on the opposing sidewalls of the island. Excellent electrical performance was demonstrated, revealing a strong potential of ELO GaN with 3D device architecture for power switching applications.

    DOI: 10.1109/EDTM50988.2021.9420859

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  63. Electrical properties of GaN metal-insulator-semiconductor field-effect transistors with Al2O3/GaN interfaces formed on vicinal Ga-polar and nonpolar surfaces

    Ando Yuto, Nagamatsu Kentaro, Deki Manato, Taoka Noriyuki, Tanaka Atsushi, Nitta Shugo, Honda Yoshio, Nakamura Tohru, Amano Hiroshi

    APPLIED PHYSICS LETTERS   117 巻 ( 24 ) 頁: 242104   2020年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/5.0028516

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  64. The 2020 UV emitter roadmap

    Amano H., Collazo R., De Santi C., Einfeldt S., Funato M., Glaab J., Hagedorn S., Hirano A., Hirayama H., Ishii R., Kashima Y., Kawakami Y., Kirste R., Kneissl M., Martin R., Mehnke F., Meneghini M., Ougazzaden A., Parbrook P.J., Rajan S., Reddy P., Römer F., Ruschel J., Sarkar B., Scholz F., Schowalter L.J., Shields P., Sitar Z., Sulmoni L., Wang T., Wernicke T., Weyers M., Witzigmann B., Wu Y.R., Wunderer T., Zhang Y.

    Journal of Physics D: Applied Physics   53 巻 ( 50 ) 頁: 503001   2020年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    Solid state UV emitters have many advantages over conventional UV sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down to 210 nm - due to its large and tuneable direct band gap, n- and p-doping capability up to the largest bandgap material AlN and a growth and fabrication technology compatible with the current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer from numerous challenges compared to their visible counterparts that become most obvious by consideration of their light output power, operation voltage and long term stability. Most of these challenges are related to the large bandgap of the materials. However, the development since the first realization of UV electroluminescence in the 1970s shows that an improvement in understanding and technology allows the performance of UV emitters to be pushed far beyond the current state. One example is the very recent realization of edge emitting laser diodes emitting in the UVC at 271.8 nm and in the UVB spectral range at 298 nm. This roadmap summarizes the current state of the art for the most important aspects of UV emitters, their challenges and provides an outlook for future developments.

    DOI: 10.1088/1361-6463/aba64c

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  65. Detailed analysis of Ga-rich current pathways created in an n-Al<inf>0.7</inf>Ga<inf>0.3</inf>N layer grown on an AlN template with dense macrosteps

    Nagasawa Y., Hirano A., Ippommatsu M., Sako H., Hashimoto A., Sugie R., Honda Y., Amano H., Akasaki I., Kojima K., Chichibu S.F.

    Applied Physics Express   13 巻 ( 12 ) 頁: 124001   2020年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    To clarify the behavior of the AlGaN in 20 nm wide Ga-rich current pathways in an n-AlGaN layer, which assists carrier localization in AlGaN-based light-emitting diodes, we performed a detailed analysis using an n-Al0.7Ga0.3N layer on AlN with dense macrosteps on a 1.0 miscut sapphire substrate. Energy-dispersive X-ray spectra, obtained using cross-sectional scanning transmission electron microscopy calibrated by Rutherford backscattering and cross-sectional cathodoluminescence spectra, indicated that AlN mole fraction in the Ga-rich current pathways was nearly ∼2/3. This result is consistent with those of other research groups, suggesting that metastable Al2/3Ga1/3N is created in Ga-rich current pathways.

    DOI: 10.35848/1882-0786/abcb49

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  66. Surface passivation of light emitting diodes: From nano-size to conventional mesa-etched devices

    Seong Tae-Yeon, Amano Hiroshi

    SURFACES AND INTERFACES   21 巻   頁: 100765   2020年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Surfaces and Interfaces  

    III-V compound semiconductor-based light emitting devices (LEDs) operating in ultraviolet to visible wavelength ranges are greatly important for their applications, including displays, solid-state lighting, biomedical applications, optogenetics, and high bandwidth visible light communications. The performance of such LEDs is unavoidably affected by the surface characteristics of semiconductor layers. In particular, for LEDs, plasma-etching processes are inevitably adopted to define mesas, via holes and waveguides. The presence of surface defects is exceedingly detrimental to the device performance. It is therefore vital to understand the passivation mechanisms and approaches in order to control and so to maximize the efficiency. Here, we review recent progress in the surface treatment and passivation of III-V compound semiconductors-based LEDs. We show how different types of passivation approaches, including treatments with aqueous solutions, dielectric materials, or combination of both, affect the surface states and plasma-induced defects and hence the electrical and optical performance of LEDs.

    DOI: 10.1016/j.surfin.2020.100765

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  67. State-of-the-art and prospects for intense red radiation from core-shell InGaN/GaN nanorods

    Evropeitsev Evgenii A., Kazanov Dmitrii R., Robin Yoann, Smirnov Alexander N., Eliseyev Ilya A., Davydov Valery Yu., Toropov Alexey A., Nitta Shugo, Shubina Tatiana V., Amano Hiroshi

    SCIENTIFIC REPORTS   10 巻 ( 1 ) 頁: 19048   2020年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    Core–shell nanorods (NRs) with InGaN/GaN quantum wells (QWs) are promising for monolithic white light-emitting diodes and multi-color displays. Such applications, however, are still a challenge because intensity of the red band is too weak compared with blue and green. To clarify this problem, we measured photoluminescence of different NRs, depending on power and temperature, as well as with time resolution. These studies have shown that dominant emission bands come from nonpolar and semipolar QWs, while a broad yellow-red band arises mainly from defects in the GaN core. An emission from polar QWs located at the NR tip is indistinguishable against the background of defect-related luminescence. Our calculations of electromagnetic field distribution inside the NRs show a low density of photon states at the tip, which additionally suppresses the radiation of polar QWs. We propose placing polar QWs inside a cylindrical part of the core, where the density of photon states is higher and the well area is much larger. Such a hybrid design, in which the excess of blue radiation from shell QWs is converted to red radiation in core wells, can help solve the urgent problem of red light for many applications of NRs.

    DOI: 10.1038/s41598-020-76042-0

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  68. Limitation of simple np-n tunnel junction based LEDs grown by metal-organic vapor phase epitaxy

    Robin Y., Bournet Q., Avit G., Pristovsek M., Andre Y., Trassoudaine A., Amano H.

    SEMICONDUCTOR SCIENCE AND TECHNOLOGY   35 巻 ( 11 ) 頁: 115005   2020年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Semiconductor Science and Technology  

    We show evidence that tunnel junctions (TJs) in GaN grown by metal-organic vapor phase epitaxy are dominated by defect level-assisted tunneling. This is in contrast with the common belief that highly doped layers (>1020 cm−3) are required to narrow the TJ space charge region and promote the band-to-band tunneling. Our conclusion stems from the study and the review of the major doping limitations of carefully optimized p++ and n++ layers. The secondary ions mass spectroscopy profiles of GaN based TJ LEDs show a strong oxygen concentration located close to the p++/n++ interface, typical for three dimensional growth. In addition, considering the doping limitation asymmetry and Mg carry-over, our simulations indicate a depletion region of more than 10 nm which is buried in a rough and defective n++ layer. However, decent electrical characteristics of the studied TJ based LEDs are obtained, with a low penalty voltage of 1.1 V and a specific differential resistance of about 10-2 Ω.cm2 at 20 mA. This indicates that a common TJ could be greatly optimized by using a moderate doping (∼1019 cm−3) while intentionally introducing local defects within the TJ.

    DOI: 10.1088/1361-6641/abad73

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  69. Modeling the degradation mechanisms of AlGaN-based UV-C LEDs: from injection efficiency to mid-gap state generation

    Piva F., De Santi C., Deki M., Kushimoto M., Amano H., Tomozawa H., Shibata N., Meneghesso G., Zanoni E., Meneghini M.

    PHOTONICS RESEARCH   8 巻 ( 11 ) 頁: 1786 - 1791   2020年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Photonics Research  

    In this work, we analyze and model the effect of a constant current stress on an ultraviolet light-emitting diode with a nominal wavelength of 285 nm. By carrying out electrical, optical, spectral, and steady-state photocapacitance (SSPC) analysis during stress, we demonstrate the presence of two different degradation mechanisms. The first one occurs in the first 1000 min of stress, is ascribed to the decrease in the injection efficiency, and is modeled by considering the defect generation dynamics related to the de-hydrogenation of gallium vacancies, according to a system of three differential equations; the second one occurs after 1000 min of stress and is correlated with the generation of mid-gap defects, for which we have found evidence in the SSPC measurements. Specifically, we detected the presence of deep-level states (at 1.6 eV) and mid-gap states (at 2.15 eV), indicating that stress induces the generation of non-radiative recombination centers.

    DOI: 10.1364/PRJ.401785

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  70. Epitaxial Combination of Two-Dimensional Hexagonal Boron Nitride with Single-Crystalline Diamond Substrate

    Yang Xu, Pristovsek Markus, Nitta Shugo, Liu Yuhuai, Honda Yoshio, Koide Yasuo, Kawarada Hiroshi, Amano Hiroshi

    ACS APPLIED MATERIALS & INTERFACES   12 巻 ( 41 ) 頁: 46466 - 46475   2020年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACS applied materials &amp; interfaces  

    Hexagonal boron nitride (hBN) and diamond are promising materials for next-generation electronics and optoelectronics. However, their combination is rarely reported. In this study, we for the first time demonstrate the success to direct growth of two-dimensional (2D) hBN crystal layers on diamond substrates by metalorganic vapor phase epitaxy. Compared with the disordered growth we found on diamond (100), atomic force microscopy, X-ray diffraction, and transmission electron microscopy results all support 2D hBN with highly oriented lattice formation on diamond (111). Also, the epitaxial relationship between hBN and diamond (111) substrate is revealed to be [0 0 0 1]hBN // [1 1 1]diamond and [1 0 1̅ 0]hBN // [1 1 2̅]diamond. The valence band offset at hBN/diamond (111) heterointerface determined by X-ray photoelectron spectroscopy is 1.4 ± 0.2 eV, thus yielding a conduction band offset of 1.0 ± 0.2 eV and type II staggered band alignment with a bandgap of 5.9 eV assumed for hBN. Furthermore, prior thermal cleaning of diamond in a pure H2 atmosphere smoothens the surface for well-ordered layered hBN epitaxy, while thermal cleaning in a mixed H2 and NH3 atmosphere etches the diamond surface, creating many small faceted pits that destroy the following epitaxy of hBN.

    DOI: 10.1021/acsami.0c11883

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    PubMed

  71. Space charge profile study of AlGaN-based p-type distributed polarization doped claddings without impurity doping for UV-C laser diodes

    Zhang Ziyi, Kushimoto Maki, Horita Masahiro, Sugiyama Naoharu, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi

    APPLIED PHYSICS LETTERS   117 巻 ( 15 ) 頁: 152104   2020年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    The space charge density profile of the nondoped AlGaN-based p-type cladding layer for UV-C laser diodes realized by distributed polarization doping is examined theoretically and experimentally. The analysis of the capacitance-voltage measurement revealed that the average effective acceptor density of 4.2×1017 cm-3 is achieved even without impurity doping, and it is in good agreement with the theoretical prediction from the measured Al composition profile. This result suggests that the cladding layer is ideal for UV-C LDs because it provides sufficient hole injection while potentially avoiding internal losses due to impurity doping.

    DOI: 10.1063/5.0027789

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  72. Optical properties of neodymium ions in nanoscale regions of gallium nitride

    Sato S.I., Deki M., Watanabe H., Nitta S., Honda Y., Nishimura T., Gibson B.C., Greentree A.D., Amano H., Ohshima T.

    Optical Materials Express   10 巻 ( 10 ) 頁: 2614 - 2623   2020年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Optical Materials Express  

    Wide bandgap semiconductors are increasingly important for bioimaging applications, as they can possess good biocompatibility and host a large range of fluorescent defects spanning the visible to infrared. Gallium nitride is one promising host for photostable fluorophores. In particular, neodymium (Nd)-doped gallium nitride (GaN) shows bright near-infrared fluorescence and narrow room temperature linewidth and is therefore a candidate material for fluorescent probes for bioimaging. To explore the conditions necessary to generate biomarkers based on Nd:GaN, this paper reports the room temperature photoluminescence (PL) properties of small ensembles of Nd ions implanted into the nanoscale regions of GaN epilayers. The minimum volume of Nd-implanted GaN that can be optically detected in this study is about 8×104 nm3 and the minimum detected ensemble of Nd ions is about 4×103, although not all of implanted Nd ions activate as luminescence centers. We show from the PL excitation spectra that the strongest resonant excitation appears at 619 nm, attributed to the 4I9/2 → 4G5/2 (4G7/2) transition in the 4f -shell. We measure the luminescence lifetime to be several tens of microseconds. We also identify the presence of a different excitation mechanism from the resonant excitation when excited below 510 nm (above 2.43 eV).

    DOI: 10.1364/OME.401765

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  73. Single-chip imaging system that simultaneously transmits light

    Wang Y., Gao X., Fu K., Qin F., Zhu H., Liu Y., Amano H.

    Applied Physics Express   13 巻 ( 10 )   2020年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Multiple-quantum-well diodes (MQW diodes) naturally have key functionalities of light emission, transmission, modulation and detection all at the same time, enabling new forms of information and energy conversion between photons and electrons. When approximately biased and illuminated at the same time, a multifunctional MQW diode allows simultaneous light emission and detection within a single diode. A single-chip imaging system that uses a 4 × 4 MQW diode array is experimentally demonstrated here that can simultaneously transmit light and capture an image, showing the great development potential of advanced monolithic III-nitride information systems.

    DOI: 10.35848/1882-0786/abb786

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  74. WPTシステム実現のための 高周波GaNパワーデバイス 招待有り 査読有り

    天野 浩

    電子情報通信学会誌 IEICE誌   103 巻 ( 10 ) 頁: 1016 - 1022   2020年10月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    その他リンク: https://www.journal.ieice.org/bin/pdf_link.php?fname=k103_10_1016&lang=J&year=2020

  75. Single-chip imaging system that simultaneously transmits light

    Wang Yongjin, Gao Xumin, Fu Kang, Qin Feifei, Zhu Hongbo, Liu Yuhuai, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   13 巻 ( 10 )   2020年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  76. Photoluminescence properties of implanted Praseodymium into Gallium Nitride at elevated temperatures

    Sato S.i., Deki M., Nishimura T., Okada H., Watanabe H., Nitta S., Honda Y., Amano H., Ohshima T.

    Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms   479 巻   頁: 7 - 12   2020年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms  

    Since Rare-Earth (RE) doped Gallium Nitride (GaN) is expected to be used as electrically driven single photon source at room temperature, low dose RE-ion implantation and their activation as luminescent centers are of interest. This paper reports photoluminescence (PL) properties of Praseodymium (Pr) implanted GaN at different temperatures ranging from room temperature to 1200 °C. All the Pr-implanted GaN samples are thermally annealed after implantation and show strong PL emissions at 650.2 nm and 652.0 nm, originated from 3P0→3F2 transition in 4f-shell of Pr3+ ions. It is shown that the PL intensity originating from Pr3+ ions is reduced as the implantation temperature increases for the Pr-implanted samples annealed at 1200 °C. This result suggests that Pr3+ ions quench due to the formation of complex defects and defect clusters. The effect of high temperature implantation on the recovery of GaN crystallinity is discussed in terms of critical dose and displacement damage.

    DOI: 10.1016/j.nimb.2020.06.007

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  77. Low interface state densities at Al2O3/GaN interfaces formed on vicinal polar and non-polar surfaces

    Ando Yuto, Nagamatsu Kentaro, Deki Manato, Taoka Noriyuki, Tanaka Atsushi, Nitta Shugo, Honda Yoshio, Nakamura Tohru, Amano Hiroshi

    APPLIED PHYSICS LETTERS   117 巻 ( 10 ) 頁: 102012   2020年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    Ni/Al2O3/GaN structures with vicinal GaN surfaces from the c- or m-plane were formed. Then, electrical interface properties of the structures were systematically investigated. It was found that interface state density (Dit) at the Al2O3/GaN interface for the c-plane is higher than that for the m-plane, and post-metallization annealing is quite effective to reduce Dit for both c- and m-planes. As a result, the low Dit value of ∼3 × 1010 eV-1 cm-2 was demonstrated for both planes.

    DOI: 10.1063/5.0010774

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  78. Design and characterization of a low-optical-loss UV-C laser diode

    Zhang Z., Kushimoto M., Sakai T., Sugiyama N., Schowalter L.J., Sasaoka C., Amano H.

    Japanese Journal of Applied Physics   59 巻 ( 9 )   2020年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    We present an optical modeling and characterization study of prototype ultraviolet laser diode (LD) structures grown on single-crystal AlN substrates, with focus on the reduction of modal loss caused by optical mode coupling to the absorptive layers on the p-side (i.e. p-contact and p-metal layers). The transparent AlN substrates enabled optical pumping for measuring modal loss without requiring functioning LDs. The modal loss measured in this way was in good agreement with electrically evaluated results of processed LDs, and both results were consistent with optical modeling predictions. By using 0.32 μm thick p-side cladding, we were able to suppress the modal loss of the designed LD structure to 8.4 cm-1, where the contribution from the absorptive p-contact layers was less than 3 cm-1.

    DOI: 10.35848/1347-4065/abaac6

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  79. Design and characterization of a low-optical-loss UV-C laser diode

    Zhang Ziyi, Kushimoto Maki, Sakai Tadayoshi, Sugiyama Naoharu, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   59 巻 ( 9 )   2020年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  80. Increasing the Luminescence Efficiency of Long-Wavelength (In,Ga)N Quantum Well Structures by Electric Field Engineering Using an (Al,Ga)N Capping Layer

    Vichi Stefano, Robin Yoann, Sanguinetti Stefano, Pristovsek Markus, Amano Hiroshi

    PHYSICAL REVIEW APPLIED   14 巻 ( 2 ) 頁: 024018   2020年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevApplied.14.024018

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  81. Thermodynamic analysis of the gas phase reaction of Mg-doped GaN growth by HVPE using MgO

    Kimura T., Ohnishi K., Amano Y., Fujimoto N., Araidai M., Nitta S., Honda Y., Amano H., Kangawa Y., Shiraishi K.

    Japanese Journal of Applied Physics   59 巻 ( 8 ) 頁: 088001   2020年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    The halide vapor phase epitaxy (HVPE) of Mg-doped GaN using solid MgO is investigated. Thermodynamic analysis of the reactions amongst MgO, HCl and N2 is performed based on first-principles calculations. It is found that the equilibrium partial pressure of MgCl2 is the highest amongst magnesium related molecules at 900 °C. By increasing the input partial pressure of HCl, the pressure of MgCl2 is increased, which agrees well with recently reported experiments. From these results, it is concluded that MgCl2 is the key molecule which plays the most important role for Mg-doping in fabricating p-type GaN using HVPE with MgO.

    DOI: 10.35848/1347-4065/aba0d5

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  82. Growth of high-quality GaN by halogen-free vapor phase epitaxy

    Kimura T., Kataoka K., Uedono A., Amano H., Nakamura D.

    Applied Physics Express   13 巻 ( 8 ) 頁: 085509   2020年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    We report the electrical and optical properties of gallium nitride grown by halogen-free vapor phase epitaxy (HF-VPE). The electron mobility of the HF-VPE-GaN layers was found to be comparable to or better than the GaN layers obtained using MOCVD. The positron annihilation spectroscopy analyses revealed that the density of the electroneutral or negatively charged vacancy-type defects in the HF-VPE-GaN layers was below the detection limit (≤1015 cm-3), equivalent to that of a defect-free hydride vapor phase epitaxy (HVPE)-GaN reference sample. Our study shows that the HF-VPE technique can be employed to achieve high-quality and cost-effective bulk crystal and epitaxial layer growth for GaN devices.

    DOI: 10.35848/1882-0786/aba494

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  83. Thermodynamic analysis of the gas phase reaction of Mg-doped GaN growth by HVPE using MgO

    Kimura Tomoya, Ohnishi Kazuki, Amano Yuki, Fujimoto Naoki, Araidai Masaaki, Nitta Shugo, Honda Yoshio, Amano Hiroshi, Kangawa Yoshihiro, Shiraishi Kenji

    JAPANESE JOURNAL OF APPLIED PHYSICS   59 巻 ( 8 )   2020年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  84. Growth of high-quality GaN by halogen-free vapor phase epitaxy

    Kimura Taishi, Kataoka Keita, Uedono Akira, Amano Hiroshi, Nakamura Daisuke

    APPLIED PHYSICS EXPRESS   13 巻 ( 8 )   2020年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  85. Pulsed-flow growth of polar, semipolar and nonpolar AlGaN

    Dinh Duc V, Hu Nan, Honda Yoshio, Amano Hiroshi, Pristovsek Markus

    JOURNAL OF MATERIALS CHEMISTRY C   8 巻 ( 25 ) 頁: 8668 - 8675   2020年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Materials Chemistry C  

    The impacts of pulsed-flow growth on aluminium incorporation in polar (0001), semipolar (1013) and (1122), as well as nonpolar (1010) AlGaN layers have been investigated. The layers were grown simultaneously on differently oriented AlN/sapphire templates by metal-organic vapour phase epitaxy. The AlN mole fraction (0 < xAlN ≤ 0.85) of the layers was varied by simply changing the supply time of the aluminium precursor while keeping nitrogen and gallium precursors constant. Phase separation has been observed for the (0001) and (1122) layers by X-ray diffraction, and is attributed to their different surface reconstructions during growth. In contrast, no phase separation has been observed for the (1010) and (1013) layers, attributed to their stable surfaces during growth. The AlN mole fraction of the differently oriented layers generally follows the order: (1122) < (0001) < (1013) ≤ (1010), attributed to their different surface dangling-bond densities. By means of room-temperature photoluminescence measurements, high carbon-incorporation has quantitatively been found in all the layers. This journal is

    DOI: 10.1039/d0tc01369b

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  86. Screw dislocation that converts p-type GaN to n-type: Microscopic study on Mg condensation and leakage current in p-n diodes

    T. Nakano, Y. Harashima, K. Chokawa, K. Shiraishi, A. Oshiyama, Y. Kangawa, S. Usami, N. Mayama, K. Toda, A. Tanaka, Y. Honda, H. Amano

    Applied Physics Letters   117 巻 ( 1 ) 頁: 012105   2020年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/5.0010664

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  87. Change of high-voltage conduction mechanism in vertical GaN-on-GaN Schottky diodes at elevated temperatures

    Sandupatla A., Arulkumaran S., Ng G.I., Ranjan K., Deki M., Nitta S., Honda Y., Amano H.

    Applied Physics Express   13 巻 ( 7 ) 頁: 074001   2020年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Current-voltage-temperature characteristics (0 °C to 150 °C) of SBDs on highly compensated 15 μm and 30 μm n-type GaN drift layer were measured for voltages up to-300 V and up to-800 V, respectively. When the temperature is between 75 °C and 100 °C, both SBDs exhibited a similar change in conduction mechanism from thermionic field emission (TFE) to thermionic emission (TE) due to the activation of N-vacancies (VN) (Ea =-1.67 ± 0.02 eV). However, at high voltages when the temperature is >100 °C, the conduction mechanism changes from TE to TFE due to the de-trapping of electrons from activated carbon-traps (Ea = +0.69 eV) in the grown drift layers.

    DOI: 10.35848/1882-0786/ab93a0

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  88. Change of high-voltage conduction mechanism in vertical GaN-on-GaN Schottky diodes at elevated temperatures

    Sandupatla Abhinay, Arulkumaran Subramaniam, Ng Geok Ing, Ranjan Kumud, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   13 巻 ( 7 )   2020年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  89. Effect of Annealing on the Electrical and Optical Properties of MgZnO Films Deposited by Radio Frequency Magnetron Sputtering

    Kushimoto Maki, Sakai Tadayoshi, Ueoka Yoshihiro, Tomai Shigekazu, Katsumata Satoshi, Deki Manato, Honda Yoshio, Amano Hiroshi

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   217 巻 ( 14 ) 頁: 1900955   2020年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (A) Applications and Materials Science  

    The properties of phase-separated MgZnO induced by heat treatment are investigated, because the electrical conductivity of MgZnO deposited by sputtering can be improved by heat treatment. The absorption edge shows a red shift, but the transmittance in the ultraviolet (UV)-C region increases after heat treatment. This is due to the formation of wurtzite (WZ) MgZnO with a high Zn content and a rock salt (RS) structure with a low Zn content induced by phase separation. This suggests that the current path is formed by the WZ crystals with low resistivity, and the transmittance in the UV region is increased by the RS crystals with high transmittance. It is confirmed that the RS structure is partially mixed with the WZ crystal in the in-plane direction. In contrast, different distributions of crystals are observed in the stacking direction. A WZ structure is formed after RS-MgZnO is formed on the substrate interface. It is found that Mg is incorporated into the RS structure by heat treatment, and Mg-rich MgZnO is formed.

    DOI: 10.1002/pssa.201900955

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  90. Lattice bow in thick, homoepitaxial GaN layers for vertical power devices

    Liu Q., Fujimoto N., Shen J., Nitta S., Tanaka A., Honda Y., Sitar Z., Boćkowski M., Kumagai Y., Amano H.

    Journal of Crystal Growth   539 巻   頁: 125643   2020年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Crystal Growth  

    Lattice bow generated by 40 µm thick HVPE homoepitaxial layers on commercial free-standing, ammonothermal and HVPE GaN wafers was studied. While a change in lattice bow was measured for all wafers, the additional bow on the ammonothermal GaN wafers was minimal. The main driving force for the observed increase in the lattice bow for HVPE wafers was related to stress in the films generated by the elongation of dislocations via climb and generation of new dislocations at the homoepitaxial interface. Lattice bow is a crucial wafer parameter as it determines the variation of the offcut across the surface. If an offcut variation of 0.1° is allowed for desired control surface morphology, composition of alloys, and uniformity of doping on this surface, the measured bow on the two HVPE GaN wafers and one ammonothermal GaN wafer limits their uniformity-diameter to ~0.5″, 1″ and >4″, respectively.

    DOI: 10.1016/j.jcrysgro.2020.125643

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  91. Halide vapor phase epitaxy of p-Type Mg-doped GaN utilizing MgO

    Ohnishi K., Amano Y., Fujimoto N., Nitta S., Honda Y., Amano H.

    Applied Physics Express   13 巻 ( 6 ) 頁: 016007   2020年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Halide vapor phase epitaxy of p-Type GaN:Mg films was realized by using solid MgO as the Mg source. The Mg concentration was controlled by supplying HCl gas in a MgO source zone. Mg-related photoluminescence peaks were observed at around 3.3 and 2.9 eV. For a sample with a Mg concentration of 2.8 × 1019 cm-3, the Hall-effect measurement showed p-Type conduction with a hole concentration and a hole mobility of 1.3 × 1017 cm-3 and 9.1 cm2 V-1 s-1, respectively, at room temperature. The Mg acceptor level was 232 15 meV, which is in good agreement with the previous report.

    DOI: 10.35848/1882-0786/ab9166

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  92. Halide vapor phase epitaxy of p-type Mg-doped GaN utilizing MgO

    Ohnishi Kazuki, Amano Yuki, Fujimoto Naoki, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   13 巻 ( 6 )   2020年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  93. Oxygen Incorporation Kinetics in Vicinal m(10-10) Gallium Nitride Growth by Metal-Organic Vapor Phase Epitaxy

    Yosho Daichi, Shintaku Fumiya, Inatomi Yuya, Kangawa Yoshihiro, Iwata Jun-Ichi, Oshiyama Atsushi, Shiraishi Kenji, Tanaka Atsushi, Amano Hiroshi

    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS   14 巻 ( 6 ) 頁: 2000142   2020年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi - Rapid Research Letters  

    The oxygen incorporation kinetics of vicinal m(10−10) gallium nitride (GaN) growth during metal-organic vapor phase epitaxy is clarified using a diffusion equation-based approach that incorporates diffusion potentials obtained by large-scale density functional theory (DFT) calculations. A diffusion model based on the Burton, Cabrera and Frank (BCF) theory is proposed, and then, the oxygen concentration in the epitaxial films is calculated quantitatively. The calculation results agree with the experimental tendency that the oxygen concentration in the −c 5° off m-GaN epilayers is lower than that in the +c 5° off m-GaN epilayers. Then, the off-angle dependence of oxygen incorporation in vicinal m-GaN growth is predicted.

    DOI: 10.1002/pssr.202000142

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  94. Vertical GaN-on-GaN Schottky Diodes as α-Particle Radiation Sensors.

      11 巻 ( 5 ) 頁: 519   2020年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3390/mi11050519

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    PubMed

  95. Improving the Leakage Characteristics and Efficiency of GaN-based Micro-Light-Emitting Diode with Optimized Passivation

    Lee Hoon, Lee Jung-Hoon, Park Jin-Seong, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 5 ) 頁: 055001   2020年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    We investigated the effect of atomic layer deposition (ALD) Al2O3 (50 nm)/plasma-enhanced chemical vapour deposition (PECVD) SiO2 (250 nm) and PECVD SiO2 (300 nm) passivation layers on the leakage current and efficiency of InGaN-based micro-LEDs with different sizes. Regardless of passivation layers, the leakage current increased with decreasing LED size and increasing reverse bias. Emission microscopy examination showed that with increasing reverse bias, the number of defect-related emission spots and their intensities increased. For the micro-LEDs <50 μm, the emission spots were mainly located at the sidewall regions. Above-10 V, the single PECVD SiO2 passivation layer gave higher leakage current than the double ALD-Al2O3/PECVD-SiO2 layer. The micro-LEDs with the single passivation layer gave the ideality factors of about 2.0, while that with the double layer exhibited values smaller than 2.0. The micro-LEDs with the double passivation layer exhibited external quantum efficiency peaks at lower current density compared to those with the single layer. It was shown that smaller micro-LEDs were more sensitively dependent on the types of the passivation layers. These results exhibit that the ALD-Al2O3/PECVD-SiO2 passivation layer is more effective in suppressing the sidewall damage-induced current than the PECVD-SiO2 layer.

    DOI: 10.1149/2162-8777/ab915d

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  96. Impact of high-Temperature implantation of Mg ions into GaN

    Takahashi M., Tanaka A., Ando Y., Watanabe H., Deki M., Kushimoto M., Nitta S., Honda Y., Shima K., Kojima K., Chichibu S.F., Amano H.

    Japanese Journal of Applied Physics   59 巻 ( 5 ) 頁: 056502   2020年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    Magnesium (Mg) ion implantation into gallium nitride (GaN) at 1000 °C is proposed. Since ion implantation and annealing occur simultaneously in high-Temperature implantation, it is considered that Mg ions can be introduced at an appropriate position upon their implantation. GaN vertical diodes implanted with Mg ions were fabricated and current-voltage measurements were performed. As a result, clear rectifying properties were confirmed in a sample that was implanted with Mg ions at 1000 °C and annealed after implantation. However, the sample subjected to Mg ion implantation at RT and annealed after implantation showed no clear rectification. These results show that high-Temperature implantation of Mg ions at 1000 °C reduces Mg ion implantation-induced damage and simultaneously activates Mg ions upon their implantation.

    DOI: 10.35848/1347-4065/ab8b3d

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  97. Computational study of oxygen stability in vicinal m(10-10)-GaN growth by MOVPE

    Shintaku F., Yosho D., Kangawa Y., Iwata J.I., Oshiyama A., Shiraishi K., Tanaka A., Amano H.

    Applied Physics Express   13 巻 ( 5 ) 頁: 055507   2020年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Using density functional calculations, we clarify the oxygen incorporation mechanism in vicinal m-GaN growth by metal-organic vapor-phase epitaxy. We first identify reconstructed structures of 5° off m-GaN toward the ±c directions. Next, we explore preferable sites for oxygen substitution near step edges. We find that oxygen prefers the lower nitrogen site of the step edge on the +c 5° off m-GaN substrate compared with that on the-c 5° off m-GaN substrate. This tendency agrees with recent experimental findings that the oxygen concentration in-c 5° off m-GaN epilayers is lower than that in +c 5° off m-GaN epilayers.

    DOI: 10.35848/1882-0786/ab8723

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  98. Impact of high-temperature implantation of Mg ions into GaN

    Takahashi Masahiro, Tanaka Atsushi, Ando Yuto, Watanabe Hirotaka, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Shima Kohei, Kojima Kazunobu, Chichibu Shigefusa F., Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   59 巻 ( 5 )   2020年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  99. Computational study of oxygen stability in vicinal m(10-10)-GaN growth by MOVPE

    Shintaku Fumiya, Yosho Daichi, Kangawa Yoshihiro, Iwata Jun-Ichi, Oshiyama Atsushi, Shiraishi Kenji, Tanaka Atsushi, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   13 巻 ( 5 )   2020年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  100. Improved Leakage and Output Characteristics of Pixelated LED Array for Headlight application

    Lee Sang-Youl, Kang Kiman, Lee Eunduk, Jo Yoomin, Kim Doyub, Oh Jeong-Tak, Jeong Hwan-Hee, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 4 ) 頁: 045011   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2162-8777/ab8b6f

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  101. Experimental observation of high intrinsic thermal conductivity of AlN

    Cheng Zhe, Koh Yee Rui, Mamun Abdullah, Shi Jingjing, Bai Tingyu, Huynh Kenny, Yates Luke, Liu Zeyu, Li Ruiyang, Lee Eungkyu, Liao Michael E., Wang Yekan, Yu Hsuan Ming, Kushimoto Maki, Luo Tengfei, Goorsky Mark S., Hopkins Patrick E., Amano Hiroshi, Khan Asif, Graham Samuel

    PHYSICAL REVIEW MATERIALS   4 巻 ( 4 ) 頁: 044602   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevMaterials.4.044602

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  102. Tungsten carbide layers deposited on graphite substrates via a wet powder process as anti-parasitic-reaction coatings for reactor components in GaN growth

    Nakamura Daisuke, Kimura Taishi, Itoh Kenji, Fujimoto Naoki, Nitta Shugo, Amano Hiroshi

    CRYSTENGCOMM   22 巻 ( 15 ) 頁: 2632 - 2641   2020年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1039/c9ce01971e

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  103. Improved Light Output of AlGaInP-Based Micro-Light Emitting Diode Using Distributed Bragg Reflector

    Lee Sang-Youl, Moon Ji Hyung, Moon Yong-Tae, Kim Chung Song, Park Sunwoo, Oh Jeong-Tak, Jeong Hwan-Hee, Seong Tae-Yeon, Amano Hiroshi

    IEEE PHOTONICS TECHNOLOGY LETTERS   32 巻 ( 7 ) 頁: 438 - 441   2020年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Photonics Technology Letters  

    We investigated how the performance and reliability of AlGaInP-based red (620 nm) micro-light-emitting diodes (micro-LEDs) (25×17 μ m2) were influenced by the use of n-AlInP ohmic layer and distributed Bragg reflector (DBR). The AlGaAs-based DBR showed reflectivity of 94.9% at 622 nm with a 14 nm-stopband width. The micro-LEDs with n-GaAs gave slightly lower forward voltages by 0.013 - 0.021 V than those with n-Al0.5In0.5P/ n-Al0.6Ga0.4As and nAl0.5In0.5P/DBR. However, the micro-LEDs with n-Al0.5In0.5P/ n-Al0.6Ga0.4As and n-Al0.5In0.5P/DBR gave 61% and 125% higher light output power at 20μ A compared with that with n-GaAs. It was shown that after annealing at 120 °C for 2,000 h, the forward voltage and the light output power at 4.7 A/cm2 of the micro-LEDs with n-Al0.5In0.5P/DBR were degraded by 0.09% and 6.33%, respectively, with reference to those before annealing.

    DOI: 10.1109/LPT.2020.2977376

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  104. Scalable fabrication of GaN on amorphous substrates via MOCVD on highly oriented silicon seed layers

    Hainey Mel Jr., Robin Yoann, Avit Geoffrey, Amano Hiroshi, Usami Noritaka

    JOURNAL OF CRYSTAL GROWTH   535 巻   頁: 125522   2020年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Crystal Growth  

    The integration of gallium nitride with low-cost, transparent substrates such as glass and crystallographically incompatible substrates such as Si(0 0 1) has been long desired for III-N electronics. Here the authors demonstrate how GaN growth on uniformly 〈1 1 1〉 oriented silicon seed layers fabricated by aluminum-induced crystallization provide a straightforward method for realizing large area GaN growth on these substrate by adopting well-developed GaN on Si(1 1 1) growth processes. Critical factors for promoting high quality GaN growth are identified, and remaining steps necessary for realizing GaN devices are discussed.

    DOI: 10.1016/j.jcrysgro.2020.125522

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  105. Demonstration of Observation of Dislocations in GaN by Novel Birefringence Method

    Tanaka Atsushi, Inotsume Syo, Harada Shunta, Hanada Kenji, Honda Yoshio, Ujihara Toru, Amano Hiroshi

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   257 巻 ( 4 ) 頁: 1900553   2020年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (B) Basic Research  

    Herein, a newly developed birefringence microscope is used to observe dislocations in gallium nitride (GaN) substrates. The comparison results of the observation method using this microscope with other observation methods, such as X-ray topography and Raman microscopy, confirms that dislocations in a GaN substrate can be detected with a birefringence microscope. In addition, the observation can be carried out as easily as with an optical microscope. It is also found that under certain observation conditions, the direction of the edge component of dislocations can be determined.

    DOI: 10.1002/pssb.201900553

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  106. On-wafer fabrication of etched-mirror UV-C laser diodes with the ALD-deposited DBR

    Sakai Tadayoshi, Kushimoto Maki, Zhang Ziyi, Sugiyama Naoharu, Schowalter Leo J., Honda Yoshio, Sasaoka Chiaki, Amano Hiroshi

    APPLIED PHYSICS LETTERS   116 巻 ( 12 ) 頁: 122101   2020年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    We have demonstrated an on-wafer fabrication process for AlGaN-based UV-C laser diodes (LDs) with etched mirrors and have achieved lasing for 100 ns pulsed current injection at room temperature. A combined process of dry and wet etching was employed to achieve smooth and vertical AlGaN (1 1 &macr;00) facets. These etched facets were then uniformly coated with a distributed Bragg reflector by atomic layer deposition. A remarkable reduction of the lasing threshold current density to 19.6 kA / cm 2 was obtained owing to the high reflectivity of the etched and coated mirror facets. The entire laser diode fabrication process was carried out on a whole 2-in. wafer. We propose this mirror fabrication process as a viable low-cost AlGaN-based UV-C LD production method that is also compatible with highly integrated optoelectronics based on AlN substrates.

    DOI: 10.1063/1.5145017

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  107. Effects of Ultraviolet Wavelength and Ambient Temperature on Reliability of Silicones in InAlGaN-Based Light-Emitting-Diode Package

    Kim Ho-Young, Lee Jong-Woo, Jun Duk-Jin, Song Sung-Joo, Oh Jeong-Tak, Jeong Hwan-Hee, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 3 ) 頁: 035005   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2162-8777/ab7c40

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  108. Visualization of different carrier concentrations in n-type-GaN semiconductors by phase-shifting electron holography with multiple electron biprisms.

    Yamamoto K, Nakano K, Tanaka A, Honda Y, Ando Y, Ogura M, Matsumoto M, Anada S, Ishikawa Y, Amano H, Hirayama T

    Microscopy (Oxford, England)   69 巻 ( 1 ) 頁: 1-10   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1093/jmicro/dfz037

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    PubMed

  109. Using SiO2-Based Distributed Bragg Reflector to Improve the Performance of AlGaInP-Based Red Micro-Light Emitting Diode

    Lee Sang-Youl, Moon Ji Hyung, Moon Yong-Tae, Choi Byoungjun, Oh Jeong-Tak, Jeong Hwan-Hee, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 3 ) 頁: 036002   2020年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2162-8777/ab74c3

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  110. Using SiO<inf>2</inf>-based distributed Bragg reflector to improve the performance of AlGaInP-based red micro-light emitting diode

    Lee S.Y., Moon J.H., Moon Y.T., Choi B., Oh J.T., Jeong H.H., Seong T.Y., Amano H.

    ECS Journal of Solid State Science and Technology   9 巻 ( 3 )   2020年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    We have investigated how different types of the reflectors affected the optical and electrical performance of AlGaInP-based micro-LEDs. Simulations showed that the AlGaAs-based epitaxial distributed Bragg reflector (DBR) had a stopband at the 610–624 nm region with reflectivity of 90%, the SiO2/TiO2 dielectric DBR gave a stopband at the 580–770 nm range with a maximum reflectivity of 99%, and the ITO/Ag metal reflector exhibited reflectivity of 90% across the 400–800 nm region. All micro-LEDs gave forward voltages of 1.895–1.960 V at 20 μA. The micro-LEDs with the dielectric DBR and metal reflector yielded 31% and 13% higher light output at 20 μA than that with the epitaxial DBR, respectively. All of the micro-LEDs contained a shoulder peak at approximately 615 nm in their electroluminescence spectra. Ray-tracing simulations exhibited that the micro-LEDs with the dielectric DBR and metal reflector produced 26% and 22% higher total light output power than the one with the epitaxial DBR, respectively. It was also shown that for the micro-LEDs with the metal reflector, some of the micro-LEDs were detached from the metal reflectors due to the interfacial voids induced as a result of agglomeration of Ag layer during fabrication process.

    DOI: 10.1149/2162-8777/ab74c3/pdf

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  111. Optimization of InGaN thickness for high-quantum-efficiency Cs/O-activated InGaN photocathode

    Sato Daiki, Honda Anna, Koizumi Atsushi, Nishitani Tomohiro, Honda Yoshio, Amano Hiroshi

    MICROELECTRONIC ENGINEERING   223 巻   頁: 111229   2020年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Microelectronic Engineering  

    The quantum efficiency (QE) of an InGaN photocathode as a function of InGaN layer thickness (240, 100, and 70 nm) was investigated. To activate the sample surface, Cs and O were deposited on the surface in an ultrahigh–vacuum chamber. The QE for different optical power densities was measured by irradiating excitation light from the front and back sides of each sample. The QEs for InGaN layer thickness of 240, 100, and 70 nm with back-side irradiation were 0.9, 9.8, and 7.5%, respectively. For the thicknesses of 70 and 100 nm, the QEs were higher for back-side irradiation than for front-side irradiation, whereas for the thickness of 240 nm, the QE was higher for front-side irradiation. The InGaN layer thickness dependence of the QEs for back- and front-side irradiations was calculated using a continuous equation considering processes such as excitation, diffusion, recombination, and escape of electrons from the surface of the photocathode. The tendency of the experimental results, where QE was maximum at 100–120 nm, corresponded to that of the calculated results.

    DOI: 10.1016/j.mee.2020.111229

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  112. Effect of unevenly-distributed V pits on the optical and electrical characteristics of green micro-light emitting diode

    Lee Da-Hoon, Kang Daesung, Seong Tae-Yeon, Kneissl Michael, Amano Hiroshi

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   53 巻 ( 4 ) 頁: 045106   2020年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6463/ab52d0

    Web of Science

  113. Oblique-Angle Deposited SiO2/Al Omnidirectional Reflector for Enhancing the Performance of AlGaN-Based Ultraviolet Light-Emitting Diod

    Jeongwon Lee, Tae-Yeon Seong, Hiroshi Amano

    ECS Journal of Solid State Science and Technology   9 巻 ( 2 )   2020年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2162-8777/ab709a

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  114. Oblique-Angle Deposited SiO2/Al Omnidirectional Reflector for Enhancing the Performance of AlGaN-Based Ultraviolet Light-Emitting Diode

    Jeongwon Lee, Tae-Yeon Seong, Hiroshi Amano

    ECS Journal of Solid State Science and Technology   9 巻 ( 2 ) 頁: 026005   2020年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2162-8777/ab709a

  115. Heavy Mg Doping to Form Reliable Rh Reflective Ohmic Contact for 278 nm Deep Ultraviolet AlGaN-Based Light-Emitting Diodes

    Lee Sang-Youl, Han Dae-Seob, Lee Yong-Gyeong, Choi Kwang-Ki, Oh Jeong-Tak, Jeong Hwan-Hee, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 6 ) 頁: 065016   2020年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2162-8777/aba914

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  116. Improved breakdown voltage in vertical GaN Schottky barrier diodes on free-standing GaN with Mg-compensated drift layer

    Abhinay S., Arulkumaran S., Ng G. I., Ranjan K., Deki M., Nitta S., Honda Y., Amano H.

    JAPANESE JOURNAL OF APPLIED PHYSICS   59 巻 ( 1 ) 頁: 010906   2020年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    Vertical Schottky barrier diodes (SBD) were fabricated on 1a 5 μm thick GaN drift layer (DL) with and without Mg-compensation grown by metal organic chemical vapour deposition on free-standing hydride vapour phase epitaxy grown substrate. The SBDs with Mg-compensated DL exhibited ∼3.4 × higher breakdown voltage (V bd) than the SBDs with conventional DL. The activation energy of 0.43 eV from the SBD with Mg-compensated DL can be correlated to the presence of Mg. The reverse current conduction mechanism of SBDs with Mg-compensated DL and conventional DL was dominated by thermionic field emission (TFE) and barrier modified TFE, respectively.

    DOI: 10.7567/1347-4065/ab65cd

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  117. Recovery of quantum efficiency on Cs/O-activated GaN and GaAs photocathodes by thermal annealing in vacuum

    Daiki Sato, Tomohiro Nishitani, Yoshio Honda, Hiroshi Amano

    Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics   38 巻 ( 1 ) 頁: 012603   2020年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1116/1.5120417

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  118. Scalable synthesis of multilayer h-BN on AlN by metalorganic vapor phase epitaxy: nucleation and growth mechanism

    Yang Xu, Nitta Shugo, Pristovsek Markus, Liu Yuhuai, Liao Yaqiang, Kushimoto Maki, Honda Yoshio, Amano Hiroshi

    2D MATERIALS   7 巻 ( 1 ) 頁: 015004   2020年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:2D Materials  

    We studied the nucleation and growth of hexagonal BN (h-BN) on AlN template on c-plane sapphire by metalorganic vapor phase epitaxy as functions of growth temperature, deposition time, and triethylboron (TEB) partial pressure. A lateral growth rate of about 25 nm min-1 for h-BN nuclei was obtained by atomic force microscopy and a nucleation activation energy of 2.1 eV was extracted from the temperature dependence of the nucleation density. A large TEB flow rate strongly enhances the formation of h-BN nuclei. At a reduced TEB flow rate, we observed a significantly decreased nuclei density and a delay in nucleation due to TEB desorption. By fine tuning the growth parameters, single-crystalline multilayer h-BN was successfully formed on AlN surface, as confirmed by x-ray diffraction and transmission electron microscopy (TEM). The epitaxial relationship between h-BN and AlN was [0 0 0 1]h-BN || [0 0 0 1]AlN and [1 0 -1 0]h-BN || [1 1 -2 0]AlN from TEM and electron backscatter diffraction measurements. In addition, TEM showed that the initial h-BN layers are not parallel and tend to form half-domes. On those half-domes (cap-shaped-like) a 2D lateral growth sets on, resulting in a well-oriented 2D multilayer observed in TEM. Thus, the surface topography further develops to form a relatively flat surface without wrinkles and finally a typical hexagon-like wrinkled surface at thicker h-BN layers. Particularly, the small h-BN nuclei have dangling bonds at their periphery that can interact with the substrate, forming actual bonds with AlN. Hence the choice on the substrate is important, despite the basal planes of multilayer h-BN are bonded by a weak van der Waals force.

    DOI: 10.1088/2053-1583/ab46e6

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  119. Analysis of trimethylgallium decomposition by high-resolution mass spectrometry

    Zheng Ye, Shugo Nitta, Yoshio Honda, Markus Pristovsek, Hiroshi Amano

    Japanese Journal of Applied Physics   59 巻 ( 2 ) 頁: 025511   2020年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.35848/1347-4065/ab6fb0

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  120. Preface - JSS Focus Issue on Recent Advances in Wide Bandgap III-Nitride Devices and Solid State Lighting: A Tribute to Isamu Akasaki

    Ren F., Mishra K.C., Amano H., Collins J., Han J., Im W.B., Kneissl M., Seong T.Y., Setlur A., Suski T., Zych E.

    ECS Journal of Solid State Science and Technology   9 巻 ( 1 ) 頁: 010001   2020年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    DOI: 10.1149/2.0452001JSS

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  121. Indium incorporation and optical properties of polar, semipolar and nonpolar InAlN

    Duc V Dinh, Nan Hu, Yoshio Honda, Hiroshi Amano, Markus Pristovsek

    Semiconductor Science and Technology   35 巻 ( 3 ) 頁: 035004   2020年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6641/ab63f1

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  122. Damage-Free Plasma Etching to Enhance Performance of AlGaInP-Based Micro-Light Emitting Diode

    Lee Sang-Youl, Lee Eunduk, Moon Ji-Hyung, Choi Byoungjun, Oh Jeong-Tak, Jeong Hwan-Hee, Seong Tae-Yeon, Amano Hiroshi

    IEEE PHOTONICS TECHNOLOGY LETTERS   32 巻 ( 17 ) 頁: 1041 - 1044   2020年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Photonics Technology Letters  

    We investigated the effect of plasma-etching on the electrical and optical performance of lateral AlGaInP-based red micro-LEDs as a function of etching time, where plasma-etched Ag particles were used as masks. For the sample etched for 12 s, around 33% of the sample surface were randomly etched, whereas for the sample etched for 24 s, nearly 60% were randomly etched with additional nanoscale hillocks. Regardless of etching times, all samples exhibited similar forward voltages of 1.944-1.929 V at $20~\mu \text{A}$ and reverse leakage currents of $1\times 10^{-8}$ A at -10 V. The micro-LEDs fabricated with 12 s-etched and 24 s-etched $p$ -GaP gave 26.2% and 42.3% higher light output powers at $20~\mu \text{A}$ , respectively, than the one with unetched $p$ -GaP. The $S$ parameter decreased with increasing forward current and etching time. The electroluminescence (EL) peak intensities of the micro-LEDs were consistent with their light output performance and included shoulder peaks at 612 nm. Emission images showed that the micro-LEDs with the 24 s-etched $p$ -GaP revealed the most intense and uniform emission area among the three samples.

    DOI: 10.1109/LPT.2020.3010820

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  123. マクロステップを持つ<i>c</i>面AlN/サファイアテンプレート上に成長させたAlGaN量子井戸の物性評価

    小島 一信, 長澤 陽祐, 平野 光, 一本松 正道, 杉江 隆一, 本田 善央, 天野 浩, 赤﨑 勇, 秩父 重英

    日本結晶成長学会誌   47 巻 ( 3 ) 頁: n/a   2020年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:日本結晶成長学会  

    <p>  The microscopic structural and optical characteristics of AlGaN light-emitting diodes (LEDs) fabricated on the AlN templates with dense macrosteps are shown to clarify the origin of their high internal quantum efficiency of radiation (IQE). The cross-sectional transmission electron microscopy observations under the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy revealed that the AlGaN cladding layer under the AlGaN quantum well (QW) layer had a microscopic compositional modulation, which originates from the macrosteps at the AlN template surface. Moreover, Ga-rich portions in the cladding layer behaved as current micropaths, and the micropaths are connected with the carrier localization structure formed in QWs. The in-plane cathodoluminescence (CL) spectroscopy showed a significant inhomogeneity of the CL characteristics. The gentle slopes at the sample surface showed brighter emissions with a lower peak photon energy, confirming the carrier localization. This carrier localization structure in the QWs combined with the current micropaths in the cladding layer can increase the IQE as well as external quantum efficiency of the AlGaN LEDs.</p>

    DOI: 10.19009/jjacg.47-3-04

    CiNii Research

  124. Role of defects in the mid-term degradation of UV-B LEDs investigated by optical and DLTS measurements

    Piva F., De Santi C., Deki M., Kushimoto M., Amano H., Tomozawa H., Shibata N., Meneghesso G., Zanoni E., Meneghini M.

    GALLIUM NITRIDE MATERIALS AND DEVICES XV   11280 巻   頁: 1128015   2020年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering  

    AlGaN-based UltraViolet Light Emitting Diodes (UV LEDs) are promising devices for replacing the conventional UV lamps, which contain toxic substances like mercury, in order to have smaller devices, lower operating voltage and the possibility of tuning the emission wavelength by changing the Al and Ga content in the alloy. However, UV-LEDs may suffer from a relatively fast degradation of electrical and optical characteristics, that can be due to the generation of defects that increase the Shockley-Read-Hall (SRH) recombination components. The aim of this paper is to study the behavior of UV-B LEDs submitted to a constant current stress, through electrical, optical and spectral characterization, and capacitance deep-level transient spectroscopy (C-DLTS). The results of this analysis demonstrate that UV-B LEDs show a decrease in the driving voltage, probably correlated with the increased activation of the Mg dopant, and an increase in subthreshold forward current, ascribed to the generation of mid-gap defects caused by the stress. We also found a strong optical degradation at low current levels, that indicates the increase in SRH recombination, probably due to the increased density of mid-gap defects. To investigate on the origin of the defects, we carried out C-DLTS measurements; the results indicate the presence of Mg-related defects and/or intrinsic defects related to the GaN growth. Moreover, after stress we notice the appearance of a peak that is strictly related to the increase of mid-gap defects generated during the stress.

    DOI: 10.1117/12.2544704

    Web of Science

    Scopus

  125. Low leakage Mg-compensated GaN Schottky diodes on free-standing GaN substrate for high energy alpha-particle detection

    Sandupatia A., Arulkurnaran S., Ranjan K., Ng G. I, Murumu P. P., Kennedy J., Deki M., Nitta S., Honda Y., Amano H.

    2020 IEEE ELECTRON DEVICES TECHNOLOGY AND MANUFACTURING CONFERENCE (EDTM 2020)     2020年

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    掲載種別:研究論文(学術雑誌)  

    Web of Science

  126. Dielectric Ruduced Surface Field Effect on Vertical GaN-on-GaN Nanowire Schottky Barrier Diodes

    Liao Yaqiang, Chen Tao, Wang Jia, Ando Yuto, Yang Xu, Watanabe Hirotaka, Hirotani Jun, Kushimoto Maki, Deki Manato, Tanaka Atsushi, Nitta Shugo, Honda Yoshio, Chen Kevin J., Amano Hiroshi

    PROCEEDINGS OF THE 2020 32ND INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES AND ICS (ISPSD 2020)     頁: 349 - 352   2020年

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    掲載種別:研究論文(学術雑誌)  

    Web of Science

  127. GaN基板向けレーザスライシング技術の開発

    河口 大祐, 田中 敦之, 油井 俊樹, 伊ヶ崎 泰則, 和仁 陽太郎, 天野 浩

    年次大会   2020 巻 ( 0 ) 頁: S16306   2020年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 日本機械学会  

    DOI: 10.1299/jsmemecj.2020.s16306

    CiNii Research

  128. Improvement of The Light Output of Blue InGaN-Based Light Emitting Diodes by Using a Buried Stripe -Type n-Contact and Reflective Bonding Pad

    Kim Jong-Ho, Lee Yong Won, Im Hyeong-Seop, Oh Chan-Hyoung, Shim Jong-In, Kang Daesung, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 1 ) 頁: 015021   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    To enhance the light output of blue InGaN-based light emitting diodes (LEDs), a buried stripe-type n-electrode, expanded stripe-type p-electrode, and reflective p-bonding pad were employed. Flip-chip (FC) LEDs with the expanded p-electrode gave forward voltages of 2.99-3.11 V at 100 mA and series resistances of 3.28-3.94 Ω. The expanded p-electrode FCLED fabricated with 375 nm-thick window and TiO2 adhesion layers produced 22.7% higher light output at 21 A/cm2 than conventional FCLEDs. The expanded p-electrode FCLEDs revealed better current spreading efficiency than the c-FCLED, indicating the importance of the use of an optimised window and TiO2 adhesion layers.

    DOI: 10.1149/2.0462001JSS

    Web of Science

    Scopus

  129. Two-dimensional analysis of the nonuniform quantum yields of multiple quantum wells for AlGaN-based deep-ultraviolet LEDs grown on AlN templates with dense macrosteps using cathodoluminescence spectroscopy

    Nagasawa Y., Sugie R., Kojima K., Hirano A., Ippommatsu M., Honda Y., Amano H., Akasaki I., Chichibu S.F.

    Journal of Applied Physics   126 巻 ( 21 ) 頁: 215703   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    AlGaN-based deep-ultraviolet light-emitting diodes (LEDs) incorporating uneven multiple quantum wells (MQWs) with inclined and terrace zones, which were fabricated on an AlN template with dense macrosteps, have exhibited a high internal quantum efficiency (IQE). To investigate the microscopic structure of uneven MQWs, cathodoluminescence (CL) mapping characterization was carried out, and the maps of the CL intensity at 300 K relative to that at 38 K were obtained for uneven MQWs that targeted 265 and 285 nm LEDs. At an electron beam current of less than 1.0 nA, the signals from inclined and terrace zones of the uneven MQWs were confirmed to satisfy the nonsaturated excitation condition at 300 K. Nonradiative recombination (NR) was insufficiently frozen even at 38 K, specifically on the terraces in the 265 nm MQW, suggesting high concentrations of NR centers due to point defects (PDs). In contrast, NR in the 285 nm MQW at 38 K was closer to freeze-out. The concentration of PDs in the 285 nm MQW was likely to be lower than that in the 265 nm MQW. Finally, the ratios of the CL intensity at 300 K to those at 38 K were mapped, demonstrating an approach to creating an approximate map of IQE. The values in the CL intensity ratio maps are discussed by considering the analytical error factors. The results support the model of localized current injection through Ga-rich stripe zones in the n-AlGaN cladding layer.

    DOI: 10.1063/1.5125623

    Web of Science

    Scopus

  130. Suppression of Green Luminescence of Mg-Ion-Implanted GaN by Subsequent Implantation of Fluorine Ions at High Temperature

    Takahashi Masahiro, Tanaka Atsushi, Ando Yuto, Watanabe Hirotaka, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Shima Kohei, Kojima Kazunobu, Chichibu Shigefusa F., Chen Kevin J., Amano Hiroshi

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   257 巻   頁: 1900554   2019年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssb.201900554

    Web of Science

  131. A 271.8 nm deep-ultraviolet laser diode for room temperature operation

    Zhang Ziyi, Kushimoto Maki, Sakai Tadayoshi, Sugiyama Naoharu, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   12 巻 ( 12 ) 頁: 124003   2019年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/1882-0786/ab50e0

    Web of Science

  132. Untwinned semipolar (10(1)over-bar3) AlxGa1-xN layers grown on m-plane sapphire

    Dinh Duc V., Hu Nan, Amano Hiroshi, Honda Yoshio, Pristovsek Markus

    SEMICONDUCTOR SCIENCE AND TECHNOLOGY   34 巻 ( 12 ) 頁: 125012   2019年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6641/ab4d2c

    Web of Science

  133. Low Voltage High-Energy alpha-Particle Detectors by GaN-on-GaN Schottky Diodes with Record-High Charge Collection Efficiency

    Sandupatla Abhinay, Arulkumaran Subramaniam, Ranjan Kumud, Ng Geok Ing, Murmu Peter P., Kennedy John, Nitta Shugo, Honda Yoshio, Deki Manato, Amano Hiroshi

    SENSORS   19 巻 ( 23 ) 頁: 5107   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors (Switzerland)  

    A low voltage (–20 V) operating high-energy (5.48 MeV) α-particle detector with a high charge collection efficiency (CCE) of approximately 65% was observed from the compensated (7.7 × 1014 /cm3) metalorganic vapor phase epitaxy (MOVPE) grown 15 µm thick drift layer gallium nitride (GaN) Schottky diodes on free-standing n+-GaN substrate. The observed CCE was 30% higher than the bulk GaN (400 µm)-based Schottky barrier diodes (SBD) at –20 V. This is the first report of α–particle detection at 5.48 MeV with a high CCE at –20 V operation. In addition, the detectors also exhibited a three-times smaller variation in CCE (0.12 %/V) with a change in bias conditions from –120 V to –20 V. The dramatic reduction in CCE variation with voltage and improved CCE was a result of the reduced charge carrier density (CCD) due to the compensation by Mg in the grown drift layer (DL), which resulted in the increased depletion width (DW) of the fabricated GaN SBDs. The SBDs also reached a CCE of approximately 96.7% at –300 V.

    DOI: 10.3390/s19235107

    Web of Science

    Scopus

    PubMed

  134. Improvement in the Reliability of AlGaInP-Based Light-Emitting Diode Package Using Optimal Silicone and Leadframe Structure

    Kim Ho-Young, Lee Jong Woo, Moon Young Min, Oh Jeong Tak, Jeong Hwan-Hee, Song June-O, Seong Tae-Yeon, Kneissl Michael, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   9 巻 ( 1 ) 頁: 015014   2019年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1149/2.0332001JSS

    Web of Science

  135. Aluminium incorporation in polar, semi- and non-polar AlGaN layers: a comparative study of x-ray diffraction and optical properties

    Duc V Dinh, Hu Nan, Honda Yoshio, Amano Hiroshi, Pristovsek Markus

    SCIENTIFIC REPORTS   9 巻   頁: 15802   2019年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41598-019-52067-y

    Web of Science

  136. Hole injection mechanism in the quantum wells of blue light emitting diode with V pits for micro-display application

    Kang Daesung, Oh Jeong-Tak, Song June-O, Seong Tae-Yeon, Kneissl Michael, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   12 巻 ( 10 ) 頁: 102016   2019年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/1882-0786/ab45d1

    Web of Science

  137. V-shaped dislocations in a GaN epitaxial layer on GaN substrate

    Tanaka Atsushi, Nagamatsu Kentaro, Usami Shigeyoshi, Kushimoto Maki, Deki Manato, Nitta Shugo, Honda Yoshio, Bockowski Michal, Amano Hiroshi

    AIP ADVANCES   9 巻 ( 9 ) 頁: 095002   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5114866

    Web of Science

  138. Stability and degradation of AlGaN-based UV-B LEDs: Role of doping and semiconductor defects

    Piva F., De Santi C., Deki M., Kushimoto M., Amano H., Tomozawa H., Shibata N., Meneghesso G., Zanoni E., Meneghini M.

    MICROELECTRONICS RELIABILITY   100 巻   頁: 113418   2019年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Microelectronics Reliability  

    Within this paper, we present an extensive analysis of the degradation of UV-B light-emitting diodes (LEDs) submitted to constant current stress. The study is based on combined electrical, optical and spectral characterization, and capacitance deep-level transient spectroscopy (C-DLTS). The results of this analysis demonstrate that the decrease in the optical power during the stress is stronger at low measuring current levels, indicating that the degradation is related to the increase in Shockley-Read-Hall (SRH) recombination. The electrical characterization shows a decrease in the driving voltage, probably due to an increased activation of the Mg dopant, and an increase in the sub-threshold forward current, that suggest a generation of mid-gap states during the stress. C-DLTS measurements were carried out to study the variation in defects concentration after stress; the most relevant traps were ascribed to the presence of Mg doping and/or to intrinsic defects related to the GaN growth.

    DOI: 10.1016/j.microrel.2019.113418

    Web of Science

    Scopus

  139. Via-Hole-Type Flip-Chip Packaging to Improve the Thermal Characteristics and Reliability of Blue Light Emitting Diodes

    Kim Ho Young, Lim Chang Man, Kim Ki Seok, Oh Jeong Tak, Jeong Hwan-Hee, Song June-O, Seong Tae-Yeon, Amano Hiroshi

    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY   8 巻 ( 9 ) 頁: Q165 - Q170   2019年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Journal of Solid State Science and Technology  

    We investigated the effect of via-holes in the lead-frame on the reliability of blue flip-chip light-emitting diodes (FCLEDs). For bonding, conventional Sn-Ag(3.0%)-Cu(0.5%) solder (SAC) and Ag sintered paste were adopted. Lateral LED, conventional FCLED (c-FCLED), and via-hole FCLED gave efficacies of 218.5, 221.6 and 225 lm/W at 30 mA. The lateral LED sample (bonding material: silicone), c-FCLED sample (SAC), via-hole-type sample (Ag sinter), and via-hole-type sample (SAC) exhibited total thermal resistance of 15.24, 10.19, 8.95, and 11.79 K/W, respectively. The humidity/temperature/H2S gas reliability examinations showed that unlike the via-hole-type samples, the lumen of the c-FCLED was fallen by 15.0% after exposure for 500 h. Furthermore, the c-FCLED exhibited a 19.6% higher forward voltage than the via-hole FCLED after 1,000 thermal-cycles. SEM results showed that unlike the via-hole type FCLED, the c-FCLED underwent cracking after thermal cycle of 1000 times.

    DOI: 10.1149/2.0171909jss

    Web of Science

    Scopus

  140. Combined effects of V pits and chip size on the electrical and optical properties of green InGaN-based light-emitting diodes

    Kim Dae-Hyun, Park Young Soo, Kang Daesung, Kim Kyoung-Kook, Seong Tae-Yeon, Amano Hiroshi

    JOURNAL OF ALLOYS AND COMPOUNDS   796 巻   頁: 146-152   2019年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jallcom.2019.05.070

    Web of Science

  141. Indium Incorporation into InGaN Quantum Wells Grown on GaN Narrow Stripes

    Sarzynski Marcin, Grzanka Ewa, Grzanka Szymon, Targowski Grzegorz, Czernecki Robert, Reszka Anna, Holy Vaclav, Nitta Shugo, Liu Zhibin, Amano Hiroshi, Leszczynski Mike

    MATERIALS   12 巻 ( 16 ) 頁: 2583   2019年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3390/ma12162583

    Web of Science

  142. Influence of Temperature-Dependent Substrate Decomposition on Graphene for Separable GaN Growth

    Park Jeong-Hwan, Lee Jun-Yeob, Park Mun-Do, Min Jung-Hong, Lee Je-Sung, Yang Xu, Kang Seokjin, Kim Sang-Jo, Jeong Woo-Lim, Amano Hiroshi, Lee Dong-Seon

    ADVANCED MATERIALS INTERFACES   6 巻   頁: 1900821   2019年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/admi.201900821

    Web of Science

  143. Fabrication of a GaInN/GaInP/GaInAs/Ge four-junction solar cell using the wafer bonding technology

    Takahashi Kazuya, Shinoda Ryoji, Mitsufuji Syun, Iwaya Motoaki, Kamiyama Satoshi, Takeuchi Tetsuya, Hattori Tomokazu, Akasaki Isamu, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( 7 ) 頁: 072003   2019年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    We fabricated a GaInN/GaInP/GaInAs/Ge four-junction solar cell by wafer bonding a GaInN solar cell and a GaInP/GaInAs/Ge three-junction solar cell. We performed our wafer bonding at high pressure (500 N) and temperature (450 °C) by using p-type GaN and n-type GaAs. The open-circuit voltage (V OC), J SC, and fill factor of our four-junction solar cell under the condition of AM 1.5 G, i.e., 1 sun are 2.85 V, 0.219 mA cm-2, and 0.74, respectively. The improved V OC of our four-junction solar cells was confirmed by a series connection. The J SC is almost comparable to the theoretical value (itself based on the assumption of an ideal series junction), but the V OC is approximately 1 V less than that predicted by theory. Our research will improve the solar cell efficiency and help meet future energy needs.

    DOI: 10.7567/1347-4065/ab26ad

    Web of Science

    Scopus

  144. Origin of acceptor diffusion into silicon substrate during GaN growth by metal organic chemical vapor deposition

    Matsumoto Koji, Ono Toshiaki, Honda Yoshio, Torigoe Kazuhisa, Kushimoto Maki, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( 7 ) 頁: 075502   2019年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    This study investigated the change in carrier concentration near the surface of a silicon substrate during gallium nitride (GaN) growth with an aluminum nitride (AlN) buffer layer. It was observed that aluminum, gallium, and carbon diffused into the silicon substrate during the growth process and that the carrier concentration increased with increasing concentration of aluminum and gallium impurities. The gallium that diffused into the silicon substrate was identified as having originated from the gallium that decomposed on the reactor wall during the growth process and the gallium introduced onto the silicon substrate during GaN growth. In contrast, the amount of aluminum that diffused into the substrate was influenced by the duration of the trimethylaluminum (TMAl) flow: A long duration of the TMAl flow step before AlN growth led to a high aluminum concentration near the substrate surface.

    DOI: 10.7567/1347-4065/ab2657

    Web of Science

    Scopus

  145. Ammonia decomposition and reaction by high-resolution mass spectrometry for group III - Nitride epitaxial growth

    Ye Zheng, Nitta Shugo, Nagamatsu Kentaro, Fujimoto Naoki, Kushimoto Maki, Deki Manato, Tanaka Atsushi, Honda Yoshio, Pristovsek Markus, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   516 巻   頁: 63-66   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2019.03.025

    Web of Science

  146. Direct evidence of Mg diffusion through threading mixed dislocations in GaN p-n diodes and its effect on reverse leakage current

    Usami Shigeyoshi, Mayama Norihito, Toda Kazuya, Tanaka Atsushi, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS LETTERS   114 巻 ( 23 ) 頁: 232105   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5097767

    Web of Science

  147. Computational fluid dynamics simulation study of the gas flow balance in a vertical HVPE reactor with a showerhead for low cost bulk GaN crystal growth

    Liu Qiang, Fujimoto Naoki, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( SC ) 頁: SC1055   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    In order to make low cost bulk GaN single crystal with a high growth rate, we have built a vertical HVPE reactor with a showerhead configuration. The flow from the showerhead of the reactor is independently controlled by inner/outer two sets of gas supply lines. This special showerhead design makes the flow model different from the conventional showerhead reactors. We have employed a finite element-based simulator to study the fluid dynamic and crystal growth of this inner/outer flow independently controlled showerhead. Two simulation experiments were performed. One experiment has demonstrated that both growth rate and Ga yield can be improved without compromising the uniformity by controlling the different input parameters of inner and outer flow on the showerhead, as compared with the conventional showerhead. The other experiment has demonstrated that the showerhead can be further optimized by changing the inner/outer area ratio and input parameters.

    DOI: 10.7567/1347-4065/ab124e

    Web of Science

    Scopus

  148. Monolithic integration of tricolor micro-LEDs and color mixing investigation by analog and digital dimming

    Robin Yoann, Hemeret Francois, D'Inca Gillian, Pristovsek Markus, Trassoudaine Agnes, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( SC ) 頁: SCCC06   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    We report on the growth, processing and optical characterization of monolithically integrated tricolor micro-LEDs. The 100 × 100 μm2 active area of the devices is composed of independent subpixels emitting in the blue, green and yellow-orange range with color saturation of over 90% for all bands. The gamut of the device is recorded by both digital and analog dimming, i.e. by pulse width modulation or by varying the current density. Results indicate color mixing performed by both methods leads to a rotated or distorted gamut significantly different from the one predicted by the CIE color model. We explain our findings in terms of quantum-confined Stark effect screening and efficiency droop at high current density, which modify the expected hue and brightness of mixed colors.

    DOI: 10.7567/1347-4065/ab06ae

    Web of Science

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  149. Effect of photoelectrochemical etching and post-metallization annealing on gate controllability of AlGaN/GaN high electron mobility transistors

    Uemura Keisuke, Deki Manato, Honda Yoshio, Amano Hiroshi, Sato Taketomo

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( SC ) 頁: SCCD20   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    Recessed-gate AlGaN/GaN metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs) were fabricated by utilizing a photoelectrochemical (PEC) etching and a post-metallization annealing (PMA) process. In order to demonstrate the device performance and reliability, both electrical and optical electroluminescence (EL) properties were evaluated. The capacitance-voltage (C-V) characteristic showed that the PEC etching and subsequent PMA process enhanced the gate control of two-dimensional electron gas density. The PEC-etched-gate AlGaN/GaN MIS-HEMT showed the smallest sub-threshold slope of all the samples including planar-gate and inductively coupled plasma-etched-gate devices. Furthermore, the PEC-etched devices showed an extremely low 10-11 A mm-1 gate leakage current with no spot-like EL. These results indicated that the PEC etching and subsequent PMA process improved the electrical properties of the Al2O3/AlGaN interface, resulting in enhanced device performance of the AlGaN/GaN MIS-HEMTs.

    DOI: 10.7567/1347-4065/ab06b9

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  150. Deeply and vertically etched butte structure of vertical GaN p-n diode with avalanche capability

    Fukushima Hayata, Usami Shigeyoshi, Ogura Masaya, Ando Yuto, Tanaka Atsushi, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( SC ) 頁: SCCD25   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    A vertical p-n diode with a simple edge termination structure on a GaN free-standing substrate is demonstrated. The edge of this device is terminated simply by etching a drift layer deeply and vertically. A device simulation revealed that the electric field at the device edge was more relaxed and uniformly applied by etching the mesa deeper than the depletion region. The fabricated device showed low leakage current and avalanche capability, and its breakdown characteristics could be reproduced many times. By emission microscopy observation, we found that there was no leakage current at the side wall of the device and that avalanche breakdown occurred throughout the inside of the device. This indicates that the electric field crowding at the side wall of the device was completely suppressed and a uniform electric field distribution was obtained by this structure.

    DOI: 10.7567/1347-4065/ab106c

    Web of Science

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  151. Correlation between nanopipes formed from screw dislocations during homoepitaxial growth by metal-organic vapor-phase epitaxy and reverse leakage current in vertical p-n diodes on a free-standing GaN substrates

    Usami Shigeyoshi, Tanaka Atsushi, Fukushima Hayata, Ando Yuto, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( SC ) 頁: SCCB24   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    We fabricated p-n diodes under different growth pressures on free-standing GaN substrates of the same quality and observed a noteworthy difference in the reverse leakage current. A large reverse leakage current was generated by nanopipes, which were formed from screw dislocations in the homoepitaxial layer. There were two types of screw dislocation observed in this study. The first type already existed in the substrate and the other was newly generated in the epilayer by the coalescence of edge and mixed dislocations. An increase in the growth pressure suppressed the transformation of screw dislocations into nanopipes, which led to a reduction in the reverse leakage current. To reduce the leakage current further, it is necessary to apply growth conditions that do not transform screw dislocation into nanopipes and to use a free-standing substrate without threading dislocations, that become nanopipes.

    DOI: 10.7567/1347-4065/ab1250

    Web of Science

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  152. Controlling the orientations of directional sputtered non- and semi-polar GaN/AlN layers

    Nan Hu, Dinh Duc V., Pristovsek Markus, Honda Yoshio, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( SC ) 頁: SC1044   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    We have studied the impact on the surface orientation of different sputtered Al layers followed by AlN layers sputtered on m-plane sapphire. These initial layers were then overgrown by AlN and followed by GaN using metal-organic vapor phase epitaxy (MOVPE). By increasing sputtering time of the initial Al layer from 0 s to 15 s, we obtained single phase (10-10), (10-13) and (10-14) GaN/AlN layers. The thickness of the initial Al layer was estimated by optical transmission measurements to be about 0.5-1 nm for the (10-13) orientation, and >1 nm for the (10-14) orientation. After MOVPE growth, no trace of metallic Al was found by transmission electron microscopy, indicating that this layer was fully converted to AlN.

    DOI: 10.7567/1347-4065/ab1252

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  153. Comparison of AlxGa1-xN multiple quantum wells designed for 265 and 285nm deep-ultraviolet LEDs grown on AlN templates having macrosteps

    Nagasawa Yosuke, Kojima Kazunobu, Hirano Akira, Ipponmatsu Masamichi, Honda Yoshio, Amano Hiroshi, Akasaki Isamu, Chichibu Shigefusa F.

    APPLIED PHYSICS EXPRESS   12 巻 ( 6 ) 頁: 064009   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/1882-0786/ab21a9

    Web of Science

  154. Narrow Excitonic Lines in Core-Shell Nanorods With InGaN/GaN Quantum Wells Intersected by Basal Stacking Faults

    Evropeitsev Evgeniy A., Robin Yoann, Shubina Tatiana V., Bae Si-Young, Nitta Shugo, Kirilenko Demid A., Davydov Valery Y., Smirnov Alexandr N., Toropov Alexey A., Kushimoto Maki, Ivanov Sergey V., Amano Hiroshi

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   256 巻 ( 6 ) 頁: 1800648   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssb.201800648

    Web of Science

  155. Morphological study of InGaN on GaN substrate by supersaturation (vol 508, pg 58, 2019)

    Liu Zhibin, Nitta Shugo, Robin Yoann, Kushimoto Maki, Deki Manato, Honda Yoshio, Pristovsek Markus, Sitar Zlatko, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   514 巻   頁: 13-13   2019年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2019.02.058

    Web of Science

  156. Effect of substrate misorientation on the concentration of impurities and surface morphology of an epitaxial GaN layer on N-polar GaN substrate by MOVPE

    Nagamatsu Kentaro, Ando Yuto, Kono Tsukasa, Cheong Heajeong, Nitta Shugo, Honda Yoshio, Pristovsek Markus, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   512 巻   頁: 78-83   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2019.02.013

    Web of Science

  157. Nonpolar m-plane AlxGa1-xN layers grown on m-plane sapphire by MOVPE

    Duc V Dinh, Amano Hiroshi, Pristovsek Markus

    JOURNAL OF CRYSTAL GROWTH   512 巻   頁: 100-104   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2019.02.020

    Web of Science

  158. The emergence and prospects of deep-ultraviolet light-emitting diode technologies

    Kneissl Michael, Seong Tae-Yeon, Han Jung, Amano Hiroshi

    NATURE PHOTONICS   13 巻 ( 4 ) 頁: 233-244   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41566-019-0359-9

    Web of Science

  159. GaN drift-layer thickness effects in vertical Schottky barrier diodes on free-standing HVPE GaN substrates

    Sandupatla A., Arulkumaran S., Ng G. I., Ranjan K., Deki M., Nitta S., Honda Y., Amano H.

    AIP ADVANCES   9 巻 ( 4 ) 頁: 045007   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5087491

    Web of Science

  160. Transfer-free fabrication of a graphene transparent electrode on a GaN-based light-emitting diode using the direct precipitation method

    Yamada Jumpei, Usami Shigeyoshi, Ueda Yuki, Honda Yoshio, Amano Hiroshi, Maruyama Takahiro, Naritsuka Shigeya

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( 4 ) 頁: 040904   2019年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    In order to advance the mass production of graphene devices, it is beneficial to avoid the difficulty graphene transfer process. Direct precipitation of graphene using a tungsten capping layer is convenient for this purpose, and is quite simple and compatible with conventional semiconductor fabrication processes. In this study, multilayer graphene was directly precipitated on a wafer of GaN-based blue LEDs to form a transparent electrode. The fabricated LED exhibited superior I-V characteristics and emitted blue luminescence around the probe of the electrode.

    DOI: 10.7567/1347-4065/aafe70

    Web of Science

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  161. Effect of gas phase temperature on InGaN grown by metalorganic vapor phase epitaxy

    Liu Zhibin, Nitta Shugo, Usami Shigeyoshi, Robin Yoann, Kushimoto Maki, Deki Manato, Honda Yoshio, Pristovsek Markus, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   509 巻   頁: 50-53   2019年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2018.12.007

    Web of Science

  162. GaN-on-Si resonant-cavity light-emitting diode incorporating top and bottom dielectric distributed Bragg reflectors

    Cai Wei, Yuan Jialei, Ni Shuyu, Shi Zheng, Zhou Weidong, Liu Yuhuai, Wang Yongjin, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   12 巻 ( 3 ) 頁: 032004   2019年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/1882-0786/ab023c

    Web of Science

  163. Fully Ion Implanted Normally-Off GaN DMOSFETs with ALD-Al2O3 Gate Dielectrics

    Yoshino Michitaka, Ando Yuto, Deki Manato, Toyabe Toru, Kuriyama Kazuo, Honda Yoshio, Nishimura Tomoaki, Amano Hiroshi, Kachi Tetsu, Nakamura Tohru

    MATERIALS   12 巻 ( 5 ) 頁: 689   2019年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3390/ma12050689

    Web of Science

  164. Effects of Drift Layer Thicknesses in Reverse Conduction Mechanism on Vertical GaN-on-GaN SBDs grown by MOCVD

    Abhinay S., Arulkumaran S., Ng G.I., Ranjan K., Deki M., Nitta S., Honda Y., Amano H.

    2019 Electron Devices Technology and Manufacturing Conference, EDTM 2019     頁: 106 - 108   2019年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:2019 Electron Devices Technology and Manufacturing Conference, EDTM 2019  

    Effect of drift layer thicknesses (DLT) (2, 15 and 30 μm) in reverse current conduction mechanisms of vertical GaN-on-GaN Schottky Barrier Diodes grown MOCVD has been investigated for the first time. The conduction mechanism is changing from thermionic field emission (TFE) to thermionic emission (TE) when the DLT of GaN increases. The SBDs with DLT of 2 μm and 30 μm exhibit TFE through Poole-Frenkel emission and TE, respectively. However, the SBDs with DLT of 15 μm exhibit both TFE and TE. Activation energy (Ea) of traps was also calculated to be 0.69 eV for 2 μm, 0.38 for 15 μm and 0.4 eV for 30 μm respectively. Ea of 0.69 eV and 0.4 eV could be associated with screw threading dislocations and the presence of Mg in the grown drift layer, respectively.

    DOI: 10.1109/EDTM.2019.8731215

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  165. Morphological study of InGaN on GaN substrate by supersaturation

    Liu Zhibin, Nitta Shugo, Robin Yoann, Kushimoto Maki, Deki Manato, Honda Yoshio, Pristovsek Markus, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   508 巻   頁: 58-65   2019年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2018.12.028

    Web of Science

  166. How to obtain metal-polar untwinned high-quality (10-13) GaN on m-plane sapphire

    Hu Nan, Dinh Duc V., Pristovsek Markus, Honda Yoshio, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   507 巻   頁: 205 - 208   2019年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Crystal Growth  

    Directional sputtering of Al and AlN on (1 0 −1 0) sapphire was used to obtain metal-polar (1 0 −1 3) templates. After overgrowth with AlN and GaN using metal-organic vapor phase epitaxy, we obtained untwinned (1 0 −1 3) GaN layers. Full width at half maximum of the X-ray rocking curve of symmetric (1 0 −1 3) GaN is less than 550 arcsec along both [3 0 −3 −2]GaN and [1 −2 1 0]GaN directions. Ga-polarity of the layers was confirmed by high-resolution scanning transmission electron microscopy. Careful optimization of time and temperature of the initial Al sputtered layer was a key parameter to achieve high quality GaN templates.

    DOI: 10.1016/j.jcrysgro.2018.11.013

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  167. 高感度電子線ホログラフィーによるGaN系半導体のドーパント濃度分布の観察

    仲野 靖孝, 松本 実子, 穴田 智史, 山本 和生, 石川 由加里, 平山 司, 安藤 悠人, 小倉 昌也, 田中 敦之, 本田 善央, 天野 浩

    まてりあ   58 巻 ( 2 ) 頁: 103 - 103   2019年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:公益社団法人 日本金属学会  

    DOI: 10.2320/materia.58.103

    CiNii Research

  168. Pole figure analysis from electron backscatter diffraction-an effective method of evaluating fiber-textured silicon thin films as seed layers for epitaxy

    Hainey Mel Jr., Robin Yoann, Amano Hiroshi, Usami Noritaka

    APPLIED PHYSICS EXPRESS   12 巻 ( 2 )   2019年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Because of their >95% (111) surface orientation and very large (10-300 μm) grain sizes, sub-50 nm Group IV thin films fabricated by metal-induced crystallization are promising seed layers for epitaxy. However, methods for evaluating Group IV film quality for subsequent homo-and heteroepitaxial growth have not been widely reported. Here, we show how pole figures obtained by electron backscatter diffraction allow for texture analysis and measurement of grain misorientation. Correlations with Group IV thin film processing parameters such as annealing temperature and film quality in heteroepitaxially grown GaN films are developed.

    DOI: 10.7567/1882-0786/aafb26

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  169. Vertical GaN p-n diode with deeply etched mesa and the capability of avalanche breakdown

    Fukushima Hayata, Usami Shigeyoshi, Ogura Masaya, Ando Yuto, Tanaka Atsushi, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   12 巻 ( 2 ) 頁: 026502   2019年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    A simple structure with high breakdown voltage and a low leakage current of a vertical GaN p-n diode on a GaN free-standing substrate is demonstrated. We describe a vertical p-n diode with a simple edge termination that has a drift layer etched deeply and vertically. A device simulation revealed that the electric field was more relaxed at the device edge and applied uniformly in the entire device with increasing etching depth. We fabricated the simulated structure and succeeded in reducing the leakage current and improving the breakdown voltage. With this structure, a stable avalanche breakdown can be observed.

    DOI: 10.7567/1882-0786/aafdb9

    Web of Science

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  170. Compositional control of homogeneous InGaN nanowires with the In content up to 90.

    Zeghouane M, Avit G, André Y, Bougerol C, Robin Y, Ferret P, Castelluci D, Gil E, Dubrovskii VG, Amano H, Trassoudaine A

    Nanotechnology   30 巻 ( 4 ) 頁: 044001   2019年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Nanotechnology  

    Homogenous InGaN nanowires with a controlled indium composition up to 90% are grown on GaN/c-Al2O3 templates by catalyst-free hydride vapor phase epitaxy using InCl3 and GaCl as group III element precursors. The influence of the partial pressures on the growth rate and composition of InGaN nanowires is investigated. It is shown how the InN mole fraction in nanowires can be finely tuned by changing the vapor phase composition. Thermodynamic calculations are presented that take into account different interconnected reactions in the vapor phase and show a good agreement with the compositional data. Energy dispersive x-ray spectroscopy profiles performed on single nanowires show a homogenous indium composition along the entire nanowire length. X-ray diffraction measurements performed on nanowires arrays confirm these data. High-resolution transmission electron microscopy analysis shows the wurtzite crystal structure with a reduced defect density for InGaN nanowires with the highest indium content.

    DOI: 10.1088/1361-6528/aaec39

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    PubMed

  171. Localization and transient emission properties in InGaN/GaN quantum wells of different polarities within core- shell nanorods

    Robin Y., Evropeitsev E. A., Shubina T. V., Kirilenko D. A., Davydov V. Yu., Smirnov A. N., Toropov A. A., Eliseyev I. A., Bae S. Y., Kushimoto M., Nitta S., Ivanov S. V., Amano H.

    NANOSCALE   11 巻 ( 1 ) 頁: 193 - 199   2019年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Nanoscale  

    Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K. The NRs exhibit three well-defined PL bands in the near-UV, blue, and green range ascribed to the emission of quantum well (QW) areas situated at the (1.00) sidewalls, (10.1) top facets, and (00.1) tip, respectively. At low temperature, time-resolved PL shows a fast decay time of about 0.5 ns for the semi- and non-polar QWs, while the polar QWs exhibit at least a twice-longer time. Rapid delocalization of carriers above 50 K indicates shallow potential fluctuations in the QWs. At room temperature, the characteristic fast PL decay time of the three QW bands stabilizes around 300 ps. The slow decaying PL components have different characteristic decay times that are explained by additional localization at basal stacking faults (BSFs), taking into account the quantum confined Stark effect. In addition, narrow excitonic luminescence lines are observed in the BSF-enriched polar QWs, providing direct evidence of the impact of the BSF/QW crossings on the optical properties of the NRs. A PL rise time of about 100 ps does not show any deviation between bands. These findings are suggestive of similar transport mechanisms in temperature equilibrium without inter-facet transport between different QWs. We believe that predictable transient characteristics can play a key role in creating uniform NR ensembles for device applications.

    DOI: 10.1039/c8nr05863f

    Web of Science

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  172. Carrier localization structure combined with current micropaths in AlGaN quantum wells grown on an AlN template with macrosteps

    Kojima K., Nagasawa Y., Hirano A., Ippommatsu M., Honda Y., Amano H., Akasaki I., Chichibu S.F.

    Applied Physics Letters   114 巻 ( 1 ) 頁: 011102   2019年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    The microscopic structural and optical characteristics of AlGaN-based light-emitting diodes grown on AlN templates with macrosteps were evaluated. Cross-sectional transmission electron microscopy in the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy reveal that the AlGaN cladding layer under the AlGaN quantum wells (QWs) has microscopic compositional modulations originating from the macrosteps at the AlN template surface. The Ga-rich oblique zones in the cladding layer likely behave as current micropaths. These micropaths are connected to the carrier localization structure, which is formed by the modulation of both the well widths and the compositions of the QWs. In-plane spatially-resolved cathodoluminescence (CL) spectroscopy indicated significant inhomogeneity of the CL characteristics: the brighter emission with a lower peak photon energy confirms the existence of the carrier localization structure in the QWs. Carrier localization in the QWs along with the current micropaths in the AlGaN cladding layer appears to increase the external quantum efficiency of AlGaN LEDs.

    DOI: 10.1063/1.5063735

    Web of Science

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  173. 286 nm monolithic multicomponent system

    Yuan Jialei, Jiang Yan, Shi Zheng, Gao Xumin, Wang Yongjin, Sun Xiaojuan, Li Dabing, Liu Yuhuai, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 巻 ( 1 ) 頁: 010909   2019年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    We present a 286 nm monolithic multicomponent system in which two identical multiple quantum well (MQW) diodes merge with a waveguide together on a single chip. The monolithic multicomponent system allows all existing standard fabrication processes and establishes an optical link between two MQW-diodes because of the simultaneous emission-detection phenomenon. One MQW-diode transcribes electronic information into an optical signal to be coupled into a waveguide. The guided light then propagates along the waveguide to the other MQW-diode that converts the optical signal into an electronic one. A spatial light transmission at 50 Mbps is demonstrated using non-return-to-zero on-off keying modulation.

    DOI: 10.7567/1347-4065/aaf3aa

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  174. Electronic structure analysis of core structures of threading dislocations in GaN

    Nakano Takashi, Chokawa Kenta, Araidai Masaaki, Shiraishi Kenji, Oshiyama Atsushi, Kusaba Akira, Kangawa Yoshihiro, Tanaka Atsushi, Honda Yoshio, Amano Hiroshi

    2019 COMPOUND SEMICONDUCTOR WEEK (CSW)     頁: .   2019年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  175. Light-Emitting Diodes Materials, Processes, Devices and Applications Foreword

    Amano Hiroshi

    LIGHT-EMITTING DIODES: MATERIALS, PROCESSES, DEVICES AND APPLICATIONS   4 巻   頁: V - V   2019年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  176. MOVPE growth and high-temperature annealing of (10(1)over-bar0) AlN layers on (10(1)over-bar0) sapphire

    Dinh Duc V., Amano Hiroshi, Pristovsek Markus

    JOURNAL OF CRYSTAL GROWTH   502 巻   頁: 14-18   2018年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2018.09.001

    Web of Science

  177. What is red? On the chromaticity of orange-red InGaN/GaN based LEDs

    Robin Y., Pristovsek M., Amano H., Oehler F., Oliver R. A., Humphreys C. J.

    JOURNAL OF APPLIED PHYSICS   124 巻 ( 18 ) 頁: 183102   2018年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    The full width at half maximum (FWHM) of the luminescence of visible InGaN quantum well (QW) based emitters increases with wavelength. This broadening of the luminescence decreases the color saturation from 100% to about 70% up a wavelength shorter than 515 nm. For emission wavelengths longer than 515 nm, the saturation surprisingly increases again and reaches 95% beyond 560 nm. More important, in the yellow-red range, the perceived hue is strongly blue-shifted by a broad emission. This phenomenon is known as Abney effect, and it originates from the spectral sensitivities of the cone cells of the human eyes. As a consequence, for red InGaN QW based LEDs, the peak wavelength must be even further in the red. Based on a large set of QWs grown on different crystal orientations, we correlated the wavelength and the luminescence FWHM of InGaN/GaN QWs to build a model which predicts the perceived chromaticity, i.e., the apparent hue and saturation of yellow-red nitride LEDs. We also applied this model to (11-22), a-plane, and m-plane QWs and compared our data to the state-of-the-art of the literature. We concluded that the FWHM of the luminescence is a critical parameter to design and a further challenge for red InGaN-based light-emitting diodes.

    DOI: 10.1063/1.5047240

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  178. Simultaneous Growth of Various InGaN/GaN Core-Shell Microstructures for Color Tunable Device Applications

    Robin Yoann, Liao Yaqiang, Pristovsek Markus, Amano Hiroshi

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   215 巻 ( 21 ) 頁: 1800361   2018年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (A) Applications and Materials Science  

    An approach to simultaneously grow independent core-shell structures emitting at different wavelengths by selective area epitaxy is presented. By using seeds of different sizes, the monolithic integration of various GaN crystals including elongated nano-rods (NRs), micro-platelets (MPs), and a range of pyramid-like structures are demonstrated. Dominant non-polar sidewalls cover more than 75% of the surface area of the NRs, while the polar top facet are about 80% of the total surface of the MPs. InGaN/GaN quantum wells (QWs) deposited on these structures exhibit independent and well-separated emissions in the green–blue and orange–red ranges, respectively. The pyramid-like structures at intermediate seed sizes are more complex with semi-polar facets nearly totaling 60% of the total surface area, resulting in yellow luminescence strongly broadened by the nearby facets contributions. These results suggest the total surface area of each facets and the resulting optical properties of the crystals can be tailored by adjusting the size of the seeds. However, further improvements are required to locally enhance the vertical, pyramidal, and lateral growth of the GaN cores and increase the spectral purity of the different QWs. The approach presented is of interest to design multi-wavelength devices which requires independent subpixels of high color purity.

    DOI: 10.1002/pssa.201800361

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  179. Analysis of negative electron affinity InGaN photocathode by temperature-programed desorption method

    Kashima Masahiro, Sato Daiki, Koizumi Atsushi, Nishitani Tomohiro, Honda Yoshio, Amano Hiroshi, Iijima Hokuto, Meguro Takashi

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B   36 巻 ( 6 ) 頁: 06JK02   2018年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics  

    A III-V semiconductor with a few monolayers of alkali metals (e.g., Cs) forms a negative electron affinity (NEA) surface, for which the vacuum level lies below the conduction band minimum of the base semiconductor. The photocathodes that form an NEA surface (NEA photocathodes) have various advantages, such as low emittance, a large current, high spin polarization, and ultrashort pulsed operation. The NEA-InGaN photocathode, which is sensitive to blue light, has been studied as a material for the next-generation robust photocathode. However, the proper conditions for forming NEA surfaces remain unknown. The authors consider whether the suitable process for NEA surfaces can be understood by investigating the relationship between the electron emission and the adsorption state of alkali metals. In this study, the relationship between the electron emission and the adsorption state of Cs on the p-type InGaN (0001) was analyzed by the temperature-programed desorption (TPD) method using a quadrupole mass spectrometer. From the results of the TPD measurements, it was shown that there were several adsorption states of Cs on InGaN. The quantum efficiency (QE), which indicates the ratio of emitted electrons to incident photons, increased while Cs desorption occurred. The authors divided the formation process of an NEA surface into several sections to investigate the adsorption states of Cs related to the electron emission and to discuss the reasons why the QE increased despite the desorbed Cs. From the results of the NEA activation in each section, it was shown that there were sections where the QE increased by reacting with O2 after Cs supply stopped. There is a possibility that several layers reacting with O2 and those not reacting with O2 are formed by performing NEA activation until the QE saturates. From the results of the TPD measurements in each section, it was suggested that there was a Cs peak at above 700 °C when the TPD method was carried out immediately after confirming the electron emission. Therefore, the adsorption state of Cs that formed a peak at above 700 °C had a close relation to the electron emission. It is considered that the increase of the QE in the TPD was affected by adsorbed Cs compounds that reacted with O2. Although the mechanism is not understood, it is known that the QE was increased by the reaction of Cs adsorbed compounds and O2 in previous studies. It was suspected that layers that reacted with O2 appeared from TPD and then the QE increased by reacting with O2.

    DOI: 10.1116/1.5048061

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  180. Full-duplex light communication with a monolithic multicomponent system

    Wang Yongjin, Wang Xin, Zhu Bingcheng, Shi Zheng, Yuan Jialei, Gao Xumin, Liu Yuhuai, Sun Xiaojuan, Li Dabing, Amano Hiroshi

    LIGHT-SCIENCE & APPLICATIONS   7 巻   頁: 83   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41377-018-0083-0

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  181. Crystal engineering by tuning the growth kinetics of GaN 3-D microstructures in SAG-HVPE

    Avit Geoffrey, Zeghouane Mohammed, Andre Yamina, Castelluci Dominique, Gil Evelyne, Bae Si-Young, Amano Hiroshi, Trassoudaine Agnes

    CRYSTENGCOMM   20 巻 ( 40 ) 頁: 6207 - 6213   2018年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CrystEngComm  

    The growth of GaN 3-D microstructures is investigated by SAG-HVPE. Capitalizing on the properties of this kinetically-controlled process, the main experimental parameters and physical mechanisms that control the shaping of 3D GaN prisms and pyramids in SAG-HVPE are highlighted. Growth experiments performed on N-polar AlN/Si(100) and Ga-polar GaN/Si(111) substrates also provide insight into how to switch from a pyramid to a prismatic shape for a given substrate polarity. The aspect ratio of GaN rods could be tuned by playing with the HCl partial pressure additionally introduced during growth. The influence of both mass transport and surface kinetics is discussed, as the crystal growth rate varies with increasing surface area as time goes by. Ammonia treatment prior to the growth, aimed at blocking the r planes thanks to H2 passivation, is proposed to tune the morphology of the GaN rods. Raman spectroscopy performed on individual GaN rods shows no relevant strain field and no structural differences between the rods and state-of-the-art bulk GaN.

    DOI: 10.1039/c8ce01177j

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  182. Comparing high-purity c- and m-plane GaN layers for Schottky barrier diodes grown homoepitaxially by metalorganic vapor phase epitaxy

    Nagamatsu Kentaro, Ando Yuto, Ye Zheng, Barry Ousmane, Tanaka Atsushi, Deki Manato, Nitta Shugo, Honda Yoshio, Pristovsek Markus, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 巻 ( 10 ) 頁: 105501   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/JJAP.57.105501

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  183. High-temperature thermal annealing of nonpolar (10(1)over-bar0) AlN layers sputtered on (1 0(1)over-bar0) sapphire

    Dinh Duc V, Hu Nan, Honda Yoshio, Amano Hiroshi, Pristovsek Markus

    JOURNAL OF CRYSTAL GROWTH   498 巻   頁: 377-380   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2018.07.015

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  184. 「材料研究の楽しさ」

    天野 浩

    表面と真空   61 巻 ( 9 ) 頁: 565 - 567   2018年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:公益社団法人 日本表面真空学会  

    半導体の王者は言わずと知れたSiである。市場規模を比べると,化合物半導体全部含めてもSiの1/10にも満たない。それでも化合物半導体,とりわけGaN系窒化物半導体にこだわっている理由は,この材料の物性自体がとても興味深いこと,およびSiでは出来ないことが出来る,或いは今後できそうだからである。本寄稿では,筆者が学生の頃からこれまで30年以上もの間取り組んでいるGaN系窒化物半導体材料の研究で,特に表面と真空について学んだことを中心に書かせて頂くことにする。

    DOI: 10.1380/vss.61.565

    CiNii Research

  185. Detailed study of effects of duration of pre-AIN-growth trimethylaluminum step on morphologies of GaN layers grown on silicon substrate by metal organic chemical vapor deposition

    Matsumoto Koji, Ono Toshiaki, Honda Yoshio, Murakami Satoshi, Kushimoto Maki, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 巻 ( 9 ) 頁: 091001   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/JJAP.57.091001

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  186. Reduction of Residual Impurities in Homoepitaxial m-Plane (10(1)over-bar0) GaN by Using N-2 Carrier Gas in Metalorganic Vapor Phase Epitaxy

    Barry Ousmane I., Lekhal Kaddour, Bae Si-Young, Lee Ho-Jun, Pristovsek Markus, Honda Yoshio, Amano Hiroshi

    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS   12 巻 ( 8 ) 頁: 1800124   2018年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi - Rapid Research Letters  

    The reduction of unintentional impurities in m-plane (1010) GaN homoepitaxial layers is demonstrated by using nitrogen (N2), as opposed to hydrogen (H2), as carrier gas in metalorganic vapor phase epitaxy (MOVPE). Secondary ion mass spectrometry (SIMS) analysis shows that the impurity levels of residual oxygen (O), carbon (C), and silicon (Si) are decreased by nearly one order of magnitude in N2-grown samples. Although the full width at half maximum (FWHM) values for the on-axis m-plane X-ray rocking curves of all specimens are quite similar (around 50 arcsec), plan-view scanning transmission electron microscopy (STEM) measurements reveal a clear reduction of dislocation densities in N2-grown films. Their origin is likely related to an initial surface roughening with H2 carrier gas, which also causes surface faceting resulting in the formation of large four-sided pyramidal hillocks, while using N2 results in smoother surfaces. Hence, MOVPE growth with N2 carrier gas is an effective method to lower the impurity incorporation in m-plane GaN materials in addition to reducing the formation of defects and improving the surface morphology, which can enable the development of high-performance GaN-based devices on non-polar surfaces.

    DOI: 10.1002/pssr.201800124

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  187. Improvement of breakdown voltage of vertical GaN p-n junction diode with Ga2O3 passivated by sputtering

    Ueoka Yoshihiro, Deki Meneto, Honda Yoshio, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 巻 ( 7 ) 頁: 070302   2018年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Journal of Applied Physics  

    This article describes a new passivation process of Ga2O3, which consists by sputtering, for a vertical GaN p-n junction diode on a free-standing GaN substrate with a field-plate (FP) structure. We demonstrated reduced plasma damage during the sputtering process by cure annealing, and succeeded in improving the breakdown voltage (VB) to -550V with the FP, compared with VB of -200V without the FP. Ga2O3 is a suitable material for the FP because its dielectric constant is similar to that of GaN and it is more easily etched than Al2O3, which is used as a conventional insulator.

    DOI: 10.7567/JJAP.57.070302

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  188. Study on the Main-Chain Structure of Amorphous Fluorine Resins for Encapsulating AlGaN-Based DUV-LEDs

    Yamada Kiho, Nagasawa Yosuke, Nagai Shoko, Hirano Akira, Ippommatsu Masamichi, Aosaki Ko, Honda Yoshio, Amano Hiroshi, Akasaki Isamu

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   215 巻 ( 10 ) 頁: 1700525   2018年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (A) Applications and Materials Science  

    The main chain structure of optically isotropic amorphous fluorine resin for encapsulating AlGaN-based deep-ultraviolet LEDs (λ < 300 nm) is studied. One type of amorphous fluorine resin has a five-membered ring with a single oxygen atom and the other has that one with two oxygen atoms. Reliability testing is performed using AlGaN-based LEDs of 262 and 289 nm. For the resin with two oxygen atoms in the ring, visible damage to the electrode and significantly increased leakage current are considered to been caused by the photolysis of the ring induced by irradiation with deep-ultraviolet light. In contrast, electrode damage and increased leakage are not observed in the case of the resin with the single-oxygen ring.

    DOI: 10.1002/pssa.201700525

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  189. Insight into the performance of multi-color InGaN/GaN nanorod light emitting diodes

    Robin Y., Bae S. Y., Shubina T. V., Pristovsek M., Evropeitsev E. A., Kirilenko D. A., Davydov V. Yu., Smirnov A. N., Toropov A. A., Jmerik V. N., Kushimoto M., Nitta S., Ivanov S. V., Amano H.

    SCIENTIFIC REPORTS   8 巻   頁: 7311   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41598-018-25473-x

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  190. m-Plane GaN Schottky Barrier Diodes Fabricated With MOVPE Layer on Several Off-Angle m-Plane GaN Substrates

    Tanaka Atsushi, Ando Yuto, Nagamatsu Kentaro, Deki Manato, Cheong Heajeong, Ousmane Barry, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   215 巻 ( 9 ) 頁: 1700645   2018年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (A) Applications and Materials Science  

    In this study, GaN m-plane Schottky barrier diodes are fabricated by metalorganic vapor-phase epitaxy (MOVPE) on several off-angle gallium nitride (GaN) substrates, and the off-cut angle dependence of impurity incorporation is investigated. We show that the MOVPE layer on the substrate inclined 5° toward the [000–1] direction has extremely low impurity incorporation. These results provide important suggestions for the fabrication of m-plane power devices.

    DOI: 10.1002/pssa.201700645

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  191. Transferrable monolithic multicomponent system for near-ultraviolet optoelectronics

    Qin Chuan, Gao Xumin, Yuan Jialei, Shi Zheng, Jiang Yuan, Liu Yuhuai, Wang Yongjin, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   11 巻 ( 5 ) 頁: 051201   2018年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    A monolithic near-ultraviolet multicomponent system is implemented on a 0.8-mm-diameter suspended membrane by integrating a transmitter, waveguide, and receiver into a single chip. Two identical InGaN/Al0.10Ga0.90N multiple-quantum well (MQW) diodes are fabricated using the same process flow, which separately function as a transmitter and receiver. There is a spectral overlap between the emission and detection spectra of the MQW diodes. Therefore, the receiver can respond to changes in the emission of the transmitter. The multicomponent system is mechanically transferred from silicon, and the wire-bonded transmitter on glass experimentally demonstrates spatial light transmission at 200 Mbps using non-return-to-zero on–off keying modulation.

    DOI: 10.7567/APEX.11.051201

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  192. Interface amorphization in hexagonal boron nitride films on sapphire substrate grown by metalorganic vapor phase epitaxy

    Yang Xu, Nitta Shugo, Pristovsek Markus, Liu Yuhuai, Nagamatsu Kentaro, Kushimoto Maki, Honda Yoshio, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   11 巻 ( 5 ) 頁: 051002   2018年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Express  

    Hexagonal boron nitride (h-BN) films directly grown on c-plane sapphire substrates by pulsed-mode metalorganic vapor phase epitaxy exhibit an interlayer for growth temperatures above 1200 °C. Cross-sectional transmission electron microscopy shows that this interlayer is amorphous, while the crystalline h-BN layer above has a distinct orientational relationship with the sapphire substrate. Electron energy loss spectroscopy shows the energy-loss peaks of B and N in both the amorphous interlayer and the overlying crystalline h-BN layer, while Al and O signals are also seen in the amorphous interlayer. Thus, the interlayer forms during h-BN growth through the decomposition of the sapphire at elevated temperatures.

    DOI: 10.7567/APEX.11.051002

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  193. Correlation between dislocations and leakage current of p-n diodes on a free-standing GaN substrate

    Usami Shigeyoshi, Ando Yuto, Tanaka Atsushi, Nagamatsu Kentaro, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Amano Hiroshi, Sugawara Yoshihiro, Yao Yong-Zhao, Ishikawa Yukari

    APPLIED PHYSICS LETTERS   112 巻 ( 18 ) 頁: 182106   2018年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Physics Letters  

    Dislocations that cause a reverse leakage current in vertical p-n diodes on a GaN free-standing substrate were investigated. Under a high reverse bias, dot-like leakage spots were observed using an emission microscope. Subsequent cathodoluminescence (CL) observations revealed that the leakage spots coincided with part of the CL dark spots, indicating that some types of dislocation cause reverse leakage. When etch pits were formed on the dislocations by KOH etching, three sizes of etch pits were obtained (large, medium, and small). Among these etch pits, only the medium pits coincided with leakage spots. Additionally, transmission electron microscopy observations revealed that pure screw dislocations are present under the leakage spots. The results revealed that 1c pure screw dislocations are related to the reverse leakage in vertical p-n diodes.

    DOI: 10.1063/1.5024704

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  194. Light output performance of red AlGaInP-based light emitting diodes with different chip geometries and structures

    Oh Jeong-Tak, Lee Sang-Youl, Moon Yong-Tae, Moon Ji Hyung, Park Sunwoo, Hong Ki Yong, Song Ki Young, Oh Chan-Hyoung, Shim Jong-In, Jeong Hwan-Hee, Song June-O, Amano Hiroshi, Seong Tae-Yeon

    OPTICS EXPRESS   26 巻 ( 9 ) 頁: 11194-11200   2018年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1364/OE.26.011194

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  195. The 2018 GaN power electronics roadmap

    Amano H., Baines Y., Beam E., Borga Matteo, Bouchet T., Chalker Paul R., Charles M., Chen Kevin J., Chowdhury Nadim, Chu Rongming, De Santi Carlo, De Souza Maria Merlyne, Decoutere Stefaan, Di Cioccio L., Eckardt Bernd, Egawa Takashi, Fay P., Freedsman Joseph J., Guido L., Haeberlen Oliver, Haynes Geoff, Heckel Thomas, Hemakumara Dilini, Houston Peter, Hu Jie, Hua Mengyuan, Huang Qingyun, Huang Alex, Jiang Sheng, Kawai H., Kinzer Dan, Kuball Martin, Kumar Ashwani, Lee Kean Boon, Li Xu, Marcon Denis, Maerz Martin, McCarthy R., Meneghesso Gaudenzio, Meneghini Matteo, Morvan E., Nakajima A., Narayanan E. M. S., Oliver Stephen, Palacios Tomas, Piedra Daniel, Plissonnier M., Reddy R., Sun Min, Thayne Iain, Torres A., Trivellin Nicola, Unni V., Uren Michael J., Van Hove Marleen, Wallis David J., Wang J., Xie J., Yagi S., Yang Shu, Youtsey C., Yu Ruiyang, Zanoni Enrico, Zeltner Stefan, Zhang Yuhao

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   51 巻 ( 16 ) 頁: 163001   2018年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    DOI: 10.1088/1361-6463/aaaf9d

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  196. Growth of hexagonal boron nitride on sapphire substrate by pulsed-mode metalorganic vapor phase epitaxy

    Yang Xu, Nitta Shugo, Nagamatsu Kentaro, Bae Si-Young, Lee Ho-Jun, Liu Yuhuai, Pristovsek Markus, Honda Yoshio, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   482 巻 ( 15 ) 頁: 1 - 8   2018年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Crystal Growth  

    Hexagonal boron nitride (h-BN) was directly grown on sapphire substrate using alternating ammonia (NH3) and triethylboron (TEB) supply (pulsed mode) in metalorganic vapor phase epitaxy. The best condition is when just enough NH3 is supplied to fully convert the TEB within one cycle. Excess NH3 caused islands on h-BN film surface while a lack of NH3 does not form h-BN at all. The epitaxial relationship between grown h-BN layer and c-plane sapphire was confirmed to be [0001]h-BN∥[0001]sapphire and [10-10]h-BN∥[11-20]sapphire. It is known that, compared to AlN, BN requires higher V/III ratios for good crystallinity, which due to severe gas-phase reactions is difficult to achieve using continuous supply. Thus using pulsed mode the FWHM of the symmetric (0002) diffraction was almost halved and the growth rate was several times faster.

    DOI: 10.1016/j.jcrysgro.2017.10.036

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  197. Electrical and Thermal Analysis of Vertical GaN-on-GaN PN Diodes

    Yates Luke, Pavlidis Georges, Graham Samuel, Usami Shigeyoshi, Nagamatsu Kentaro, Honda Yoshio, Amano Hiroshi

    PROCEEDINGS OF THE 17TH IEEE INTERSOCIETY CONFERENCE ON THERMAL AND THERMOMECHANICAL PHENOMENA IN ELECTRONIC SYSTEMS (ITHERM 2018)     頁: 831-837   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  198. Theoretical Study of the Electronic Structure of Threading Edge Dislocations in GaN

    Nakano Takashi, Araidai Masaaki, Shiraishi Kenji, Tanaka Atsushi, Honda Yoshio, Amano Hiroshi

    GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 8   86 巻 ( 12 ) 頁: 41 - 49   2018年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ECS Transactions  

    It is very important to fabricate high-quality GaN especially used for power devices. However, threading dislocations degrade the performance of GaN-based electronic devices. It is necessary to examine the electronic behavior at threading dislocations in GaN and to clarify the origin of the leakage current. As for theoretical studies, the electronic structure of threading dislocations in GaN is not fully understood. We investigated whether threading edge dislocations contribute to the leakage current or not. To do this, we used first principles calculations based on density functional theory (DFT) to examine the electronic structure at threading edge dislocations with Burgers vectors of 1/3[11-20]. We examined four core types of atomic structure at threading edge dislocations which contains about 200 atoms. Compared with dislocation line energies of each core configurations, it was found that the 5/7-atoms ring core and 8-atoms ring core are energetically stable. Then, we analyzed the electronic densities of states of each core configurations, and it was found that all types of core configurations at threading edge dislocations do not contribute to leakage current in n-type GaN-based devices.

    DOI: 10.1149/08612.0041ecst

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  199. DFT modeling of carbon incorporation in GaN(0001) and GaN(000(1)over-bar) metalorganic vapor phase epitaxy 査読有り

    Pawel Kempisty, Yoshihiro Kangawa, Akira Kusaba, Kenji Shiraishi, Stanislaw Krukowski, Michal Bockowski, Koichi Kakimoto, and Hiroshi Amano

    APPLIED PHYSICS LETTERS   111 巻   頁: 141602/1-5   2017年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The carbon incorporation mechanism in GaN(0001) and GaN(000 (1) over bar) during MOVPE was investigated using density functional theory (DFT) calculations. The results confirm that the crucial factors for carbon incorporation are Fermi level pinning and accompanying surface band bending. In addition, the lattice symmetry has a strong dependence on the stability of carbon in a few subsurface layers, which results from interactions between the impurities and surface states. It was shown that these effects are responsible for facilitating or hindering the incorporation of impurities and dopants. The influence of diluent gas species (hydrogen or nitrogen) on carbon incorporation was discussed.

    DOI: 10.1063/1.4991608

  200. Initial leakage current paths in the vertical-type GaN-on-GaN Schottky barrier diodes

    Liwen Sang, Bing Ren, Masatomo Sumiya, Meiyong Liao, Yasuo Koide, Atsushi Tanaka, Yujin Cho, Yoshitomo Harada, Toshihide Nabatame, Takashi Sekiguchi, Shigeyoshi Usami, Yoshio Honda, and Hiroshi Amano

    APPLIED PHYSICS LETTERS   111 巻   頁: 122102/1-5   2017年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electrical characteristics of leakage current paths in vertical-type n-GaN Schottky barrier diodes (SBDs) on free-standing GaN substrates are investigated by using photon emission microscopy (PEM). The PEM mapping shows that the initial failure of the SBD devices at low voltages is due to the leakage current paths from polygonal pits in the GaN epilayers. It is observed that these polygonal pits originate from carbon impurity accumulation to the dislocations with a screw-type component by microstructure analysis. For the SBD without polygonal pits, no initial failure is observed and the first leakage appeals at the edge of electrodes as a result of electric field concentration. The mechanism of leakage at pits is explained in terms of trap assisted tunneling through fitting current-voltage characteristics.

    DOI: 10.1063/1.4994627

  201. Absolute technique for measuring internal electric fields in InGaN/GaN light-emitting diodes by electroreflectance applicable to all crystal orientations 査読有り

    Tomoyuki Tanikawa, Kanako Shojiki, Ryuji Katayama, Shigeyuki Kuboya, Takashi Matsuoka, Yoshio Honda, and Hiroshi Amano

    Applied Physics Express   10 巻   頁: 082101/1-4   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/APEX.10.082101

  202. Low cost high voltage GaN polarization superjunction field effect transistors

    Kawai H., Yagi S., Hirata S., Nakamura F., Saito T., Kamiyama Y., Yamamoto M., Amano H., Unni V., Narayanan E. M. S.

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   214 巻 ( 8 ) 頁: 1600834/1-10   2017年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (A) Applications and Materials Science  

    A comprehensive overview of the novel high voltage GaN field effect transistors (FETs) based on the Polarization Superjunction (PSJ) concept, and a cost-effective approach towards manufacturing these high performance devices are presented. Current challenges impeding wider adoption of GaN power switching transistors in applications, and the latest results of the scaled-up PSJ-FETs from POWDEC KK, are also discussed. The article also presents hard-switching characteristics of 400–800 V boost converter, constructed using a PSJ-FET grown on sapphire substrate, and the future direction of GaN power semiconductor technology based on monolithic integration for advanced power electronics.

    DOI: 10.1002/pssa.201600834

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  203. Facet dependence of leakage current and carrier concentration in m-plane GaN Schottky barrier diode fabricated with MOVPE 査読有り

    Atsushi Tanaka, Ousmane1 Barry, Kentaro Nagamatsu, Junya Matsushita, Manato Deki, Yuto Ando, Maki Kushimoto, Shugo Nitta, Yoshio Honda, and Hiroshi Amano

    Phys. Status Solidi A   214 巻 ( 8 ) 頁: 1600829/1-5   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In this study, GaN m-plane Schottky barrier diodes fabricated with a metalorganic vapor-phase epitaxy on a GaN substrate were investigated using emission microscope, photoluminescence, and cathodoluminescence. In addition, facet dependence of leakage current under reverse-biased condition was observed. We showed that the leakage-current distribution was caused by the facet dependence of the carrier concentration and oxygen concentration. These results can provide important suggestions for the fabrication of m-plane devices. (a) four-faceted hillocks on m-plane GaN MOVPE sample, facet dependence of (b) leakage current and (c) PL peak intensity of the m-plane GaN Schottky barrier diode.

    DOI: 10.1002/pssa.201600829

  204. Effect of dislocations on the growth of p-type GaN and on the characteristics of p–n diodes 招待有り 査読有り

      214 巻 ( 8 ) 頁: 1600837/1-5   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssb.201600722

  205. Selective-area growth of doped GaN nanorods by pulsed-mode MOCVD: Effect of Si and Mg dopants 査読有り

    Si-Young Bae, Kaddour Lekhal, Ho-Jun Lee, Jung-Wook Min, Dong-Seon Lee, Yoshio Honda, and Hiroshi Amano

    Phys. Status Solidi B   254 巻 ( 8 ) 頁: 1600722/1-7   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Injecting current with a uniform carrier concentration is important for applications with three-dimensional architectures such as vertical power devices or displays. In III-nitride nanostructures, dopants not only incorporate differently depending on the surface orientation but can also seriously affect the kinetic equilibrium shapes of the nanorods. Herein, we report selective-area growth of doped GaN nanorods grown by pulsed-mode metalorganic chemical vapor deposition. Two dopants, Si and Mg, were employed as donor and acceptor atoms, respectively, for a mono-doping approach. Furthermore, a mixed flow of Si and Mg was supplied for a co-doping approach. We compared the morphological effects and growth rates of each doped GaN nanorod array. Then, we proposed appropriate growth mechanisms for the doped GaN nanorods on the basis of our structural characterizations. These results might extend the morphological functionality of GaN nanorods by including doping and may also provide an appropriate foundation for the design of nanostructure-based electronic or photonic devices.

    DOI: 10.1002/pssb.201600722

  206. Decomposition of trimethylgallium and adduct formation in a metalorganic vapor phase epitaxy reactor analyzed by high-resolution gas monitoring system 査読有り

    Kentaro Nagamatsu, Shugo Nitta, Zheng Ye, Hirofumi Nagao, Shinichi Miki, Yoshio Honda, and Hiroshi Amano

    Phys. Status Solidi B   254 巻 ( 8 ) 頁: 1600737/1-4   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssb.201600737

  207. Effect of dislocations on the growth of p-type GaN and on the characteristics of p-n diodes

    Usami Shigeyoshi, Miyagoshi Ryosuke, Tanaka Atsushi, Nagamatsu Kentaro, Kushimoto Maki, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   214 巻 ( 8 )   2017年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physica Status Solidi (A) Applications and Materials Science  

    We investigate the influence of crystal defects on p-type GaN grown by metalorganic vapor phase epitaxy. Sets of p-type GaN films were grown on sapphire substrates and on free-standing GaN (F-GaN) substrates simultaneously using various Et-Cp2Mg flow rates. Although there is a difference of two orders of magnitude between the threading dislocation densities of p-type GaN grown on sapphire and F-GaN substrates, there is no significant difference in hole concentration. However, there are problems with the surface morphology of p-type GaN grown on sapphire. The deterioration of the surface was caused by the difference in nanopipe density. The electrical properties of a p–n junction diode formed on sapphire with a high density of nanopipes were observed using emission microscopy under both forward- and reverse-bias conditions. Our results demonstrate that the nanopipes are electrically inactive, and that other types of threading dislocation have more influence on the current–voltage characteristics.

    DOI: 10.1002/pssa.201600837

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  208. Role of threading dislocations in strain relaxation during GaInN growth monitored by real-time X-ray reflectivity 査読有り

    Guangxu Ju, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano

    Applied Physics Letters   110 巻 ( 26 ) 頁: 262105/1-5   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.4990687

  209. A-plane GaN growth on (11-20) 4H-SiC substrate with an ultrathin interlayer 査読有り

    Zheng Sun, Peifeng Song, Shugo Nitta, Yoshio Honda, Hiroshi Amano

    Journal of Crystal Growth   468 巻   頁: 866-869   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2017.01.31

  210. Selective-area growth of vertically oriented GaN nanostructures with a hafnium pre-orienting layer 査読有り

    S.-Y.Bae, K. Lekhal, H.-J.Lee, T.Mitsunari, J.-W.Min, D.-S.Leed, M.Kushimoto, Y.Honda, H.Amano

    Journal of Crystal Growth   468 巻   頁: 110-113   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2016.10.032

  211. Orientation-controlled epitaxial lateral overgrowth of semipolar GaN on Si(001) with a directionally sputtered AlN buffer layer 査読有り

    Ho-Jun Lee, Si-Young Bae, Kaddour Lekhal, Akira Tamura, Takafumi Suzuki, Maki Kushimoto, Yoshio Honda, and Hiroshi Amano

    Journal of Crystal Growth   468 巻   頁: 547-551   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jcrysgro.2016.11.116

  212. Effect of V/III ratio on the surface morphology and electrical properties of m–plane ( 101¯0 ) GaN homoepitaxial layers 査読有り

      468 巻   頁: 552-556   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have investigated the effect of V/III ratio on the surface morphology, impurity concentration and electrical properties of m–plane (101¯0) Gallium Nitride (GaN) homoepitaxial layers. Four-sided pyramidal hillocks are observed on the nominally on-axis m–plane GaN films. Hillocks sizes relatively increase by increasing the V/III ratio. All facets of pyramidal hillocks exhibit well-defined step-terrace features. Secondary ion mass spectrometry depth profiles reveal that carbon impurities decrease by increasing the V/III ratio while the lowest oxygen content is found at an optimized V/III ratio of 900. Vertical Schottky barrier diodes fabricated on the m–GaN samples were characterized. Low leakage current densities of the order of 10−10 A/cm2 at −5 V are obtained at the optimum V/III ratio. Oxygen impurities and screw-component dislocations around hillocks are found to have more detrimental impact on the leakage current mechanism.

    DOI: 10.1016/j.jcrysgro.2016.12.012

  213. Annealing effect on threading dislocations in a GaN grown on Si substrate 査読有り

      468 巻   頁: 835-838   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Effect of rapid thermal annealing (RTA) on crystal defects in a GaN layer grown on a (111)Si substrate was investigated by photoluminescence (PL) and transmission electron microscopy (TEM) analyses. The PL spectra suggested that the density of gallium vacancy is not changed by the heat treatment up to 700 °C. In the TEM specimen, we had dislocation half loops generated by off-axis propagation of the threading dislocation. We found that the half-loop of c-type dislocation shrinks/moves by a repetitive RTA at 600–700 °C. In contrast, we could find no remarkable changes in the a-type or a+c-type dislocations.

    DOI: 10.1016/j.jcrysgro.2017.01.001

  214. A-plane GaN growth on (11-20) 4H-SiC substrate with an ultrathin interlayer

    Sun Zheng, Song Peifeng, Nitta Shugo, Honda Yoshio, Amano Hiroshi

    JOURNAL OF CRYSTAL GROWTH   468 巻   頁: 866 - 869   2017年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Crystal Growth  

    A-plane GaN was attempted to be grown on (11-20) 4H-SiC bulk substrate without using a traditional thick buffer layer. By inducing TMAl treatment before the GaN growth step and using both a low pressure and V/III ratio, the interlayer thickness of the a-plane GaN/SiC was reduced to 1.7+0.5 nm. The ultrathin interlayer was observed to be either AlN or AlGaN with a low Ga composition. This study is aimed to contribute to the understanding of GaN growth on the sidewalls of c-plane trench structure SiC. The ultrathin growth technique is also hoped to be applied to the fabrication of GaN-based vertical structure nonpolar optical or electrical devices.

    DOI: 10.1016/j.jcrysgro.2017.01.031

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  215. Uneven AlGaN multiple quantum well for deep-ultraviolet LEDs grown on macrosteps and impact on electroluminescence spectral output 査読有り

    Michiko Kaneda, Cyril Pernot, Yosuke Nagasawa, Akira Hirano, Masamichi Ippommatsu, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki

    Japanese Journal of Applied Physics   56 巻   頁: 061002   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/JJAP.56.061002

  216. III-nitride core-shell nanorod array on quartz substrates

    Bae Si-Young, Min Jung-Wook, Hwang Hyeong-Yong, Lekhal Kaddour, Lee Ho-Jun, Jho Young-Dahl, Lee Dong-Seon, Lee Yong-Tak, Ikarashi Nobuyuki, Honda Yoshio, Amano Hiroshi

    SCIENTIFIC REPORTS   7 巻   頁: 45345   2017年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    DOI: 10.1038/srep45345

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    PubMed

  217. Relationship between lattice relaxation and electrical properties in polarization doping of graded AlGaN with high AlN mole fraction on AlGaN template

    Yasuda Toshiki, Takeuchi Tetsuya, Iwaya Motoaki, Kamiyama Satoshi, Akasaki Isamu, Amano Hiroshi

    APPLIED PHYSICS EXPRESS   10 巻 ( 2 )   2017年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/APEX.10.025502

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  218. Relationship between lattice relaxation and electrical properties in polarization doping of graded AlGaN with high AlN mole fraction on AlGaN template 査読有り

    Toshiki Yasuda, Tetsuya Takeuchi, Motoaki Iwaya, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano

    Applied Physics Express   10 巻   頁: 025502   2017年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: https://doi.org/10.4567/APEX.10.025502

  219. From the dawn of gan-based light-emitting devices to the present day

    Amano H.

    Handbook of Solid-State Lighting and LEDs     頁: 3-12   2017年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1201/9781315151595

    Scopus

  220. High quality Al0.99Ga0.01N layers on sapphire substrates grown at 1150 degrees C by metalorganic vapor phase epitaxy

    Katsuno Shota, Yasuda Toshiki, Hagiwara Koudai, Koide Norikatsu, Iwaya Motoaki, Takeuchi Tetsuya, Kamiyama Satoshi, Akasaki Isamu, Amano Hiroshi

    JAPANESE JOURNAL OF APPLIED PHYSICS   56 巻 ( 1 )   2017年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7567/JJAP.56.015504

    Web of Science

  221. Reduction of Dislocations in GaN on Silicon Substrate Using In Situ Etching 査読有り

    Koji Matsumoto, Toshiaki Ono, Yoshio Honda, Tetsuya Yamamoto, Shigeyoshi Usami, Maki Kushimoto, Satoshi Murakami, and Hiroshi Amano

    Physica Status Solidi b   253 巻   頁: 1700387(1-7)   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A gallium nitride (GaN) epitaxial layer with a low density of threading dislocations is successfully grown on a silicon substrate by using in situ gas
    etching. Silicon nitride (SiNx) film is used as a mask, and ammonia is intermittently supplied in hydrogen ambient during the etching. After etching,
    high-density deep pits appeared on the surface of a GaN template layer and corresponded to the threading dislocations in the layer. In this novel method,
    before growing an additional GaN layer on the template GaN layer, a second SiNx layer is deposited after the etching process, and this layer prevents GaN nuclei from growing on the upper side-walls of the pits. By using this method, the density of threading dislocations of the GaN surface is reduced to 6.7E7 cm2. This method is cost effective, completing all the necessary processes in one growth run without taking samples out from a metalorganic chemical vapor deposition (MOCVD) reactor.

    DOI: 10.1002/pssb.201700387

  222. Development of Sustainable Smart Society based on Transformative Electronics

    Ogura M., Ando Y., Usami S., Nagamatsu K., Kushimoto M., Deki M., Tanaka A., Nitta S., Honda Y., Pristovsek M., Kawai H., Yagi S., Amano H.

    2017 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM)     頁: .   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  223. Progress and Prospect of Growth of Wide-Band-Gap Group III Nitrides

    Amano Hiroshi

    III-NITRIDE BASED LIGHT EMITTING DIODES AND APPLICATIONS, 2ND EDITION   133 巻   頁: 1 - 9   2017年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Topics in Applied Physics  

    DOI: 10.1007/978-981-10-3755-9_1

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  224. From the Dawn of GaN-Based Light-Emitting Devices to the Present Day

    Amano Hiroshi

    HANDBOOK OF SOLID-STATE LIGHTING AND LEDS     頁: 3-11   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  225. High quality Al0.99Ga0.01N layers on sapphire substrates grown at 1150 °C by metalorganic vapor phase epitaxy 査読有り

    Shota Katsuno, Toshiki Yasuda, Koudai Hagiwara, Norikatsu Koide, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, and Hiroshi Amano

    Japanese Journal of Applied Physics   56 巻   頁: 015504   2016年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: https://doi.org/10.7567/JJAP.56.015504

  226. Improved crystal quality of semipolar (10(1)over-bar3) GaN on Si(001) substrates using AlN/GaN superlattice interlayer 査読有り

    Ho-Jun Lee, Si-Young Bae, Kaddour Lekhal, Tadashi Mitsunaria, Akira Tamura, Yoshio Honda, Hiroshi Amano

    Journal of Crystal Growth   454 巻   頁: 114-120   2016年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: https://doi.org/10.1016/j.jcrysgro.2016.09.004

  227. Controlled morphology of regular GaN microrod arrays by selective area growth with HVPE 査読有り

    Kaddour Lekhal, Si-Young Bae, Ho-Jun Lee, Tadashi Mitsunari, Akira Tamura, Manato Deki, Yoshio Honda, Hiroshi Amano

    Journal of Crystal Growth   447 巻   頁: 55-61   2016年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The selective area growth (SAG) of GaN was implemented on patterned GaN/sapphire templates by hydride vapor phase epitaxy (HVPE) to fabricate regular arrays of Ga-polar GaN microrods. The control of growth parameters such as H2/N2 carrier gas ratio, growth temperature, and absolute NH3/HCl gas flow resulted in changes in the growth morphology.

    DOI: 10.1016/j.jcrysgro.2016.05.008

  228. Development of highly durable deep-ultraviolet AlGaN-based LED multichip array with hemispherical encapsulated structures using a selected resin through a detailed feasibility study 査読有り

    Shoko Nagai, Kiho Yamada, Akira Hirano, Masamichi Ippommatsu, Masahiro Ito, Naoki Morishima, Ko Aosaki, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki

    Japanese Journal of Applied Physics   55 巻   頁: 082101/1-7   2016年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: http://doi.org/10.7567/JJAP.55.082101

  229. Deep level study of Mg-doped GaN using deep level transient spectroscopy and minority carrier transient spectroscopy 査読有り

    Tran Thien Duc, Galia Pozina, Hiroshi Amano, Bo Monemar, Erik Janz´en, and Carl Hemmingsson

    PHYSICAL REVIEW   B94 巻   頁: 045206/1-8   2016年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Deep levels in Mg-doped GaN grown by metal organic chemical vapor deposition, undoped GaN grown by MOCVD, and halide vapor phase epitaxy-grown GaN have been studied using deep level transient spectroscopy and minority charge carrier transient spectroscopy.

    DOI: 10.1103/PhysRevB.94.045206

  230. Study of radiation detection properties of GaN pn diode 査読有り

    Mutsuhito Sugiura, Maki Kushimoto, Tadashi Mitsunari, Kohei Yamashita, Yoshio Honda, Hiroshi Amano, Yoku Inoue, Hidenori Mimura, Toru Aoki, and Takayuki Nakano

    Japanese Journal of Applied Physics   55 巻   頁: 05FJ02/1-3   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Recently, GaN, which has remarkable properties as a material for optical devices and high power electron devices, has also attracted attention as a material for radiation detectors. We previously suggested the use of BGaN as a neutron detector material. However, the radiation detection characteristics of GaN itself are not yet adequately understood. For realizing a BGaN neutron detector, the understanding of the radiation detection characteristics of GaN, which is a base material of the neutron detector, is important. In this study, we evaluated the radiation detection characteristics of GaN. We performed I V and energy spectrum measurements under alpha ray, gamma ray, and thermal neutron irradiations to characterize the radiation detection characteristics of a GaN diode. The obtained results indicate that GaN is an effective material for our proposed new BGaN-based neutron detector.

  231. Low-ohmic-contact-resistance V-based electrode for n-type AlGaN with high AlN molar fraction 査読有り

    Kazuki Mori, Kunihiro Takeda, Toshiki Kusafuka, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano

    Low-ohmic-contact-resistance V-based electrode for n-type AlGaN with high AlN molar fraction   55 巻 ( 5S ) 頁: 05FL03/1-5   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  232. Observation of relaxation time of surface charge limit for InGaN photocathodes with negative electron affinity 査読有り

    Daiki Sato, Tomohiro Nishitani, Yoshio Honda and Hiroshi Amano

    Japanese Journal of Applied Physics   55 巻 ( 5S ) 頁: 05FH05/1-4   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  233. Emission Characteristics of InGaN/GaN Core-Shell Nanorods Embedded in a 3D Light-Emitting Diode 査読有り

    Byung Oh Jung, Si-Young Bae, Seunga Lee, Sang Yun Kim, Jeong Yong Lee, Yoshio Honda and Hiroshi Amano

    Nanoscale Research Letters   11 巻   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report the selective-area growth of a gallium nitride (GaN)-nanorod-based InGaN/GaN multiple-quantum-well (MQW) core-shell structure embedded in a three-dimensional (3D) light-emitting diode (LED) grown by metalorganic chemical vapor deposition (MOCVD) and its optical analysis. High-resolution transmission electron microscopy (HR-TEM) observation revealed the high quality of the GaN nanorods and the position dependence of the structural properties of the InGaN/GaN MQWs on multiple facets. The excitation and temperature dependences of photoluminescence (PL) revealed the m-plane emission behaviors of the InGaN/GaN core-shell nanorods. The electroluminescence (EL) of the InGaN/GaN core-shell-nanorod-embedded 3D LED changed color from green to blue with increasing injection current. This phenomenon was mainly due to the energy gradient and deep localization of the indium in the selectively grown InGaN/GaN core-shell MQWs on the 3D architecture.

    DOI: 10.1186/s11671-016-1441-6

  234. Preflow trimethylaluminum treatment effect on GaN growth on SiC with an ultrathin interlayer 査読有り

    Zheng Sun, Kentaro Nagamatsu, Marc Olsson, Peifeng Song, Manato Deki, Shugo Nitta, Yoshio Honda and Hiroshi Amano

    Japanese Journal of Applied Physics,   55 巻 ( 5S ) 頁: 05FB06/1-5   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  235. Growth of semipolar (1-101) high-indium-content InGaN quantum well using InGaN tilting layer on Si(001) 査読有り

    Maki Kushimoto, Yoshio Honda and Hiroshi Amano

    Japanese Journal of Applied Physics   55 巻 ( 5S ) 頁: 05FA10/1-4   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  236. Evaluation of excess In during metal organic vapor-phase epitaxy growth of InGaN by monitoring via in situ laser scattering 査読有り

    Tetsuya Yamamoto, Akira Tamura, Shigeyoshi Usami, Tadashi Mitsunari, Kentaro Nagamatsu, Shugo Nitta, Yoshio Honda and Hiroshi Amano

    Japanese Journal of Applied Physics   55 巻 ( 5S ) 頁: 05FD03/1-4   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Using an in situ laser absorption and scattering method, the surface roughness and incorporation of In in InGaN layers grown by metal organic vapor-phase epitaxy (MOVPE) were monitored.

  237. Development of GaN-based blue LEDs and metalorganic vapor phase epitaxy of GaN and related materials 招待有り

    Hiroshi Amano

    Progress in Crystal Growth and Characterization of Materials   62 巻   頁: 126–135   2016年4月

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    担当区分:筆頭著者   記述言語:英語  

    DOI: https://doi.org/10.1016/j.pcrysgrow.2016.04.006

  238. Structural and optical study of core–shell InGaN layers of nanorod arrays with multiple stacks of InGaN/GaN superlattices for absorption of longer solar spectrum 査読有り

      55 巻 ( 5S ) 頁: 05FG03/1-8   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the material and optical properties of core–shell InGaN layers grown on GaN nanorod arrays. The core–shell InGaN layers were well grown on polarization-reduced surfaces such as semipolar pyramids and nonpolar sidewalls. In addition, to compensate the biaxial strain between GaN and InGaN layers, we grew interlayers underneath a thick InGaN layer. Here, the interlayers were composed of multiple superlattice structures. We could observe that the indium composition of core–shell InGaN structures increased with the number of interlayers. This indicates that the absorption energy band of InGaN alloys can be better matched to the spectral irradiance of the solar spectrum in nature. We also implemented a simulation of Ga-polar and nonpolar InGaN-based solar cells based on the indium composition obtained from the experiments. The result showed that nonpolar InGaN solar cells had a much higher efficiency than Ga-polar InGaN solar cells with the same thickness of the absorption layer.

  239. Selective-area growth of GaN microrods on strain-induced templates by hydride vapor phase epitaxy 査読有り

    Kaddour Lekhal, Si-Young Bae, Ho-Jun Lee, Tadashi Mitsunari, Akira Tamura, Manato Deki, Yoshio Honda and Hiroshi Amano

    Japanese Journal of Applied Physics   55 巻   頁: 05FF03/1-5   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  240. Theoretical approach to surface reconstruction of InN(0001) during raised-pressure metalorganic vapor-phase epitaxy 査読有り

    Akira Kusaba, Yoshihiro Kangawa, Yoshio Honda, Hiroshi Amano and Koichi Kakimoto

    Japanese Journal of Applied Physics   55 巻 ( 5S ) 頁: 05FM01/1-4   2016年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  241. Study of enhanced photovoltaic behavior in InGaN-based solar cells by using SiNx insertion layer: Influence of dislocations 査読有り

    Seunga Lee, Yoshio Honda, Hiroshi Amano, Jongjin Jang and Okhyun Nam

    Japanese Journal of Applied Physics Rapid Communications   55 巻 ( 3 ) 頁: 030306/1-4   2016年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Using a SiN insertion layer to reduce dislocations, enhanced photovoltaic properties could be obtained in pin InGaN GaN heterojunction solar cell. To investigate the influence of the dislocations on the photovoltaic behaviors, a sample grown without SiN insertion layer was identically prepared for comparison. From optical properties measurements, the reduction in the number of non-radiative centers and a stronger In localization effect was shown in the sample with SiN insertion layer. However, the quantum confined stark effect was almost negligible in both the samples.

  242. Effect of piezoelectric field on carrier dynamics in InGaN-based solar cells 査読有り

    Lee, Seunga; Honda, Yoshio; Amano, Hiroshi

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   49 巻 ( 2 ) 頁: 025103   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To understand the effect of piezoelectric fields on carrier dynamics, we numerically investigated a simple p-GaN/i-InxGa1-xN/n-GaN solar cell structure. A reliable simulation model was obtained by comparing the experimental and simulated results in advance.

  243. Highly elongated vertical GaN nanorod arrays on Si substrates with an AlN seed layer by pulsed-mode metal-organic vapor deposition 査読有り

    Si-Young Bae, Byung Oh Jung, Kaddour Lekhal, Sang Yun Kim, Jeong Yong Lee, Dong-Seon Lee, Manato Deki, Yoshio Honda and Hiroshi Amano

    CrystEngComm   18 巻   頁: 1505-1514   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    . Unlike the thick and high (or middle)-quality GaN templates normally used, nanorod growth was performed on an ultrathin and low-quality AlN/Si platform. Using kinetically controlled growth conditions and a patterning process, exceptionally long GaN nanorods were achieved with high geometric precision.

    DOI: 10.1039/C5CE02056E

  244. The interface analysis of GaN grown on 0° off 6H-SiC with an ultra-thin buffer layer 査読有り

    Zheng Sun, Akio Ohta, Seiichi Miyazaki, Kentaro Nagamatsu, Hojun Lee, Marc Olsson, Zheng Ye, Manato Deki, Yoshio Honda, and Hiroshi Amano

    Japanese Journal of Applied Physics   55 巻   頁: 010303/1-3   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Previously, we reported a growth method by MOVPE using a single two-dimensional growth step, resulting in 1.2-micron thick crack-free GaN directly grown on 6H-SiC substrate. The introduction of Al-treatment prior to the standard GaN growth step resulted in improved surface wetting of gallium on the SiC substrate.

  245. Growth of GaN on sapphire via low-temperature deposited buffer layer and realization of p-type GaN by Mg doping followed by low-energy electron beam irradiation 招待有り 査読有り

    Hiroshi Amano

    Rev. Mod. Phys.   87 巻 ( 4 ) 頁: 1133-1138   2015年12月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This is a personal history of one of the Japanese researchers engaged in developing a method for
    growing GaN on a sapphire substrate, paving the way for the realization of smart television and
    display systems using blue LEDs. The most important work was done in the mid to late 1980s. The
    background to the author's work and the process by which the technology enabling the growth of
    GaN and the realization of p-type GaN was established are reviewed.

  246. Single-crystalline semipolar GaN on Si(001) using a directional sputtered AlN intermediate layer 査読有り

    Tadashi Mitsunari, Ho Jun Lee, Yoshio Honda, Hiroshi Amano

    Journal of Crystal Growth   431 巻   頁: 60-63   2015年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We obtained single-crystalline semipolar (10View the MathML source1¯3)GaN on a nominal Si(001) substrate with sputtered AlN using the directional feature of sputtering.

    DOI: 10.1016/j.jcrysgro.2015.08.027

  247. Time-resolved photoluminescence properties of hybrids based on inorganic AlGaN/GaN quantum wells and colloidal ZnO nanocrystals 査読有り

    M. Forsberg, C. Hemmingsson, H. Amano, G. Pozina

    Superlattices and Microstructures   87 巻   頁: 38-41   2015年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Dynamic properties are studied for the AlGaN/GaN quantum well (QW) structures with and without the coating of colloidal ZnO nanocrystals (NCs). The QW exciton recombination rate was reduced in such hybrids compared to the bare QW structure only in the sample with the thinnest cap layer of 3 nm. Assuming that one of the recombination mechanisms in this hybrid is non-radiative resonant energy transfer (NRET) between the QW and the energy acceptor material i.e. ZnO NCs, the maximum pumping efficiency was estimated to be 0.42 at 60 K. The NRET effect is, however, vanished after several months despite that the hybrid structures are composed of chemically stable components.

    DOI: doi:10.1016/j.spmi.2015.07.017

  248. Polarization dilution in a Ga-polar UV-LED to reduce the influence of polarization charges 査読有り

    Toshikiu Yasuda, Kento Hayashi, Syouta Katsuno, Tetsuya Takeuchi, Satoshi Kamiyama, Motoaki Iwaya, Isamu Akasaki, and Hiroshi Amano

    Physica Status Solidi a   212 巻 ( 5 ) 頁: 920-924   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated the influence of polarization charges in nitride-based semiconductors.

    DOI: 10.1002/pssa.201431730

  249. Excitation density dependence of radiative and nonradiative recombination lifetimes in InGaN/GaN multiple quantum wells 査読有り

    Hideaki Murotani, Yoichi Yamada, Yoshio Honda, and Hiroshi Amano

    Physica Status Solidi b   252 巻 ( 5 ) 頁: 940-945   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The optical properties of InGaN/GaN multiple quantum wells (MQWs) have been studied by means of photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopy.

    DOI: 10.1002/pssb.201451491

  250. Resonant Raman and FTIR spectra of carbon doped GaN 査読有り

    S. Ito, H. Kobayashi, K. Arak,i, K. Suzuki, N. Sawaki, K. Yamashita, Y. HOnda, H. Amano

    Journal of Crystal Grwoth   414 巻 ( 15 ) 頁: 56-60   2015年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: doi:10.1016/j.jcrysgro.2014.11.024

  251. Electrical characteristics of a-plane low-Mg-doped p-GaN Schottky contacts 査読有り

    Moe Naganawa, Toshichika Aoki, Ji-Su Son, Hiroshi Amano, Kenji Shiojima

    physica status solidi (b)   252 巻 ( 5 ) 頁: 1024–1030   2015年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electrical characteristics of a variety of Schottky contacts formed with ten metal species on the a-plane of p-type low-Mg-doped GaN grown on r-plane sapphire substrates were studied.

    DOI: 10.1002/pssb.201451581

  252. Optically pumped lasing properties of (1-101) InGaN/GaN stripe multi quantum wells with ridge cavity structure on patterned (001) Si substrates 査読有り

    Maki Kushimoto, Tomoyuki Tanikawa, Yoshio Honda and Hiroshi Amano

    Applied Physics Express   8 巻 ( 2 ) 頁: 022702   2015年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We demonstrated lasing action and investigated the optical properties of (1 (1) over bar 01) multiquantum-well (MQW) stripe crystals on patterned (001) Si substrates. Longitudinal and higher order transverse modes were observed from a ridge waveguide structure. These results strongly suggest the possibility of fabricating (1 (1) over bar 01) InGaN MQW laser diodes on (001) Si. (C) 2015 The Japan Society of Applied Physics

    DOI: doi:10.7567/APEX.8.022702

  253. Dynamic properties of excitons in ZnO/AlGaN/GaN hybrid nanostructures 査読有り

    Mathias Forsberg, Carl Hemmingsson, Hiroshi Amano , Galia Pozina

    Scientific Reports   5 巻   頁: 7889   2015年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    III-nitride semiconductor/organic polymer hybrid heterostructures combine advantages of epitaxially grown semiconductor quantum wells (QW) with inexpensive polymers having efficient luminescence in the visible region1. Such hybrid micro-structured light emitting diodes (LED) are promising for fabrication of low-cost and highly efficient microlight sources that can be used in full-color displays, imaging systems, miniature chemical and biological sensors. In typical polyfluorene/GaN-based LED hybrids, UV emission from a GaN heterostructure down converts to the organic polymer fluorescence in the visible region via a radiative energy transfer. Overlapping between the UV luminescence and the polyfluorene absorption is required for the operation
    of these hybrids. Today, a novel class of hybrid structures is suggested, in which a non-radiative resonant energy transfer (NRET) from excitation generated in inorganic QWs to excitons in organic films can be utilized. Such LEDs might be considerably more efficient than their radiative energy transfer analogues. In addition to the necessity of a significant spectral overlap between the QW emission and the polymer absorption spectrum, these devices require that the two materials are placed in a close interaction distance of a few nm. The bottleneck is that the operation lifetime of organic/semiconductor hybrid LED structures is limited by degradation
    of polyfluorenes. Using colloidal semiconductor nanocrystals (NCs) instead of polymers can significantly improve the lifetime of such devices. In addition to superior luminescence properties, relatively low cost and chemical stability, the spectral tunability can be achieved by changing the particle chemistry and size. The efficiency of non-radiative resonance energy transfer is typically determined using transient photoluminescence
    (PL) measurements from the quenching of the QW exciton lifetime in the presence of acceptor material (i.e.
    colloidal NCs or polyfluorene). It might be correct in assumption that NRET is the only additional recombination channel appearing in hybrids compared to the bareQWstructure. However, other factors can play also a significant role. For example, surface potential effects have to be considered when non-radiative resonant energy transfer is measured using dynamic properties of the QW excitons.
    Thus, in this work we have studied and discussed the possibility of NRET in hybrid structures fabricated using ZnO NCs films coated on the top of the AlGaN/GaN QWs samples. ZnO NCs satisfies the requirement of
    absorption overlapping with GaN emission (a room temperature band gap energy is 3.3 and 3.4 eV for ZnO and GaN, respectively). Dynamic properties ofQWexcitons in the hybrids and in the bareQWsamples are analyzed in dependence on the QWs cap layer thickness.

    DOI: doi:10.1038/srep07889

  254. Development of underfilling and encapsulation for deep-ultraviolet LEDs 査読有り

    Kiho Yamada, Yuuta Furusawa, Shoko Nagai, Akira Hirano, Masamichi Ippommatsu, Ko Aosaki, Naoki Morishima, Hiroshi Amano and Isamu Akasaki

    Applied Physics Express   8 巻 ( 1 ) 頁: 012101   2015年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  



    The currently available resins for underfilling and encapsulation are limited to wavelengths longer than approximately 330 nm because almost all resins are decomposed by deep-ultraviolet light. Fluorine resins are possible materials for underfilling and encapsulation in deep-ultraviolet LEDs, and we have investigated methods of underfilling and encapsulation using such resins. Also, their durability at wavelengths of 265 and 285 nm has been studied from the photochemical viewpoint, and we propose a stable amorphous fluorine resin that is optically isotropic. Also, a trial of encapsulation using the resin has been made.

    DOI: doi:10.7567/APEX.8.012101

  255. Highly ordered catalyst-free InGaN/GaN core-shell architecture arrays with expanded active area region 査読有り

    Jung, Byung Oh; Bae Si-Young; Kim, Sang Yun; Lee, Seunga; Lee, Jeong Yong; Lee, Dong-Seon; Kato, Yoshihiro; Honda, Yoshio ;Amano, Hiroshi

    Nano Energy   11 巻   頁: 294-303   2015年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Highly ordered, position-controlled gallium nitride (GaN) nanowire based multiple-quantum-wells (MQWs) core-shell architecture arrays are synthesized by metalorganic chemical vapor deposition (MOCVD). We investigate the possibility of using GaN nanowire arrays as a basal template for the growth of InxGa1-xN/GaN MQWs. The MQWs on three different crystal facets (c(-), m(-), and semipolar-plane) of GaN nanowire exhibit dissimilar structural properties. The structural characteristics of InGaN/GaN core-shell arrays are inspected by cross-sectional high-resolution transmission electron microscopy (HR-TEM). We also investigate the optical properties of MQW core-shell structure nanoarrays. The luminescent characteristics of InGaN/GaN core-shell structure arrays are determined by photoluminescence (PL) and cathodoluminescence (CL) measurements. The monochromatic CL images clearly show the light emission behavior of InGaN/GaN MQW coaxial structure. Two distinguishable light emission peaks were observed in the GaN nanowire based core-shell structure. The characteristic of light emission mainly depends on the properties of MQWs, which are generated from different crystal facets of GaN. In addition, the light emission intensity shows different behaviors depending on the area of the GaN nanowire m-plane. The results of this study suggest that GaN nanowire arrays can be used as a good alternative basal template for next-generation light-emitting diodes (LEDs).

    DOI: DOI: 10.1016/j.nanoen.2014.11.003

  256. Continuous in situ X-ray reflectivity investigation on epitaxial growth of InGaN by metalorganic vapor phase epitaxy 査読有り

    Guangxu Ju, Shingo Fuchi, Masao Tabuchi, Hiroshi Amano, Isamu Akasaki

    Journal of Crystal Growth   407 巻   頁: 68-73   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Continuous in situ X-rayreflectivity(XRR)measurementswereusedtoinvestigatethegrowthprocessof
    an In0.11Ga0.89N epilayeranditssinglequantumwellgrownonc-planeGaN/sapphiretemplatesusingan
    in-house-designed metalorganicvaporphaseepitaxyinstalledinalaboratory-gradeX-raydiffract-
    ometer.Thesurfacerougheningoftheepilayerasafunctionofgrowthtimewascalculatedfromthe
    continuous in situ XRR curve.Thegrowthrate,criticalthickness hc(r) for surfaceroughening,and
    roughening ratewereobtained.Theexperimentalcriticalthickness hc(r) of theIn0.11Ga0.89N epilayer
    analyzed fromthecontinuous in situ XRR curvewas14.870.4 nm.Basedonthecalculatedtheoretical
    critical thickness hc and theexperimental hc(r,2), Fischer's modelseemstobeappropriatefordescribing
    the criticalthicknessoftheInGaN/GaN.

    DOI: 10.1016/j.jcrysgro.2014.08.023

  257. Photoemission lifetime of a negative electron affinity gallium nitride photocathode 査読有り

    Tomohiro Nishitani, Masao Tabuchi, Hiroshi Amano, Takuya Maekawa, Makoto Kuwahara and Takashi Meguro

    Journal of Vacuum Science and Technology   B32 巻 ( 6 ) 頁: 06F901   2014年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A photocathode electron source using p-type GaN semiconductor with a negative electron affinity (NEA) surface has been studied for its ability to maintain an extended NEA state. The key technology of NEA photocathodes is the formation of electric dipoles by cesium and gallium atoms on the surface, which makes it possible for photoexcited electrons in the conduction band minimum to escape into the vacuum. This means that in order to keep the electron energy spread as small as possible, the excitation photon energy should be tuned to the band gap energy. However, the NEA surface is damaged by the adsorption of residual gas and the back-bombardment of ionized residual gas by photoelectrons. The p-type GaN semiconductor was measured time evolution in quantum yield during NEA surface activation, and a lifetime of quantum yield of excitation energy corresponding to the band gap energy in comparison to the p-type GaAs as the conventional NEA photocathode. In NEA surface activation process, the quantum yield of the GaN was more than 3 orders of magnitude higher than that of the GaAs by only cesium deposition. The exposure amount of cesium in the NEA surface activation of the GaAs was 1.5 times as that of the GaN, even though the quantum yield of the GaAs was the same value as the GaN. Lifetime of NEA-photocathodes using the GaN was 21 times longer than that using the GaAs. The decrease of quantum yield of the GaAs was well correlated in the form of the exponential decrease function with a decrease time of 4.4 h, while the decrease of quantum yield of the GaN was well correlated in the form of the exponential decrease function with two decrease times of 47 and 174 h.

  258. Nature of yellow luminescence band in GaN grown on Si substrate 査読有り

    Shogo Ito, Taihei Nakagita, Nobuhiko Sawaki, Hyung Soo Ahn, Masashi Irie, Toshiki Hikosaka, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano

    Japanese Journal of Applied Physics   53 巻   頁: 11RC02/1-5   2014年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: doi:10.7567/JJAP.53.11RC02

  259. Atom probe tomography study of Mg-doped GaN layers 査読有り

    S Khromov, D Gregorius, R Schiller, J Lösch, M Wahl, M Kopnarski, H Amano, B Monemar, L Hultman and G Pozina

    Nanotechnology   25 巻 ( 27 )   2014年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: doi:10.1088/0957-4484/25/27/275701

  260. Characterization of nonpolar a-plane InGaN/GaN multiple quantum well 査読有り

    Ji-Su Son, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano

    Japanese Journal of Applied Physics   53 巻   頁: 05FL01   2014年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The characteristics of nonpolar a-plane (1120) GaN (a-GaN) grown using single and double nanopillar SiO2 masks were investigated. The two
    nanopillar SiO2 masks were directly fabricated on an r-plane sapphire substrate and a-GaN by the epitaxial lateral overgrowth (ELOG) technique.
    Through the use of the single and double nanopillar SiO2 masks, the crystalline quality and optical properties of a-GaN were markedly improved
    because of the nanoscale ELOG effect and a number of voids in the single and double nanopillar SiO2 mask areas in comparison with the planar
    sample. The submicron pit densities of the planar, single, and double nanopillar mask samples were >2 ' e9, >7e8, and >4e8cm-2,
    respectively. The internal quantum efficiency (IQE) values at room temperature of three-period InGaN/GaN multiple quantum wells (MQWs) grown
    using the planar, single, and double nanopillar masks were 45, 60, and 68% at a carrier concentration of 1.0e18cm-3, respectively.

    DOI: 10.7567/JJAP.53.05FL01

  261. X-ray investigations of GaInN single quantum wells grown by atomic layer epitaxy and metalorganic vapor phase epitaxy 査読有り

    Guangxu Ju, Yoshihiro Kato, Yoshio Honda, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano

    physica status solidi (c)   11 巻 ( 3-4 ) 頁: 393-396   2014年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A set of GaN/GaInN single quantum wells (SQWs) were grown on c-plane GaN/sapphire templates using metal organic vapor phase epitaxy (MOVPE) and atomic layer epitaxy (ALE). The structural information on the interfaces and surfaces was obtained by fitting the experimental X-ray spectra and was compared between MOVPE and ALE mode. The X-ray crystal truncation rod (CTR) scattering measurement results showed that the samples grown by ALE had sharper interfaces than those grown by MOVPE. Both the X-ray reflectivity (XRR) curve-fitting results and atomic force microscope (AFM) results indicated that the surfaces of the ALE-grown SQWs were smoother than those of MOVPE-grown SQWs.

    DOI: 10.1002/pssc.201300670

  262. Enhancement of light output power on GaN based light emitting diodes using two direction stripe patterned sapphire substrate 査読有り

    Okuno, Koji; Oshio, Takahide; Shibata, Naoki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    Physica Status Solidi C   11 巻   頁: 722-725   2014年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To achieve both the reduction of threading dislocation density (TDD) and the enhancement of light extraction efficiency (LEE) of light-emitting diodes (LEDs), a two-directional stripe-patterned sapphire substrate (TPSS) was fabricated. First, a stripe pattern parallel to the a-axis of Al2O3 was formed on an as-received c -sapphire wafer and then a second stripe pattern rotated around 3° from the m-axis of Al2O3 was formed on the first stripe PSS. The light output power of TPSS LEDs was around 1.25 times higher than that of LEDs on a flat sapphire substrate. This enhancement is caused by the increase of both the internal quantum efficiency (IQE) and the LEE. On the other hand, although the LED on TPSS with the second stripe just parallel to the m-axis of Al2O3 showed a similar enhancement ratio of the light output power, the current leakage of this LED increased with the concentration of threading dislocations on the surface of LEDs. Stripes rotated 3° from the m-axis of Al2O3 changed the growth mode and realized GaN films with a smooth surface without pit formation. Therefore, the misalignment of the stripe from the m-axis of Al2O3 will become a new design parameter for realizing high-efficiency reliable LEDs.

    DOI: 10.1002/pssc.201300470

  263. Epitaxial growth of GaN by REMOCVD in the downflow of a very high frequency(VHF) N2/H2 excited plasma 査読有り

    Yi Lu, Hiroki Kondo,Kenji Ishikawa,Osamu Oda,KeigoTakeda,Makoto Sekine, Hiroshi Amano,Masaru Hori

    Journal of Crystal Growth   391 巻   頁: 97-103   2014年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We found that this REMOCVD allowed the growth of epitaxial GaN films of the wurtzite structure of (0001) orientation on sapphire substrates with a high growth rate of 0.42 μm/h at a low temperature of 800 °C. The present REMOCVD is a promising method for GaN growth at relatively low temperature and without using costly ammonia gas.

    DOI: 10.1016/j.jcrysgro.2014.01.014

  264. Growth of InGaN/GaN multiple quantum wells on size-controllable nanopyramid arrays 査読有り

    Cao Miao, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano

    Japanese Journal of Applied Physics   53 巻   頁: 0303060   2014年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Regularly distributed nanopyramid arrays with a highly uniform size were grown by selective-area growth. The nanopyramid size could be tuned by varying the growth time. Two emission peaks were observed from multiple quantum wells grown on the nanopyramids. The longer-wavelength peak originated from the apexes of pyramids with threefold symmetry. High-density stacking faults observed at these triangular apexes might be responsible for the higher indium incorporation. The formation of embedded voids inside the pyramids was explained by the different growth rates at the edge and center of the mask window caused by the low diffusion length.

    DOI: 10.7567/JJAP.53.030306

  265. In situ X-ray investigation of changing barrier growth temperatures on InGaN single quantum wells in metal-organic vapor phase epitaxy 査読有り

    Guangxu Ju, Yoshio Honda, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano

    Journal of Applied Physics   115 巻   頁: 094906   2014年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The effects of GaN quantum barriers with changing growth temperatures on the interfacial
    characteristics of GaN/InGaN single quantum well (SQW) grown on GaN templates by metalorganic
    vapour phase epitaxy were in situ investigated by X-ray crystal truncation rod (CTR) scattering and
    X-ray reflectivity measurements at growth temperature using a laboratory level X-ray diffractometer.
    Comparing the curve-fitting results of X-ray CTR scattering spectra obtained at growth temperature
    with that at room temperature, the InxGa1-xN with indium composition less than 0.11 was stabile of
    the indium distribution at the interface during the whole growth processes.

    DOI: 10.1063/1.4867640

  266. Multijunction GaInN-based solar cells using a tunnel junction 査読有り

    Hironori Kurokawa, Mitsuru Kaga, Tomomi Goda, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano

    Applied Physics Express   7 巻 ( 3 ) 頁: 034104   2014年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We fabricated and characterized a two-junction GaInN-based solar cell using a tunnel junction fabricated by crystal growth. This solar cell has two active layers with a differing bandgap energy corresponding to blue or green light. We confirmed that the open-circuit voltage (VOC) in this solar cell was increased by the series connection using the tunnel junction. The short-circuit current density, VOC, fill factor, and energy conversion efficiency of this solar cell were 0.28 mA/cm2, 3.0 V, 0.5, and 0.41%, respectively, under an air mass filter of 1.5 G at 1-sun irradiation and room temperature.

    DOI: 10.7567/APEX.7.034104

  267. Novel activation process for Mg-implanted GaN 査読有り

    Shin Hashimoto, Takao Nakamura, Yoshio Honda, Hiroshi Amano

    Journal of Crystal Growth   388 巻   頁: 112-115   2014年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A novel activation process for Mg-implanted GaN was demonstrated. As opposed to the conventional thermal annealing process, an H2/NH3 alternating supply annealing process achieved better optical activation, stronger near-ultraviolet luminescence and weaker yellow luminescence in the photoluminescence spectroscopy. After this process, small hexagonal hillocks were observed on the surface, which indicated that crystal regrowth was induced by this process, consisting of decomposition of GaN by H2 supplies and re-crystallization by NH3 supplies. It was revealed that the implanted Mg could easily be located at the activation site by means of crystal regrowth by this process.

    DOI: doi:10.1016/j.jcrysgro.2013.07.011

  268. Properties of the main Mg-related acceptors in GaN from optical and structural studies 査読有り

    B. Monemar, P. P. Paskov, G. Pozina, C. Hemmingsson, J. P. Bergman, S. Khromov, V. N. Izyumskaya, V. Avrutin, X. Li, H. Morkoç, H. Amano, M. Iwaya, and I. Akasaki

    Journal of Applied Physics   115 巻   頁: 053507   2014年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The luminescent properties of Mg-doped GaN have recently received particular attention, e.g., in the
    light of new theoretical calculations, where the deep 2.9 eV luminescence band was suggested to be
    the main optical signature of the substitutional MgGa acceptor, thus, having a rather large binding
    energy and a strong phonon coupling in optical transitions. We present new experimental data on
    homoepitaxial Mg-doped layers, which together with the previous collection of data give an
    improved experimental picture of the various luminescence features in Mg-doped GaN.

    DOI: 10.1063/1.4862928

  269. Growth of low-defect-density nonpolar a-plane GaN on r-plane sapphire using pulse NH3 interrupted etching 査読有り

    Ji-Su Son, Yoshio Honda, and Hiroshi Amano

    Optics Express   22 巻 ( 3 ) 頁: 3585-3592   2014年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Nonpolar a-plane (11-20) GaN (a-GaN) layers with low overall defect density and high crystalline quality were grown on r-plane sapphire substrates using etched a-GaN. The a-GaN layer was etched by pulse NH3 interrupted etching.

    DOI: 10.1364/OE.22.003585

  270. Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique 査読有り

    Byung Oh Jung, Si-Young Bae, Yoshihiro Kato, Masataka Imura, Dong-Seon Lee, Yoshio Honda and Hiroshi Amano

    CrystEngComm   16 巻   頁: 2273-2282   2014年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    we demonstrate a scalable process for the precise position-controlled selective growth of
    GaN nanowire arrays by metalorganic chemical vapor deposition (MOCVD) using a pulsed-mode growth
    technique. The location, orientation, length, and diameter of each GaN nanowire are controlled via
    pulsed-mode growth parameters such as growth temperature and precursor injection and interruption
    durations.

    DOI: 10.1039/c3ce42266f

  271. Characteristics of a-plane GaN films grown on optimized silicon-dioxide-patterned r-plane sapphire substrates 査読有り

    Ji-Su Son, Y. Honda, M. Yamaguchi, H. Amano, K. H. Baik, Y. G. Seo and S. M. Hwang

    Thin Solid Films   546 巻 ( 11 ) 頁: 108-113   2013年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the characteristics of a-plane GaN films directly grown on optimized silicon-dioxide-patterned r-plane sapphire substrates. Various shapes and sizes of silicon dioxide patterns were considered with the aim of achieving fully coalescent a-plane GaN films with a smooth surface and high crystalline quality. The omega full widths at half maximum of the X-ray rocking curve values of optimized a-plane GaN films with regular hexagonal patterns of 1 micron window width and 6 micron mask width were measured to be 597 arcsec along the c-axis direction and 457 arcsec along the m-axis direction. Atomic force microscopy images revealed a significant reduction in the density of submicron pits in the mask region.

  272. Effects of exciton localization on internal quantum efficiency of InGaN nanowires 査読有り

    Hideaki Murotani, Yoichi Yamada, Takuya Tabata, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano

    Journal of Applied Physics   114 巻   頁: 153506   2013年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Internal quantum efficiency of InGaN nanowires grown by PA MBE was investigated in detail.

    DOI: 10.1063/1.4825124

  273. Strain-Compensated Effect on the Growth of InGaN/AlGaN Multi-Quantum Well by Metalorganic Vapor Phase Epitaxy 査読有り

    Tomohiro Doi, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JB14   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    InGaN/AlGaN multi-quantum wells (MQWs) were grown by metalorganic vapor phase epitaxy. The In composition of the InGaN well layer was found to increase with the tensile strain of the AlGaN barrier layer. The InGaN/AlGaN strain-compensated structure can be grown at a higher growth temperature than that of the InGaN/GaN MQW, which shows that the same emission wavelength and thus the density of the V-defects can be effectively suppressed.

    DOI: 10.7567/JJAP.52.08JB14

  274. GaN Overgrowth on Thermally Etched Nanoporous GaN Template 査読有り

    Cao Miao, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JB03   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A thermal-etching process for fabricating nanoporous GaN templates in a metalorganic vapor phase epitaxy (MOVPE) reactor was proposed. Such nanoporous templates exhibited nearly complete strain relaxation and considerably increased photoluminescence (PL) intensity. The threading dislocation density (TDD) after overgrowth was reduced from 3 ×109 to 4 ×108 cm-2 for the template with poor quality, whereas little improvement was observed for the high-quality template (TDD, 4 ×108 cm-2). Multiple quantum wells (MQWs) grown on a nanoporous template fabricated from the high-quality GaN template were used to assess the effect on LED performance. The PL intensity of the sample with a nanoporous structure showed a twofold increase in PL intensity compared with the control sample.

    DOI: 10.7567/JJAP.52.08JB03

  275. Growth of GaN on Si(111) Substrates via a Reactive-Sputter-Deposited AlN Intermediate Layer 査読有り

    Takaya Yamada, Tomoyuki Tanikawa, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Japanese Journal of Applied Physics   52 巻   頁: 08JB16   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    GaN films were successfully grown on Si(111) substrates using a reactive-sputter-deposited AlN intermediate layer (sp-AlN) at 350 °C. Uniform GaN growth was obtained with the pre sputtering of a thin Al film before the deposition of sp-AlN. Atomic force microscopy (AFM) measurements revealed that the density of pits originating from the ends of mixed/screw-type dislocations is about 109 cm-2, which is much lower than that of GaN grown on a metalorganic vapor phase epitaxy (MOVPE) deposited AlN intermediate layer. The decrease in the pit density might have originated from the small number of initial nuclei of GaN.

    DOI: 10.7567/JJAP.52.08JB16

  276. Fabrication of InGaN/GaN Multiple Quantum Wells on (1-101) GaN 査読有り

    Tomoyuki Tanikawa, Tomotaka Sano, Maki Kushimoto, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JC05   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    InGaN/GaN multiple quantum wells (MQWs) on semipolar (1101) GaN microstripes on a Si substrate were fabricated and their optical properties were investigated. From cathodoluminescence (CL) analysis, strong CL emission was obtained in an MQW emitting at 433 nm. However, dark lines appeared in MQWs emitting at longer wavelengths. These dark lines are attributed to lattice relaxation and the generation of misfit dislocations and stacking faults in an MQW, resulting in nonradiative centers. The internal quantum efficiency (IQE) was estimated from excitation-power-dependent photoluminescence analysis. The (1101) InGaN/GaN MQW had a high IQE owing to the high crystalline quality of the underlying GaN and the reduced piezoelectric field. The IQE at a carrier concentration of 1×1018 cm-3 in a sample emitting at 490 nm was as high as 90%. The efficiency decreased in a sample with a higher indium content in the MQW due to the generation of misfit dislocations and stacking faults.

    DOI: 10.7567/JJAP.52.08JC05

  277. Stacking Faults and Luminescence Property of InGaN Nanowires 査読有り

    Takuya Tabata, Jihyun Paek, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JE06   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    InGaN nanowires (NWs) were grown on (111)Si substrate using radio-frequency plasma-assisted molecular beam epitaxy, and the density of the stacking faults (SFs) in the InGaN NWs was estimated. High-density SFs were observed in the scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) images of the InGaN NWs, and a few zincblende layers appeared in the wurtzite structure. When growth temperature increased, the density of the SFs in the InGaN NW, the photoluminescence (PL) peak wavelength, and the full width at half maximum (FWHM) of PL spectra decreased, whereas the integrated PL intensity increased. These results suggest that a high growth temperature is effective for decreasing the density of SFs in InGaN NWs, and InGaN NWs grown at high temperature have strong PL luminescence due to the low In composition and the corresponding low SFs density.

    DOI: 10.7567/JJAP.52.08JE06

  278. Effects of Nano- and Microscale SiO2 Masks on the Growth of a-Plane GaN Layers on r-Plane Sapphire 査読有り

    Ji-Su Son, Cao Miao, Yoshio Honda, Masahito Yamaguchi, Hiroshi Amano, Yong Gon Seo, Sung-Min Hwang, and Kwang Hyeon Baik

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JC04   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the combined effects of a-plane GaN layers on a nanoscale patterned insulator on an r-plane sapphire substrate and epitaxial lateral overgrowth (ELOG) techniques. The fully coalescent a-plane GaN layer using nano- and microscale SiO2 masks showed the formation of nano- and microscale voids on the masks, respectively. Atomic force microscopy (AFM) measurements revealed a surface roughness of 0.63 nm and a submicron pit density of 7.8 ×107 cm-2. Photoluminescence (PL) intensity was enhanced by a factor of 9.0 in comparison with that of a planar sample. Omega full-width at half-maximum (FWHM) values of the (1120) X-ray rocking curve along the c- and m-axes were 553 and 788 arcsec, respectively. A plan-view cathodoluminescence (CL) mapping image showed high luminescence intensity on the SiO2 masks.

    DOI: 10.7567/JJAP.52.08JC04

  279. High Internal Quantum Efficiency Blue-Green Light-Emitting Diode with Small Efficiency Droop Fabricated on Low Dislocation Density GaN Substrate 査読有り

    Tomotaka Sano, Tomohiro Doi, Shunko Albano Inada, Tomohiko Sugiyama, Yoshio Honda, Hiroshi Amano, and Takashi Yoshino

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JK09   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We fabricated blue, blue-green, and green light-emitting diodes (LEDs) of different dislocation densities (DD) and characterized their internal quantum efficiency (IQE). The IQE of the blue LEDs fabricated using GaN substrate exceeded 90 percent, however, when we used a GaN-on-sapphire substrate, IQE was limited to 60 percent. Droop was reduced by use of the GaN substrate. The junction temperature of the GaN-on-sapphire substrate was found to be 200 degreeC although the junction temperature of the GaN substrate was 50 degreeC when a forward current of 100 A/cm2 was driven. A lowering of IQE in green LEDs to 60 percent was observed, even though we used a low-dislocation-density substrate.The junction temperature of blue-green and green LEDs was about 100 degreeC when a forward current of 177 A/cm2 was driven, which indicated that junction temperature is not a major factor for IQE suppression in green LEDs.

    DOI: 10.7567/JJAP.52.08JK09

  280. Growth Mode and Threading Dislocation Behavior of GaN Films Grown on Patterned Sapphire Substrate with Radial Stripe Pattern 査読有り

    Koji Okuno, Takahide Oshio, Naoki Shibata, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JB09   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A sapphire substrate with a grooved stripe pattern along different radial directions was prepared to investigate the effects of stripe direction on the growth mode and threading dislocation (TD) behavior of GaN films. When the stripe direction is oriented parallel to [1010]sapphire, the GaN films have a triangular structure that is formed by the GaN{1011} facets. As the stripe direction rotates from [1010]sapphire, nanosteps with a step height of around 80 nm are formed on the GaN{1011} facets and then the coalescence of GaN on the ridges and grooves advances. GaN films with a smooth surface and a TD density as low as 2.0×108 cm-2 were achieved when the stripe direction was rotated 3° from [1010]sapphire. Our result indicates that the surface roughness and TD density of GaN films can be controlled by precisely adjusting the angle of the stripe direction from [1010]sapphire.

    DOI: 10.7567/JJAP.52.08JB09

  281. Thick InGaN Growth by Metal Organic Vapor Phase Epitaxy with Sputtered InGaN Buffer Layer 査読有り

    Toshiya Ohata, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JB11   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A thick InGaN film was grown on a sapphire substrate by metal organic vapor phase epitaxy using a thin buffer layer of sputter-deposited InGaN. A thick film of highly luminescent In0.2Ga0.8N can be successfully grown at a rate as high as 2 µm/h. The crystal quality of InGaN grown on the sputter-deposited InGaN buffer layer was better than that of InGaN grown directly on the sapphire substrate. The sample showed n-type conduction with a carrier concentration and mobility of 5×1018 cm-3 and 3 cm2/(V·s), respectively.

    DOI: 10.7567/JJAP.52.08JB11

  282. Combination of ITO and SiO2/AlN Dielectric Multilayer Reflective Electrodes for UV-Emitting Diodes 査読有り

    Tsubasa Nakashima, Kenichiro Takeda, Hiroshi Shinzato, Motoaki Iwaya, Satoshi Kamiyama, Tetsuya Takeuchi, Isamu Akasaki, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JG07   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have investigated novel reflective electrodes by combining an ITO layer and a SiO2/AlN dielectric multilayer (DM) for UV-light-emitting diodes (LEDs). The reflectance of 10 pairs of SiO2/AlN DM reached 98.5 percent at 350 nm. As a result, the ITO/DM electrodes simultaneously satisfied the requirements of high reflectivity in the UV region, good contact characteristics, and current spreading. The light output power of the UV LED with an ITO/DM electrode is 1.2 and 1.6 times higher than those of LEDs with ITO/Al and Ni/Au electrodes, respectively.

    DOI: 10.7567/JJAP.52.08JG07

  283. GaN Nanowires Grown on a Graphite Substrate by Radio Frequency Molecular Beam Epitaxy 査読有り

    Shinta Nakagawa, Takuya Tabata, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JE07   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Self-assembled GaN and InGaN nanowires (NWs) were directly grown on a highly oriented pyrolytic graphite (HOPG) substrate by radio frequency molecular beam epitaxy (RF-MBE). The GaN NWs grown on HOPG had a shorter length and larger diameter than those grown conventionally on a Si(111) substrate based on the analysis of scanning electron microscopy (SEM) images. They were also found to have good crystalline qualities with few stacking faults, as determined by scanning transmission electron microscopy (STEM) analysis. Photoluminescence (PL) measurements at room temperature indicated that the luminescence intensity of the GaN NWs on HOPG is stronger than that of NWs grown on a Si(111) substrate; however, the InGaN NWs on both substrates showed similar tendencies with respect to the shift of the luminescence wavelength as a function of the growth temperature. While In incorporation decreased as the growth temperature increased, the uniformity of the InGaN NW arrays improved rapidly.

    DOI: 10.7567/JJAP.52.08JE07

  284. Concentrating Properties of Nitride-Based Solar Cells Using Different Electrodes 査読有り

    Mikiko Mori, Shinichiro Kondo, Shota Yamamoto, Tatsuro Nakao1, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JH02   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated the concentration properties of GaInN-based solar cells using different window electrodes. A significant difference was observed between the concentrating properties of the window electrode structures. It was clearly found that indium tin oxide (ITO) is suitable as an electrode. The short-circuit current density, open-circuit voltage, fill factor, and energy conversion efficiency of nitride-based solar cells fabricated using an ITO electrode were 7.1×102 mA/cm2, 2.2 V, 79%, and 4.0%, respectively, under an air mass filter of 1.5G at 300 suns and at room temperature.

    DOI: 10.7567/JJAP.52.08JH02

  285. Emission Wavelength Dependence of Internal Quantum Efficiency in InGaN Nanowires 査読有り

    Hideaki Murotani, Hiroya Andoh, Takehiko Tsukamoto, Toko Sugiura, Yoichi Yamada, Takuya Tabata, Yoshio Honda, Masatoshi Yamaguchi, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JE10   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The internal quantum efficiency (IQE) of InGaN nanowires with different emission wavelength of 485, 515, 555, and 580 nm has been studied by means of photoluminescence (PL) spectroscopy. It was found from the analysis of IQE as a function of excitation power density that the IQE was unchanged at about 100% under weak excitation conditions at low temperature. This indicated that the effects of nonradiative recombination processes were negligibly small at low temperature. Moreover, the IQE increased from 5 to 12% with increasing emission wavelength from 485 to 580 nm. Since the clear correlation between the IQE and the PL blue shift due to band filling effects of localized states was observed, the increase in the IQE reflected the increase in the effect of exciton localization with increasing indium composition.

    DOI: 10.7567/JJAP.52.08JE10

  286. Luminescence of Acceptors in Mg-Doped GaN 査読有り

    Bo Monemar, Sergey Khromov, Galia Pozina, Plamen Paskov, Peder Bergman, Carl Hemmingsson, Lars Hultman, Hiroshi Amano, Vitaliy Avrutin, Xing Li, and Hadis Morkoç

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JJ03   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    It is concluded that the typical PL peaks at 3.466 eV (ABE1)and the broader 3.27 eV DAP PL are the expected standard PL signatures of the substitutional Mg acceptor. Additional broader peaks at 3.455 eV (ABE2) and 3.1 eV are suggested to be related to the same acceptors perturbed by nearby basal plane stacking faults. The low temperature metastability of PL spectra is assigned to a nonradiative metastable deep level.

    DOI: 10.7567/JJAP.52.08JJ03

  287. Analysis of Broken Symmetry in Convergent-Beam Electron Diffraction along <11-20 > and <1-100 > Zone-Axes of AlN for Polarity Determination 査読有り

    Masataka Imura, Ujjal Gautam, Kiyomi Nakajima, Yasuo Koide, Hiroshi Amano, and Kenji Tsuda

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JE15   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To accurately and easily determine the polarity of AlN using transmission electron microscopy, we compare the convergent-beam electron diffraction (CBED) patterns along the widely used <1120 > and <1100 > zone-axes. For the <1120 > zone-axis, the diffraction disk of g= 0002 differs from that of g= 0002, while for <1100 >, the diffraction disks of g= 0002 and 0002 are similar. The preferential clarity of these two disks is explained using Bloch-wave dynamical theory. To further support the explanation, we compare the results of GaN case. On the basis of our analysis, we conclude that the CBED patterns of the <1120 > zone-axis are more useful for accurately determining AlN polarity compared to the CBED patterns along the <1100 > zone-axis.

    DOI: 10.7567/JJAP.52.08JE15

  288. Microstructure Analysis of AlGaN on AlN Underlying Layers with Different Threading Dislocation Densities 査読有り

    Kimiyasu Ide, Yuko Matsubara, Motoaki Iwaya, Satoshi Kamiyama, Tetsuya Takeuchi, Isamu Akasaki, and Hiroshi Amano

    Jpn. J. Appl. Phys.   52 巻 ( 8 ) 頁: 08JE22   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Using the epitaxial lateral growth technique, we compared the crystallinity and relaxation ratio of 3-µm- and 200-nm-thick Al0.5Ga0.5N on an AlN template and AlN grown by epitaxial lateral overgrowth (ELO-AlN), both of which were grown on a sapphire substrate. Although the relaxation ratios of 3-µm-thick Al0.5Ga0.5N were almost the same, the misfit dislocation density at the interface and the density of threading dislocations reaching the surface of Al0.5Ga0.5N were significantly different. Also, the increase in the density of newly generated misfit dislocations was found to be highly dependent on the quality of the AlN underlying layer. We also discuss the difference in the initial growth mode of each Al0.5Ga0.5N sample.

    DOI: 10.7567/JJAP.52.08JE22

  289. Progress and Prospect of the Growth of Wide-Band-Gap Group III Nitrides: Development of the Growth Method for Single-Crystal Bulk GaN 査読有り

    Hiroshi Amano

    Japanese journal of applied physics   52 巻 ( 5 ) 頁: 050001-1-050001-10   2013年5月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    With the continuously increasing demand for the conservation and generation of energy, bulk substrates of group III nitride semiconductors are highly expected to maximize their potential. In this report, I review the current status of the growth methods for bulk GaN single crystals used for substrates as well as summarize the characteristics of blue light-emitting diodes (LEDs), heterojunction field-effect transistors (HFETs), and photovoltaic cells on GaN substrates.

    DOI: 10.7567/JJAP.52.050001

  290. AlN/air distributed Bragg reflector by GaN sublimation from microcracks of AlN 査読有り

    T. Mitsunari, T. Tanikawa, Y. Honda, M. Yamaguchi, H. Amano

    Journal of Crystal Growth   370 巻 ( 1 ) 頁: 16-21   2013年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The GaN/AlN multilayer structure was grown on a stripe-patterned and dot-patterned Si substrate, and subsequently annealed at 1200 °C in H2 and NH3 atmosphere. We achieved an AlN/air structure by the decomposition of GaN from the microcracks of AlN. Partially crack-free AlN layers were observed over a 5×5 μm area in the c-plane of AlN/air DBRs.

    DOI: 10.1016/j.jcrysgro.2012.09.062

  291. Structural evolution of AlN buffer and crystal quality of GaN films on a- and c-sapphire grown by metalorganic vapor phase epitaxy 査読有り

    Okuno, Koji; Oshio, Takahide; Shibata, Naoki; Honda, Yoshio; Yamaguchi, Masahito; Tanaka, Shigeyasu; Amano, Hiroshi

    Physica Status Solidi C   10 巻 ( 3 ) 頁: 369-372   2013年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 0.1002/pssc.201200587

  292. Effects of low energy e-beam irradiation on cathodoluminescence from GaN 査読有り

    Suihkonen, S.; Nykaenen, H.; Tanikawa, T.; Yamaguchi, M.; Honda, Y.; Amano, H.

    Physica Status Solidi A   210 巻 ( 2 ) 頁: 383-385   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssa.201228457

  293. Development of High-Density Nitrogen Radical Source for Low Mosaicity and High Rate Growth of InGaN Films in Molecular Beam Epitaxy 査読有り

    Chen, S ; Kawai, Y ; Kondo, H ; Ishikawa, K ; Takeda, K ; Kano, H ; Sekine, M ; Amano, H Hori, M

    Japanese Journal of Applied Physics   52 巻 ( 2 ) 頁: 021001-021006   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A high-density radical source (HDRS) was developed by optimizing the antenna structure and introducing an external magnetic field to plasma. Nitrogen radical generation by the HDRS at a density of 2.3 ×1012 atoms cm-3, which was one order higher than that for the conventional radical source (CRS), was achieved. The HDRS- and CRS-assisted InGaN growth in molecular beam epitaxy (MBE) was carried out. For the HDRS case, a diffraction peak in the X-ray rocking curve of the grown InGaN films showed a narrower peak, which width below 600 arcsec even with a high growth rate of 1.4 µm/h for InGaN. MBE with the assistance of HDRS has a great potential in the growth of nitride films with a lower mosaicity and a higher growth rate.

    DOI: 10.7567/JJAP.52.021001

  294. Surface potential effect on excitons in AlGaN/GaN quantum well structures 査読有り

    Pozina, G.; Hemmingsson, C.; Amano, H.; Monemar, B.

    Applied Physics Letters   102 巻 ( 8 ) 頁: 082110/1-082110/4   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.4793568

  295. Individual roles of atoms and ions during hydrogen plasma passivation of surface defects on GaN created by plasma etching 査読有り

    Chen, Shang; Ishikawa, Kenji; Lu, Yi; Kometani, Ryosuke; Kondo, Hiroki; Tokuda, Yutaka; Egawa, Takashi; Amano, Hiiroshi; Sekine, Amano; Hori, Masaru

    Japanese Journal of Applied Physics   51 巻 ( 11 ) 頁: 111002/1-11102/5   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In the recovery of photoluminescence intensities for band-edge emissions at around 3.47 eV in the case of gallium nitride (GaN), we have studied the individual roles of hydrogen atoms (H) and hydrogen ions (H-n(+)). Surface defects such as nitrogen vacancies created by plasma etching were passivated by H termination. By utilizing hydrogen plasmas, we clarified the recovery efficiency by optical and stoichiometrical improvements with respect to the balance between the fluxes of H and H-n(+). By deflecting H-n(+) by applying an electric field, the efficiency was improved using an identical H dosage, since the simultaneous irradiation of the energetic H-n(+) promoted the desorption of the formed passivated Ga-H bonds.

    DOI: 10.1143/JJAP.51.111002

  296. Correlation between device performance and defects in GaInN-based solar cells 査読有り

    Mori, Mikiko; Kondo, Shinichiro; Yamamoto, Shota; Nakao, Tatsuro; Fujii, Takahiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Applied Physics Express   5 巻 ( 8 ) 頁: 082301/1-082301/3   2012年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated the correlation between the device performance and defects, such as V-shaped pits and threading dislocations, in GaInN-based solar cells. To realize high-performance GaInN-based solar cells with a high open-circuit voltage and fill factor, it is essential to realize a low pit density of less than 10(7) cm(-2). In this study, we were unable to observe clear evidence of any effect of the threading dislocation density in the GaN underlying layer.

    DOI: 10.1143/APEX.5.082301

  297. MOVPE growth of nonpolar a-plane GaN with low oxygen contamination and specular surface on a freestanding GaN substrate 査読有り

    Yasuhiro Isobe, Hiromichi Ikki, Tatsuyuki Sakakibara, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki,Takayuki Sugiyama, Hiroshi Amano, Mamoru Imade, Yusuke Mori

    Journal of Crystal Growth   351 巻 ( 1 ) 頁: 126-130   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated unintentionally doped nonpolar a- and m-plane GaN layers grown by metalorganic vapor phase epitaxy under several sets of conditions on freestanding a- and m-plane GaN substrates. Oxygen contamination in a-plane GaN is greatly reduced by increasing the V/III ratio during growth. As a result, a high-resistivity GaN buffer layer for an AlGaN/GaN heterostructure field-effect transistor was realized.

  298. In-situ void formation technique using an AlN shell structure grown on GaN stripes on Si(111) and c-plane sapphire substrates 査読有り

    Mitsunari, Tadashi; Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    Physca Status Solidi c   9 巻 ( 3-4 ) 頁: 480-483   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We proposed an in-situ void formation technique using high-temp. AlN growth on GaN stripes in order to reduce residual stress. Microcracks were obsd. during the growth of AlN; the GaN stripes then sublimated from the microcracks while keeping the AlN shell, resulting in void formation in the AlN shell structure. After GaN regrowth on this AlN shell structure, we successfully coalesced the GaN stripes to form a smooth, thick GaN layer having voids at the GaN/substrate interface. Raman spectroscopy confirmed that the residual tensile stress was decreased. The thermal stress decreased owing to the sepn. between the GaN layer and a foreign substrate.

    DOI: 10.1002/pssc.201100502

  299. Small current collapse in AlGaN/GaN HFETs on a-plane GaN self-standing substrate 査読有り

    T. Sugiyama, Y. Honda, M. Yamaguchi, H. Amano, Y. Isobe, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, M. Imade, Y. Kitaoka, Y. Mori

    Physica Status Solidi c   9 巻 ( 3-4 ) 頁: 875-878   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We measured drain bias stress effects and current collapse in AlGaN/ GaN heterostructure field-effect transistors (HFETs) on a-plane and c-plane GaN substrates. An a-plane AlGaN/GaN HFET (a-HFET) shows small current collapse with a threshold voltage (Vth = -1.8 V). On the other hand, a c-plane HFET (c-HFET) with the same barrier thickness (20 nm) shows a small current collapse, although Vth was neg. large (Vth = -4 V). Current collapse in a-HFET was not large compared with that in conventional c-HFET on GaN. A c-HFET on sapphire was also measured. The current collapses in HFETs on sapphire were larger than that in HFETs on a GaN substrate. The current collapses in the thin-barrier c-HFET (Vth = -1.8 V) were particularly large. Therefore, an a-plane device is promising for a small or pos. Vth with small current collapse.

    DOI: 10.1002/pssc.201100397

  300. Laser lift-off of AlN/sapphire for UV light-emitting diodes 査読有り

    Aoshima, Hiroki; Takeda, Kenichiro; Takehara, Kosuke; Ito, Shun; Mori, Mikiko; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Physica Status Solidi C   9 巻 ( 3-4 ) 頁: 753-756   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on laser lift-off (LLO) of AlN/sapphire for UV light-emitting diodes (LEDs). Underfill between chip and submount is a key factor for the successful LLO of AlN/sapphire. We fabricated thin-film-flip-chip UV LEDs with a peak wavelength of 343 nm using the LLO. Moreover surface texturing was carried out on the exfoliated AlN surface. The light output power from the UV LED after the LLO and the surface texture at exfoliated surface is 1.7 times higher than that before the LLO at 20 mA.

    DOI: 10.1002/pssc.201100491

  301. Growth of InGaN nanowires on a (111)Si substrate by RF-MBE 査読有り

    Tabata, Takuya; Paek, Jihyun; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    Physica Status Solidi c   9 巻 ( 3-4 ) 頁: 646-649   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have grown InGaN nanowires (NWs) on a (111)Si substrate directly by radio-frequency plasma-assisted mol. beam epitaxy (RF-MBE), and investigated their In compositional distribution by energy dispersive x-ray spectroscopy (EDX). The In compn. line profiles of InGaN NWs measured by EDX are different at each position in the InGaN NWs, and In is most easily incorporated into the top of NWs. The In compn. at the top of the NWs depends on the growth temp. and the In flux ratio. However, the In compns. at other positions is not dependent on these factors. Thus, these results might be due to the limited diffusion of In atoms from the top of the NWs towards the NWs/Si interface.

    DOI: 10.1002/pssc.201100446

  302. Fabrication of AlInN/AlN/GaInN/GaN heterostructure field-effect transistors 査読有り

    Kazuya Ikeda, Yasuhiro Isobe, Hiromichi Ikki, Tatsuyuki Sakakibara, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, Hiroshi Amano

    Physica Status Solidi c   9 巻 ( 3-4 ) 頁: 942-944   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the electrical properties of AlInN/GaInN
    heterostructures fabricated with InN molar fractions of 0 to 0.6 in the GaInN layer. High-density two-dimensional electron gases are formed near the interfaces of AlInN/AlN/GaInN at InN molar fractions of 0.3 and 0.6.
    The Al0.82In0.18N/AlN/Ga0.4In0.6N/GaN heterostructure
    field-effect transistors exhibited static characteristics.
    The maximum drain-source current reached a value of
    0.26 A/mm.

    DOI: 10.1002/pssc.201100492

  303. High carrier concentration in high Al-composition AlGaN-channel HEMTs 査読有り

    Hashimoto, Shin; Akita, Katsushi; Yamamoto, Yoshiyuki; Ueno, Masaki; Nakamura, Takao; Yafune, Norimasa; Sakuno, Keiichi; Tokuda, Hirokuni; Kuzuhara, Masaaki; Takeda, Kenichiro; Iwaya, Motoaki; Amano, Hiroshi

      9 巻 ( 2 ) 頁: 373-376   2012年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    High Al-compn. (Al = 51%) and low Al-compn. (Al = 20%) AlGaN-channel high-electron-mobility transistors (HEMTs) on AlN layers with very high carrier concn. were demonstrated. In two types of HEMTs, 2-dimensional electron gases (2DEG) were clearly obsd. and peak carrier concn. and sheet carrier concn. were approx. 1020 cm-3 and higher than 2 × 1013 cm-2, resp. From the X-ray diffraction (XRD) measurements, it was obsd. that the AlGaN channel layers on the AlN layers were partially relaxed and the degree of relaxation decreased with increasing Al-compn. of AlGaN channel layers. Therefore the misfit dislocations in the high Al-compn. HEMTs were considered to be lower than those in the low Al-compn. HEMTs. Furthermore, it was revealed that very high Al-compn. of AlGaN barrier layers can be grown coherently on the AlGaN channel layers in consequence of the partly relaxation of the AlGaN channel layers, which of lattice consts. of a-axis were smaller than that of fully relaxed AlGaN channel layers. Therefore very high carrier concn. of 2DEG can be obtained in spite of the high Al-compn. of AlGaN channel layers. We considered that this high carrier concn. of 2DEG was necessary to demonstrate high Al-compn. AlGaN-channel HEMTs.

    DOI: 10.1002/pssc.201100289

  304. 窒化物ワイドギャップ半導体の現状と展望  ―バルクGaN単結晶成長技術開発の観点から― 査読有り

    天野 浩

    応用物理   81 巻 ( 6 ) 頁: 455-463   2012年6月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    GaNのバルク成長の歴史と展望を概説した。

  305. Crack-Free AlN/GaN Distributed Bragg Reflectors on AlN Templates 査読有り

    Kouta Yagi, Mitsuru Kaga, Kouji Yamashita, Kenichirou Takeda, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Hiroshi Amano, and Isamu Akasaki

    Japanese Journal of Applied Physics   51 巻   頁: 051001   2012年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have demonstrated crack-free 30-pair-AlN/GaN distributed Bragg reflectors (DBRs) grown on AlN templates for the first time. A reasonably high reflectivity of 97.5% was obtained. X-ray diffraction measurements revealed that the AlN templates cause compressive stress in DBRs. At the same time, the AlN/GaN DBRs were found to relax to average AlGaN alloys with AlN mole fractions determined by the thickness ratio of the AlN layer to one pair of AlN and GaN in DBRs regardless of the underlying template, AlN or GaN.

    DOI: 10.1143/JJAP.51.051001

  306. Growth of GaN and AlGaN on (100) beta-Ga2O3 substrates 査読有り

    Shun Ito, Kenichiro Takeda, Kengo Nagata, Hiroki Aoshima, Kosuke Takehara, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, Hiroshi Amano

      9 巻 ( 3-4 ) 頁: 519-522   2012年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The crystalline quality of GaN and Al0.08Ga0.92N epitaxial layers on (100) β-Ga2O3 substrates was significantly improved by the facet-controlled growth method. The facets were controlled by changing the nitrogen ambient thermal annealing temperature. We demonstrated the highcrystalline-quality GaN and Al0.08Ga0.92N on β-Ga2O3 substrates, which were comparable to GaN and AlGaN on sapphire substrates using low-temperature buffer layers.
    This method is useful for the fabrication of verticaltype ultraviolet (UV) light-emitting diodes (LEDs) on β-Ga2O3 substrates.

    DOI: 10.1002/pssc.201100499

  307. Properties of nitride-based photovoltaic cells under concentrated light illumination 査読有り

    Shota Yamamoto, Mikiko Mori, Yosuke Kuwahara, Takahiro Fujii, Tatsuo Nakao, Shinichiro Kondo, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, Hiroshi Amano

    Physica Status Solidi Rapid Research Letter   6 巻 ( 4 ) 頁: 145-147   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated the properties of nitride-based solar cells under concentrated light illumination from 1 to 200 suns. The conversion efficiency of our solar cells increased with increasing concentration up to 200 suns. The short-circuit cur- rent density, open-circuit voltage, fill factor, and conversion efficiency were 510 mA/cm2, 1.9 V, 70%, and 3.4%, respectively, under an air mass filter of 1.5G at 200 suns and room temperature. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

    DOI: DOI: 10.1002/pssr.201206038

  308. Development of AlN/diamond heterojunction field effect transistors 査読有り

    Masataka Imura, Ryoma Hayakawa, Hirotaka Ohsato, Eiichiro Watanabe, Daiju Tsuya, Takahiro Nagata, Meiyong Liao, Yasuo Koide, Jun-ichi Yamamoto, Kazuhito Ban, Motoaki Iwaya, Hiroshi Amano

    Diamond and Related Materials   24 巻   頁: 206-209   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    AlN/diamond heterojunction field effect transistors with p-channel and normally-on depletion mode are developed, and the device performance is improved by reducing the contact resistances at source and drain contacts reported previously. The heterojunction structure is constructed from a c-axis-oriented AlN epilayer grown on oxygen-terminated (111) diamond substrate by metal-organic vapor phase epitaxy at temperatures as high as 1250 °C. Thermal treatment in the mixed hydrogen (H2) and ammonia atmosphere just before AlN growth improves the AlN adhesion to diamond surface. In addition, this treatment simultaneously produces a much larger surface hole-carrier density than that obtained by conventional H2-plasma treatment. X-ray photoelectron spectroscopy reveals the existence of carbon-nitrogen bonds at the diamond surface, and these may be responsible for such a large hole density. These results are promising in relation to new opportunities for developing diamond-based power electronic devices.

  309. Indium-Tin Oxide/Al eflective Electrodes for Ultraviolet Light-Emitting Diodes 査読有り

    Kosuke Takehara, Kenichiro Takeda, Shun Ito, Hiroki Aoshima, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, and Hiroshi Amano

    Japanese Journal of Applied Physics   51 巻   頁: 042101   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JJAP.51.042101

  310. Indium-Tin oxide/Al reflective electrodes for ultraviolet light-emitting diodes 査読有り

    Takehara, Kosuke; Takeda, Kenichiro; Ito, Shun; Aoshima, Hiroki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

      51 巻 ( 4 ) 頁: 042101/1-042101/4   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated indium-tin oxide (ITO)/Al reflective electrodes for improving the light extraction efficiency of UV light-emitting diodes (LEDs). The ITO layer showed high transparency in the UV region upon optimization of the thickness and annealing temperature. As a result, the ITO/Al electrode exhibited both high reflectivity in the UV region and good contact characteristics simultaneously. Using this electrode, we succeeded in improving the light output power of a 350 nm UV-A LED.

    DOI: 10.1143/JJAP.51.042101

  311. Strain relaxation in thick (1-101) InGaN grown on GaN/Si substrate 査読有り

    Tomoyuki Tanikawa, Yoshio Honda, Masahito Yamaguchi, Hiroshi Amano, Nobuhiko Sawaki

    Physica Status Solidi b   249 巻   頁: 468-471   2012年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1002/pssb.201100445

  312. Enhancement of two-dimensional electron gases in AlGaN-channel high-electron-mobility transistors with AlN barrier layers 査読有り

    Hashimoto Shin; Akita Katsushi; Yamamoto Yoshiyuki, HIroshi Amano

    Physica Status Solidi a   209 巻   頁: 501-504   2012年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1002/pssa.201100379

  313. Improvement of Light Extraction Efficiency for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes 査読有り

    Tetsuhiko Inazu, Shinya Fukahori, Cyril Pernot, Myung Hee Kim, Takehiko Fujita, Yosuke Nagasawa, Akira Hirano, Masamichi Ippommatsu, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Masahito Yamaguchi, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki

    Japanese Journal of Applied Physics   50 巻   頁: 122101   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with aluminum reflective electrodes deposited to cover both p- and n-mesh contact electrodes have been fabricated. A 1.55-fold increase in light extraction efficiency has been demonstrated. Despite their reduced contact area, the LEDs exhibited only a slight increase in forward voltage of 0.45 V at 20 mA. Also, their 50% lifetime was estimated to be about 10,000 h at 20 mA DC at room temperature by extrapolation. Owing to the reflective electrodes, a 288 nm LED with external quantum efficiency as high as 5.4% was achieved. The light output power was 4.6 mW at 20 mA.

    DOI: 10.1143/JJAP.50.122101

  314. Dependence of Resonance Energy Transfer on Exciton Dimensionality 査読有り

    Jan Junis Rindermann, Galia Pozina, Bo Monemar, Lars Hultman, Hiroshi Amano, and Pavlos G. Lagoudakis

    Physical Review Letters   107 巻   頁: 236805   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigate the dependence of resonance energy transfer from Wannier-Mott excitons to an organic overlayer on exciton dimensionality. We exploit the excitonic potential disorder in a single quantum well to tune the balance between localized and free excitons by scaling the Boltzmann distribution of excitons through temperature. Theoretical calculations predict the experimentally observed temperature dependence of resonance energy transfer and allow us to quantify the contribution of localized and free excitons. We show that free excitons can undergo resonance energy transfer with an order of magnitude higher rate compared to localized excitons, emphasizing the potential of hybrid optoelectronic devices utilizing resonance energy transfer as a means to overcome charge transfer related limitations.

  315. Fabrication of Nonpolar a-Plane Nitride-Based Solar Cell on r-Plane Sapphire Substrate 査読有り

    Applied Physics Express   4 巻   頁: 101001   2011年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    サファイアr面基板上に成長した窒化物太陽光発電素子に関する初めての論文。

    DOI: 10.1143/APEX.4.101001

  316. AlGaN-Based Deep Ultraviolet Light-Emitting Diodes Fabricated on Patterned Sapphire Substrates 査読有り

    Myunghee Kim, Takehiko Fujita, Shinya Fukahori, Tetsuhiko Inazu, Cyril Pernot, Yosuke Nagasawa, Akira Hirano, Masamichi Ippommatsu, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Masahito Yamaguchi, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki

    Applie Physics Express   4 巻   頁: 092102   2011年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/APEX.4.092102

  317. AlGaN/GaN Heterostructure Field-Effect Transistors on Fe-Doped GaN Substrates with High Breakdown Voltage 査読有り

    Yoshinori Oshimura, Takayuki Sugiyama, Kenichiro Takeda, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano

    Japanese Journal of Applied Physics   50 巻   頁: 084102   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    lGaN/GaN heterostructure field-effect transistors (HFETs) were fabricated by metalorganic vapor phase epitaxy (MOPVE) on c-plane Fe-doped GaN (GaN:Fe) substrates with different growth conditions of GaN buffer layers. The GaN buffer layers were grown at a V/III ratio of 272 at 300 Torr to realize highly resistive GaN buffer layers with automatic carbon doping. HFETs with carbon-doped GaN buffer layers showed the best characteristics among all the samples in this study. The carbon concentration was 5×1016 cm-3. In the sample with a gate-drain length of 50 µm, the off-state breakdown voltage was 2 kV or higher and the on-resistance was 18.5 mΩ·cm2. We found that the carbon-doped GaN buffer layers are necessary for high breakdown voltages even using semi-insulating GaN:Fe substrates.

  318. Luminescence related to high density of Mg-induced stacking faults in homoepitaxially grown GaN 査読有り

    S. Khromov, C. G. Hemmingsson, H. Amano, B. Monemar, L. Hultman, and G. Pozina

    Pysical Review   B84 巻   頁: 075324   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevB.84.075324

  319. Reduction in threshold current density of 355 nm UV laser diodes 査読有り

    Nagata, Kengo; Takeda, Kenichiro; Nonaka, Kentaro; Ichikawa, Tomoki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Yoshida, Harumasa; et al

    Physica Status Solidi C   8 巻 ( 5 ) 頁: 1564-1568   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have investigated the characteristics of 355 nm UV laser diodes. Two laser diode structures were prepd. on a grooved AlGaN template as well as on a flat AlGaN template. The threading dislocation densities on the grooved and flat AlGaN were 2.5 × 108 cm-2 and 6.5 × 109 cm-2, resp. The threshold c.d. of the laser diode on the grooved AlGaN was 6 kA/cm2, while no lasing was obsd. from the laser diode on the flat AlGaN. We also estd. the internal quantum efficiency as well as the injection efficiency in the UV laser diode structures by considering internal quantum efficiency of both optical and elec. excitation. At a carrier d. of 1.2 × 1019 cm-3, the internal quantum efficiency of the laser diode structure on the grooved AlGaN was about 50%. This is twice that of the laser diode on the flat AlGaN. At the same time, the internal quantum efficiency estd. from the optical excitation also reached about 50%, even at a carrier d. of 3 × 1018 cm-3. This implies that the injection efficiency in our UV laser diode structure was only 25%. Improving the injection efficiency should be effective for significantly reducing the threshold c.d.

  320. Transparent electrode for UV light-emitting-diodes 査読有り

    Takehara, Kosuke; Takeda, Kenichiro; Nagata, Kengo; Sakurai, Hisashi; Ito, Shun; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2375-2377   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have investigated the transparent electrodes using indium tin oxide (ITO) for UV light-emitting diodes (LEDs). The carrier concn. of ITO was increased from 1.1 × 1018 to 1.5 × 1021 cm-3 after annealing under N2 ambient at 600 °C. The fundamental absorption edge was also shifted to a shorter wavelength owing to the increase in carrier concn., through the so-called the Burstein-Moss effect. The annealed ITO forms an ohmic contact with p-GaN with a specific contact resistance of 1.2 × 10-3 Ωcm2. The light output power of a 350 nm LED with the annealed ITO contact is 1.2 times higher than that with a conventional Ni/Au contact.

  321. Selective MOVPE growth of InGaN/GaN MQW on microfacet GaN stripes 査読有り

    Tanikawa, Tomoyuki; Murase, Tasuku; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2038-2040   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We demonstrated the effects of growth conditions such as growth pressure and growth temp. during the selective growth of InGaN/GaN multiple quantum wells (MQWs) on semipolar GaN microstripes on Si substrates. Grown layers exhibited the ridge growth, which indicates the thickness fluctuation, owing to the source supply from the apexes of the GaN microstructure. Ridge growth was suppressed by increasing growth pressure and decreasing growth temp. Cathode luminescence (CL) anal. showed uniform luminescence. As a result, high pressure and low temp. are suitable for obtaining uniform heterostructures in the selective growth of InGaN/GaN MQWs on GaN microstripes.

  322. Achieving high-growth-rate in GaN homoepitaxy using high-density nitrogen radical source 査読有り

    Kawai, Yohjiro; Chen, Shang; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi; Kondo, Hiroki; Hirmatsu, Mineo; Kano, Hiroyuki; Yamakawa, Koji; Den, Shoji; et al

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2089-2091   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The key issue in GaN growth by radio-frequency plasma-assisted mol. beam epitaxy is the low growth rate compared with that obtained using an ammonia source. To reduce the processing time and to improve the cryst. quality of the epilayer, a high-d. radical source (HDRS) with high stability has been developed. The growth rate of the GaN epilayer was improved using the HDRS rather than a conventional radical source. During the growth, a sharp streak pattern obtained by RHEED was maintained. An atomically smooth surface was confirmed by at. force microscopy observation.

  323. AlGaN/GaInN/GaN heterostructure field-effect transistor 査読有り

    Ikki, Hiromichi; Isobe, Yasuhiro; Iida, Daisuke; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Bandoh, Akira; Udagawa, Takashi

    Physica Status Solidi A   208 巻 ( 7 ) 頁: 1614-1616   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the elec. properties of AlGaN/GaInN heterostructures fabricated with various InN molar fractions from 0 to 0.60 in GaInN on a GaN template. The sheet carrier d. of the AlGaN/GaInN heterostructure monotonically increased with increasing InN molar fraction in GaInN, reaching 5.0 × 1013 cm-2 at an InN molar fraction of 0.60. The Al0.30Ga0.70N/Ga0.40In0.60N heterostructure exhibited static field-effect transistor (FET) characteristics.

  324. Development of high efficiency 255-355 nm AlGaN-based light-emitting diodes 査読有り

    Pernot, Cyril; Fukahori, Shinya; Inazu, Tetsuhiko; Fujita, Takehiko; Kim, Myunghee; Nagasawa, Yosuke; Hirano, Akira; Ippommatsu, Masamichi; Iwaya, Motoaki; Kamiyama, Satoshi, Amano Hiroshi; et al

    Physica Status Solidi A:   208 巻 ( 7 ) 頁: 1594-1596   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the fabrication and characterization of high efficiency UV light emitting diodes (LEDs) with emission wavelength ranging from 255 to 355 nm. Epi-layers of UV LEDs were grown on AlGaN templates with sapphire substrates. Flip-chip configuration without removing sapphire is used for characterization of the UV LEDs. External quantum efficiencies (EQEs) over 3% were obtained for all the investigated wavelengths with max. value reaching 5.1% for 280 nm LED. Under RT DC operation at a current of 500 mA, output powers of 38, 77, and 64 mW were measured for 257, 280, and 354 nm, resp. By using enhanced light extn. technologies, such as, moth-eye structure on the back side of the sapphire substrate, we expect to improve these values by up to 50%.

  325. Drain bias stress and memory effects in AlGaN/GaN heterostructure field-effect transistors with p-GaN gate 査読有り

    Sugiyama, Takayuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi; Oshimura, Yoshinori; Iida, Daisuke; Iwaya, Motoaki; Akasaki, Isamu

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2424-2426   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We measured the drain bias stress effects in normally off mode AlGaN/GaN (JHFETs) with a p-GaN gate, whose AlGaN barrier was exposed to air by dry etching. A large current collapse and a memory effect decreased the drain current (IDS). IDS of an unpassivated sample became the off leakage level of normally off mode JHFETs at a drain stress bias of 15 V. On the other hand, IDS in SiN-passivated JHFETs decreased at a slow rate upon applying drain stress bias. The decrease in IDS in SiN-passivated JHFETs was almost the same as that in asgrown HFETs. These drain stress and memory effects were perfectly deletable by light exposure, and were rewritable similarly in an EPROM.

  326. GaInN-based solar cells using GaInN/GaInN superlattices 査読有り

    Fujii, Takahiro; Kuwahara, Yousuke; Iida, Daisuke; Fujiyama, Yasuhara; Morita, Yoshiki; Sugiyama, Toru; Isobe, Yasuhiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; et al

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2463-2465   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the fabrication of GaInN-based solar cells using GaInN/GaInN superlattices as active layers and also as underlying layers beneath the active layers. We obtained pit-free surfaces, even with a high InN molar fraction, using the superlattices. As a result, the max. external and internal quantum efficiencies reached 60%, and 88%, resp. The open-circuit voltage of the soalr cells was 1.77 V, the short-circuit c.d. was 3.08 mA/cm2, and the fill factor was 70.3%. A conversion efficiency of 2.46% was achieved at room temp. under simulared 1.5 sun × AM1.5G illumination using a solar simulator.

  327. Injection efficiency in AlGaN-based UV laser diodes 査読有り

    Nagata, Kengo; Takeda, Kenichiro; Oshimura, Yoshinori; Takehara, Kosuke; Aoshima, Hiroki; Ito, Shun; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; et al

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2384-2386   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We evaluated AlGaN-based 355 nm UV laser diodes prepd. under two different Mg activation conditions. The annealing processes for Mg activation in p-layers were carried out under N2 or O2 ambient to investigate the effect of the ambient gas on the laser characteristics. The threshold current densities and operating voltages of the UV laser diodes were improved by annealing under O2 compared with those under N2. We then estd. the injection efficiencies of the laser diode structures by considering the internal quantum efficiencies of optical excitation and elec. excitation. The internal quantum efficiency of the elec. excited spontaneous emission from the laser structure annealed under O2 reached 50% at a carrier d. of 7.0 × 1018 cm-3, while the structure annealed under N2 required a 1.8-fold higher carrier d. of 1.2 × 1019 cm-3 to reach the same internal quantum efficiency. In addn., the internal quantum efficiency estd. from optical excitation reached 50% even at a carrier d. of 3.0 × 1018 cm-3. This implies that the injection efficiencies in the UV laser diode structures annealed under N2 and O2 were 25% and 45%, resp. Mg activation by O2 annealing is effective for increasing the injection efficiency.

  328. Low leakage current in AlGaN/GaN HFETs with preflow of Mg source before growth of u-GaN buffer layer 査読有り

    Oshimura, Yoshinori; Sugiyama, Takayuki; Takeda, Kenichiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Physica Status Solidi A   208 巻 ( 7 ) 頁: 1607-1610   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    AlGaN/GaN heterostructure field-effect transistors were grown by metalorg. vapor phase epitaxy on Fe-doped GaN substrates with a preflow of the Mg source. We realized a low drain leakage current, 1.05 μA/mm, at VDS = 20 V and VGS = -5 V with LGD = 3 μm. This leakage current was one order of magnitude lower than that obtained without a preflow of the Mg source. The breakdown voltage was over 250 V with LGD = 10 μm. The on resistance was estd. to be 3.6 mΩ cm2. No significant redistribution or memory effect of Mg was obsd. by secondary ion mass spectroscopy measurement.

  329. Optical properties of (1-101) InGaN/GaN MQW stripe laser structure on Si substrate 査読有り

    Murase, Tasuku; Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2160-2162   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A smooth laser structure on (1-101) GaN microstripes was successfully fabricated on a patterned (100) 8°-off Si substrate. The sample has a high internal quantum efficiency (IQE) compared with blue LEDs on a sapphire substrate. The high-d. excitation PL spectrum obsd. from the cross section of the sample shows marked narrowing, and the integral PL intensity also shows a steep increase. These results indicate the onset of stimulated emission from an InGaN-based multi quantum well (MQW) active layer on (1-101) GaN (100) Si. To the best of our knowledge, this is the first report of the observation of a stimulated emission from a (1-101) MQW on a Si substrate. We succeeded in fabricating and verifying the high-quality laser structure on semipolar (1-101) GaN on a Si substrate.

  330. Optimization of initial MOVPE growth of non-polar m- and a-plane GAN on Na flux grown LPE-GaN substrates 査読有り

    Isobe, Yasuhiro; Iida, Daisuke; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Imade, Mamoru; Kitaoka, Yasuo; et al

    Physica Status Solidi C   8 巻 ( 7-8 ) 頁: 2095-2097   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We optimized the initial GaN growths of nonpolar m- and a-plane GaN grown on liq. phase epitaxy (LPE-) GaN substrates. Such nonpolar LPE-GaN substrates were produced by cutting slices from c-plane LPE-GaN bulk single crystals grown by the Na-flux method. We investigated the qualities of epitaxially grown GaN layers on the LPE-GaN substrates, with different polishing methods, which are chem. mech. polishing and plasma dry etch polishing. We found that the cryst. quality of epitaxial GaN on m-plane GaN is very sensitive to the surface polishing even the minute unevenness in GaN substrate. Our expts. also indicated that a low initial growth rate was necessary to obtain high-cryst.-quality epitaxial m-plane GaN. In contrast, high-cryst.-quality a-plane GaN was obtained even with a high initial growth rate, indicating that the cryst. quality of a-plane GaN is not sensitive to surface roughness.

  331. Nonpolar a-plane AlGaN/GaN heterostructure field-effect transistors grown on freestanding GaN substrate 査読有り

    Isobe, Yasuhiro; Ikki, Hiromichi; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Sugiyama, Takayuki; Amano, Hiroshi; Imade, Mamoru; et al

    Applied Physics Express   4 巻 ( 6 ) 頁: 064102/1-064102/3   2011年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We fabricated and characterized nonpolar a-plane AlGaN/GaN heterostructure field-effect transistors (HFETs) grown on an a-plane freestanding GaN substrate. By optimizing the growth conditions, the unintentionally doped oxygen concn. was much reduced in the a-plane GaN buffer layer. As a result, the low leakage current in the buffer layer was realized without doping of deep acceptors, such as Fe and C, by which an impurity-contamination-free channel layer can be successfully grown.

  332. Partial strain relaxation by stacking fault generation in InGaN multiple quantum wells grown on (1-101) semipolar GaN 査読有り

    Wu, Z. H.; Tanikawa, T.; Murase, T.; Fang, Y.-Y.; Chen, C. Q.; Honda, Y.; Yamaguchi, M.; Amano, H.; Sawaki, N.

    Applied Physics Letters   98 巻 ( 5 ) 頁: 051902/1-051902/3   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The authors have studied the structural properties and relaxation phenomenon of InGaN multiple quantum wells (QWs) on (1.hivin.101) semipolar GaN templates grown on patterned (001) Si substrates by selective area growth technique. Studies by TEM and x-ray diffraction reciprocal space mapping reveal that QWs emitting light at 540 nm experience significant strain relaxation along the in-plane [1.hivin.10.hivin.2] direction by the generation of an array of basal stacking faults (BSF). The generation of BSFs in 540 nm QWs could be an important factor limiting its luminescence efficiency.

  333. Effect of lateral vapor phase diffusion during the selective growth of InGaN/GaN MQW on semipolar and nonpolar GaN stripes 査読有り

    Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    Physica Status Solidi A   208 巻 ( 5 ) 頁: 1175-1178   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated the InGaN/GaN multiple quantum well (MQW) thickness and cathode luminescence (CL) distribution on nonpolar (11-20)GaN, semipolar (11-22)GaN, and (1-101)GaN microstripes grown by selective metal-org. vapor phase epitaxy (MOVPE) on patterned Si substrates. All samples exhibited ridge growth. To clarify the effect of vapor phase diffusion, the two-dimensional diffusion equation was solved. The results were in good agreement with the thickness distribution on the (11-20)GaN stripe when we assumed D/k0 to be 1 μm. However, the results were not in agreement for the semipolar case. On the semipolar face, the surface migration length might be greater, thus increasing the thickness nonuniformity. CL anal. indicated a uniform indium compn. on the (11-20) and (11-22) faces. On the (1-101)GaN stripe, the indium compn. decreased near the (0001) edge. Excess Ga is considered to affect the compositional nonuniformity on the (1-101) facet.

  334. Evidence for moving of threading dislocations during the VPE growth in GaN thin layers 査読有り

    Kuwano, Noriyuki; Miyake, Hideto; Hiramatsu, Kazumasa; Amano, Hiroshi; Akasaki, Isamu

    Physica Status Solidi C   8 巻 ( 5 ) 頁: 1487-1490.   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Cross-sectional transmission electron microscope (TEM) observation was performed in detail to analyze the morphol. of threading dislocations (TDs) in GaN thin layers with various thicknesses. The GaN layers were overgrown on an Al0.28Ga0.72N layer by the metal-org. vapor-phase epitaxy (MOVPE) method. In a GaN layer about 50 nm in thickness, TDs running up in the AlGaN layer pass into the GaN layer and most of them reach the top surface without bending. In thicker GaN layers, on the other hand, many of TDs form a hairpin-configuration on or above the interface of GaN and AlGaN to be annihilated. This difference in morphol. of TDs indicates that the TDs have moved down inside the GaN layer. Since the formation of hairpins is attributed to a stress-relief, there should be an extra half-plane between the paired TDs. Therefore, the movement of TDs should be of "climb motion". Another example of possible TD movement inside a GaN layer is also described. It is emphasized that the possibility of TD-movements inside the thin film crystal during the growth should be taken into account in anal. of thin-layer growth through the behavior of TDs.

  335. Growth of AlGaN/GaN heterostructure on vicinal m-plane free-standing GaN substrates prepared by the Na flux method 査読有り

    Isobe, Yasuhiro; Iida, Daisuke; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Imade, Mamoru; Kitaoka, Yasuo; et al

    Physica Status Solidi A   208 巻 ( 5 ) 頁: 1191-1194   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We fabricated and characterized AlGaN/GaN heterostructure growth by MOVPE on vicinal m-plane free-standing GaN substrates prepd. by the Na flux method. The miscut angle in the LPE-GaN substrate has a great influence on the surface morphol. and cryst. quality of epitaxial GaN and AlGaN films. In particular, AlGaN/GaN on a 4° miscut-angle LPE-GaN substrate shows large step bunching, small-miscut-angle LPE GaN substrate is essential for fabricating on FET structure with a flat surface.

  336. Internal quantum efficiency of whole-composition-range AlGaN multiquantum wells 査読有り

    Ban, Kazuhito; Yamamoto, Jun-ichi; Takeda, Kenichiro; Ide, Kimiyasu; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Applied Physics Express   4 巻 ( 5 ) 頁: 052101/1-052101/3   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We analyze the internal quantum efficiency (IQE) of whole-compn.-range AlGaN multiquantum wells (MQWs) on AlGaN with various dislocation densities (DDs) by excitation-d.-dependent photoluminescence measurement. IQEs of deep UV/UV (DUV/UV) MQWs are strongly dependent on the DD. IQE with an excess carrier d. of 1 × 1018 cm-3 changes from 4 to 64% when the DD changes from 6 × 109 to 2 × 108 cm-2. This trend is almost the same for DUV/UV MQWs with emission wavelength ranging from 230 to 350 nm. Thus, the redn. of the DD is very important for the realization of a high-IQE DUV/UV active layer.

  337. Microstructural analysis of thick AlGaN epilayers using Mg-doped AlN underlying layer 査読有り

    Nonaka, K.; Asai, T.; Ban, K.; Yamamoto, J.; Iwaya, M.; Takeuchi, T.; Kamiyama, S.; Akasaki, I.; Amano, H.; Wu, Z. H.

    Physica Status Solidi C   8 巻 ( 5 ) 頁: 1467-1470   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This paper reports the microstructural anal. of 20-μm-thick Al0.5Ga0.5N with improved cryst. quality owing to the use of a Mg-doped AlN underlying layer. The threading dislocation d. in 20-μm-thick Al0.5Ga0.5N on Mg-doped AlN was 8.6 × 108 cm-2, which is about one-fifth lower than that of Al0.5Ga0.5N on an undoped AlN underlying layer. The microstructural anal. was carried out to clarify dislocation behaviors in the Al0.5Ga0.5N layer on the Mg-doped AlN underlying layer.

  338. Freestanding highly crystalline single crystal AlN substrates grown by a novel closed sublimation method 査読有り

    Yamakawa, Masayasu; Murata, Kazuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Azuma, Masanobu

    Applied Physics Express   4 巻 ( 4 ) 頁: 045503/1-045503/3   2011年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We fabricated thick freestanding AlN films by a novel close-spaced sublimation method. The spacing between a sintered AlN polycrystal and a SiC substrate is 1 mm. A Ta ring was used to control the spacing between the AlN polycrystal and the SiC substrate. In addn., a special AlN adhesive was also used to fill in the gap between the AlN polycrystal, the Ta ring, and the SiC substrate. By a combination of these techniques, an AlN growth rate as high as 600 μm/h was achieved. A freestanding AlN layer was obtained by the sublimation of the SiC substrate during the AlN growth.

  339. Spontaneous formation of highly regular superlattice structure in InGaN epilayers grown by molecular beam epitaxy 査読有り

    Wu, Z. H.; Kawai, Y.; Fang, Y.-Y.; Chen, C. Q.; Kondo, H.; Hori, M.; Honda, Y.; Yamaguchi, M.; Amano, H.

    Applied Physics Letters   98 巻 ( 14 ) 頁: 141905/1-141905/3   2011年3月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Structural properties of thick InGaN layers grown on GaN by plasma-assisted mol. beam epitaxy using two growth rates of 1.0 and 3.6 Å/s have been investigated. A highly regular superlattice (SL) structure formed spontaneously in the film grown at 3.6 Å/s but not in the film grown at 1.0 Å/s. The faster grown film also exhibited superior structural quality, which could be due to the surface roughness suppression caused by kinetic limitation, and the inhibition of the Frank-Read dislocation generation mechanism within the spontaneously formed SL structure.

  340. Demonstration of diamond field effect transistors by AlN/diamond heterostructure 査読有り

    Imura, Masataka; Hayakawa, Ryoma; Watanabe, Ei-Ichiro; Liao, Mei-Yong; Koide, Yasuo; Amano, Hiroshi

    Physica Status Solidi RRL:   5 巻 ( 3 ) 頁: 125-127.   2011年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This is the first report on an AlN/diamond heterojunction field effect transistor (HFET). The AlN epilayer is grown on oxygen-terminated (111) diamond substrates using metalorg. vapor phase epitaxy at a temp. as high as 1240 °C. The transistor and gate capacitance-voltage characteristics indicate that the HFET behaves as a p-channel FET with a normally-on depletion mode. The HFET channel is located at the AlN/diamond interface, and holes are accumulated in diamond close to the interface. The development of the AlN/diamond HFET creates a new possibility for diamond-based power electronics.

  341. Role of nonradiative recombination centers and extended defects in nonpolar GaN on light emission efficiency 査読有り

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Amano, H.; Pearton, S. J.; Lee, I.-H.; Sun, Q.; Han, J.; Karpov, S. Yu.

    Applied Physics Letters   98 巻 ( 7 ) 頁: 072104/1-072104/3   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The correlation of integrated microcathodoluminescence efficiency with cryst. quality and deep trap d. of nonpolar GaN films grown by metal org. CVD on semi-insulating 6H-m-SiC or r-sapphire is analyzed. The results suggest a strong influence of nonradiative recombination centers whose concn. decreases with decreased d. of extended defects. Electron traps with energy levels at Ec-0.6 eV and which pin the Fermi level in films with high defect d. are the most likely candidates for the decrease in light emission efficiency in nonpolar GaN.

  342. GaInN-based solar cells using strained-layer GaInN/GaInN superlattice active layer on a freestanding GaN substrate 査読有り

    Kuwahara, Yousuke; Fujii, Takahiro; Sugiyama, Toru; Iida, Daisuke; Isobe, Yasuhiro; Fujiyama, Yasuharu; Morita, Yoshiki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi, Amano Hiroshi; et al

    Applied Physics Express   4 巻 ( 2 ) 頁: 021001/1-021001/3   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    High-performance GaInN-based solar cells with high open-circuit voltage, high short-circuit c.d., and good fill factor have been obtained using a combination of two different GaInN superlattice structures. The GaInN barrier thicknesses (3 and 0.6 nm) in both superlattice structures were optimized, resulting in a thick GaInN-based active layer with a low pit d. in the device. The conversion efficiency is 2.5% under a solar simulator of air-mass 1.5G and an irradn. intensity of 155 mW/cm2.

  343. Internal quantum efficiency and internal loss of ultraviolet laser diodes on the low dislocation density AlGaN underlying layer 査読有り

    Takeda, Kenichiro; Nagata, Kengo; Ichikawa, Tomoki; Nonaka, Kentaro; Ogiso, Yuji; Oshimura, Yoshinori; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; et al

    Physica Status Solidi C   8 巻 ( 2 ) 頁: 464-466   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We fabricated and evaluated GaN/AlGaN multi-quantum wells (MQWs) and UV laser diodes (UV LDs) on high and low dislocation d. underlying layers by epitaxial lateral overgrowth (ELO) method. We analyzed the internal quantum efficiency (IQE) vs. carrier concn. characteristics quant. by excitation intensity dependent photoluminescence method. The IQE of the MQWs on the ELO AlGaN is 75% when the carrier d. is 1 × 1019 cm-3. We demonstrated the UV LD on the ELO AlGaN. However, the UV LD on flat AlGaN did not operate. Also, we investigated the internal loss (α1) and the IQE multiplied the injection efficiency by changing the reflectivity of the facets. The results showed that the internal loss is 6 cm-1, and the IQE multiplied by the injection efficiency is 18%

  344. Microstructures of GaInN/GaInN superlattices on GaN substrates 査読有り

    Sugiyama, Toru; Kuwahara, Yosuke; Isobe, Yasuhiro; Fujii, Takahiro; Nonaka, Kentaro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Applied Physics Express   4 巻 ( 1 ) 頁: 015701/1-015701/3.   2011年1月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We found different behaviors of misfit dislocations in a Ga0.83In0.17N single layer and in Ga0.83In0.17N/Ga0.93In0.07N superlattices, both on GaN substrates. In the case of the single layer, misfit dislocations were formed at the GaInN/GaN interfaces and extended through the GaInN layer to the surface. In contrast, the misfit dislocations in the superlattices are bent laterally at interfaces between the Ga0.83In0.17N and Ga0.93In0.07N layers. In addn., most of the dislocations do not reach the surface owing to the formation of dislocation loops. As a result, the dislocation d. at the surface of the GaInN superlattice sample was 5 × 107 cm-2.

  345. Drastic reduction of dislocation density in semipolar (11-.22) GaN stripe crystal on Si substrate by dual selective metal-organic vapor phase epitaxy 査読有り

    Murase, Tasuku; Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi; Sawaki, Nobuhiko

    Japanese Journal of Applied Physics   50 巻 ( 1 ) 頁: 01AD04/1-01AD04/3.   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A drastic redn. of the dislocation d. in a semipolar (11.hivin.22) GaN stripe on a patterned Si substrate was achieved by the 2-step selective growth of a GaN stripe. After depositing a SiO2 mask on the (11.hivin.22) and (000.hivin.1) faces of a GaN stripe grown on a (113) Si substrate, GaN was regrown only on the (.hivin.1.hivin.122) face. The dislocation d. estd. from the dark-spot d. in a cathodoluminescence (CL) image greatly decreased from 4.0 × 108 to 1.0 × 105/cm2 in the regrowth region. A TEM image also verified that there were no dislocations at the regrowth interfaces.

  346. High-temperature operation of normally off-mode AlGaN/GaN heterostructure field-effect transistors with p-GaN gate 査読有り

    Sugiyama, Takayuki; Amano, Hiroshi; Iida, Daisuke; Iwaya, Motoaki; Kamiyama, Satoshi; Akasaki, Isamu

    Japanese Journal of Applied Physics   50 巻 ( 1 ) 頁: 01AD03/1-01AD03/3   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We demonstrated the high-temp. operation of normally off-mode heterostructure field-effect transistors (HFETs) with a p-GaN gate. The HFETs with a p-GaN gate were operated in the normally off mode at 350 °C. The temperture dependence of their performance was compared with the results of simulation.

  347. MBE-VLS growth of catalyst-free III-V axial heterostructure nanowires on (1 1 1)Si substrates 査読有り

    Paek, Jihyun; Yamaguchi, Masahito; Amano, Hiroshi

    Journal of Crystal Growth   323 巻 ( 1 ) 頁: 315-318   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    For application in novel opto-electronic nanowire devices, Ga-assisted GaAs/InxGa1-xAs axial heterostructure nanowires grown on a (1 1 1)Si substrate at a high In/Ga flux ratio were investigated. The increased diam. of the InxGa1-xAs region of the nanowire was obsd. from a SEM image. The In compn. of 0.01-0.02 of the InxGa1-xAs was shown by EDX point anal. The In concn. of 0.62 of an In-Ga alloy droplet was estd. from the diam. ratio of the InxGa1-xAs/GaAs region. From these results, it was considered that the excess In was collected in the droplet, resulting in an increased nanowire diam. The increased diam. of the InxGa1-xAs region was also discussed together with the results of thermodn. calcn.

  348. Realization of nitride-based solar cell on freestanding GaN substrate 査読有り

    Kuwahara, Yosuke; Fujii, Takahiro; Fujiyama, Yasuharu; Sugiyama, Tohru; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

    Applied Physics Express   3 巻 ( 11 ) 頁: 111001/1-111001/3   2010年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A p-i-n solar cell composed of an undoped GaInN layer sandwiched between n- and p-type GaN layers was grown on a freestanding c-plane GaN substrate and a c-plane sapphire substrate covered with a low-temp.-deposited buffer layer. The open-circuit voltage is 2.23 V, the fill factor is 61%, the short-circuit c.d. is 1.59 mA/cm2, and the conversion efficiency of the solar cell on the GaN substrate is 1.41% using a solar simulator (1.5 suns). Compared with the solar cell characteristics of the device grown on the sapphire substrate, pit d. markedly decreases. As a result, shunt resistance increases, suppressing the open-circuit voltage drop.

  349. Strain relaxation mechanisms in AlGaN epitaxy on AlN templates 査読有り

    Wu, Zhihao; Nonaka, Kentaro; Kawal, Yohjiro; Asai, Toshiaki; Ponce, Fernando A.; Chen, Changqing; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu

    Applied Physics Express   3 巻 ( 11 ) 頁: 111003/1-111003/3   2010年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Two strain relaxation processes have been obsd. in AGaN layers grown on thick AlN templates. In Process I, a type threading dislocations (TDs) with b = 1/3.ltbbrac.11.hivin.20.rtbbrac. from the AlN underlayer are inclined away from the [0001] axis toward the .ltbbrac.1.hivin.100.rtbbrac. directions when they enter the AlGaN film, forming dislocation line projection perpendicular to the Burger vector. In Process II, a + c-type TDs from the AlN underlayer with Burgers vector of b = 1/3.ltbbrac.11.hivin.23.rtbbrac. glide on {0.hivin.111} planes when they enter the AlGaN film to generate interfacial misfit dislocations lying along the .ltbbrac..hivin.2110.rtbbrac. directions at the AlGaN/AlN interface.

  350. Temperature dependence of normally off mode AlGaN/GaN heterostructure field-effect transistors with p-GaN gate 査読有り

    Sugiyama, Takayuki; Iida, Daisuke; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu

    Physica Status Solidi C:   7 巻 ( 10 ) 頁: 2419-2422   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We demonstrated high-temp. operation of normally off-mode junction-heterostructure-field-effect transistors (JHFETs) with a p-GaN gate that shows a very small shift of the threshold voltage against ambient temp. Distinct normally off-mode operation with a max. drain current of 93.2 mA/mm at 300 °C was realized. Therefore, normally off-mode GaN-based JFETs are greatly superior to Si-based devices as high-temp. switching devices.

  351. Analysis of polar direction of AlN grown on (0001) sapphire and 6H-SiC substrates by high-temperature metal-organic vapor phase epitaxy using coaxial impact collision ion scattering spectroscopy 査読有り

    Imura, Masataka; Ohnishi, Tsuyoshi; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Amano, Hiroshi; Lippmaa, Mikk

    Physica Status Solidi C   7 巻 ( 10 ) 頁: 2365-2367   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    High-cryst. quality AlN layers with an atomically flat surface are grown on (0001) sapphire and 6H-SiC substrates by metal-org. vapor phase epitaxy at 1400 °C without low-temp. buffer layer. The polar direction of AlN layers is investigated by coaxial impact-collision ion scattering spectroscopy (CAICISS). For AlN growth on sapphire substrate, trimethylaluminum (TMAI) is supplied for 10 s before introducing ammonia (NH3). For AlN growth on SiC substrate, TMAl and NH3 are supplied at the same time. The CAICISS spectrum of AlN layers is analyzed by measuring the dependence of the Al atoms signal intensity on the angle of ion beam incidence considering the shadowing and focusing effects for detg. the polar direction of AlN layers. The CAICISS spectra clearly indicate the polar direction of AlN layers and both AlN layers are found to be had the Al-polarity.

  352. Atomic layer epitaxy of AlGaN 査読有り

    Nagamatsu, Kentaro; Iida, Daisuke; Takeda, Kenichiro; Nagata, Kensuke; Asai, Toshiaki; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu

    Physica Status Solidi C:   7 巻 ( 10 ) 頁: 2368-2370   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Atomic layer epitaxy of AlGaN with an av. growth rate of as high as 4.5 mm/h has been achieved by the high-speed switching-valves (HSSVs) technique in a raised-pressure metalorg. vapor phase epitaxy system. Regarding the duration of group III metalorgs. and NH3 gases input, 0.1 s for each injection time is found to be sufficient to realize AlGaN growth of one monolayer per cycle over a 2-in. wafer with hydrogen and nitrogen carrier gases at a raised pressure. Low-temp. growth of high-quality AlGaN has been achieved using HSSVs.

  353. GaInN/GaN p-i-n light-emitting solar cells 査読有り

    Fujiyama, Y.; Kuwahara, Y.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I.

    Physica Status Solidi C   7 巻 ( 10 ) 頁: 2382-2385.   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    GaInN/GaN p-i-n double-heterojunction structures were grown by metal-org. vapor phase epitaxy on c-plane sapphire substrates, and light-emitting solar cells with different GaInN active layer thicknesses were fabricated. The thickness of the GaInN active layer was varied from 100 to 400 nm, while the thickness of both n-type and p-type GaN layers was kept const. A semitransparent ohmic contact to p-type GaN was formed by electron-beam evapn. of Ni/Au (5 nm/5 nm). The film thickness of p-GaN was 50 nm. The external quantum efficiency (EQE) of the device with a 400 nm GaInN layer exceeded 60% at a wavelength of approx. 380 nm. The transparency of the Ni/Au electrode was 68%. Therefore, the internal quantum efficiency of this device exceeded 95%. Note that this device emitted green light when a forward voltage was applied. The electroluminescence peak wavelength was approx. 525 nm, which was much longer than the EQE peak wavelength. The origin of this large emission shift is discussed.

  354. Threshold voltage control using SiNx in normally off AlGaN/GaN HFET with p-GaN gate 査読有り

    Sugiyama, T.; Iida, D.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I.

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 1980-1982   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The threshold voltage (Vth) of normally off-mode AlGaN/GaN junction heterostructure field-effect transistors with a p-type GaN gate can be successfully controlled by inserting a SiNx insulator between the p-GaN and a Ni/Au electrode. The Vth can be controlled from +1 V to above +8 V. Moreover, the gate leakage current of transistors decreases and their gate voltage at which gate current steeply increases becomes higher. The mechanism of the threshold voltage change is analyzed by the equiv. circuit model.

  355. AlGaN/GaN HFETs on Fe-doped GaN substrates 査読有り

    Oshimura, Yoshinori; Takeda, Kenichiro; Sugiyama, Takayuki; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu; Bandoh, Akira; Udagawa, Takashi

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 1974-1976   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    AlGaN/GaN HFETs with different undoped GaN thicknesses were grown on Fe-doped freestanding GaN substrates by conventional MOVPE. To realize a high drain current, thick undoped GaN is found to be necessary. SIMS measurement shows that Fe is redistributed into the epilayer, by which the scattering center is generated at the channel when the thickness of the undoped GaN is insufficient. We also obsd. a similar Fe profile in the GaN/sapphire template placed on the side of the Fe-doped GaN substrate during growth. Therefore, Fe in the Fe-doped GaN substrate is redistributed not only through a solid but also through vapor.

  356. Growth and characterization of GaN grown on moth-eye patterned sapphire substrates 査読有り

    Ishihara, Akihiro; Kawai, Ryousuke; Kitano, Thukasa; Suzuki, Atushi; Kondo, Toshiyuki; Iwaya, Motoaki; Amano, Hiroshi; Kamiyama, Satoshi; Akasaki, Isamu

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 2056-2058   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To realize high-efficiency light-emitting diodes (LEDs), it is necessary to increase light extn. efficiency. Therefore, the introduction of a moth-eye structure, which consists of periodic cones with a pitch of optical wavelength magnitude, into a sapphire surface before the epitaxial growth of nitride films is very promising for reducing the reflectivity of light resulting in high light extn. efficiency. 450 nm GaInN/GaN LEDs were fabricated on conventional and moth-eye substrates by metal org. vapor phase epitaxy (MOVPE). The intensity of room-temp. photoluminescence emitted from the LED with the moth-eye-patterned sapphire substrate was 1.6 times higher than that emitted from the LED without the moth-eye substrate. Under a current injection of 50 mA, the output power of the moth-eye LED is 3.6 times higher than that of the conventional LED.
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  357. Growth of GaInN by raised-pressure metalorganic vapor phase epitaxy 査読有り

    Iida, Daisuke; Nagata, Kensuke; Makino, Takafumi; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu; Bandoh, Akira; Udagawa, Takashi

    Applied Physics Express   3 巻 ( 7 ) 頁: 075601/1-075601/2   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  358. Growth of low-dislocation-density AlGaN using Mg-doped AlN underlying layer 査読有り

    Asai, T.; Nonaka, K.; Ban, K.; Nagata, K.; Nagamatsu, K.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I.

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 2101-2103   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on a new technol. for growing low-dislocation-d. AlGaN in which a Mg-doped AlN underlying layer is used. By growing AlxGa1-xN on AlN:Mg with AlN molar fractions x of 0.3, 0.5 and 0.7, the d. of misfit dislocations is much reduced compared with that in the case of growing AlGaN on undoped AlN. In addn., the surface becomes atomically flat.

  359. Internal quantum efficiency of GaN/AlGaN-based multi quantum wells on different dislocation densities underlying layers 査読有り

    Takeda, Kenichiro; Mori, Fumiaki; Ogiso, Yuji; Ichikawa, Tomoaki; Nonaka, Kentaro; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 1916-1918   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Internal quantum efficiency (IQE) of GaN/AlGaN multi quantum wells on the low dislocation d. Al0.25Ga0.75N grown by epitaxial lateral overgrowth (ELO) and facet controlled epitaxial lateral overgrowth were investigated by excitation intensity dependent photoluminescence measurement. The threading dislocation d. decreased from 4 × 109cm-2 to 2 × 108 cm-2 by using ELO method, then the IQE was much improved from 5% to 40% when the carrier d. was 1 × 1018 cm-3.

  360. Mg-related acceptors in GaN 査読有り

    Monemar, B.; Paskov, P. P.; Pozina, G.; Hemmingsson, C.; Bergman, J. P.; Amano, H.; Akasaki, I.; Figge, S.; Hommel, D.; et al.

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 1850-1852   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Photoluminescence spectra of c-plane Mg doped GaN samples grown by MOVPE on bulk GaN templates reveal previously unknown properties, like the presence of several Mg-related acceptors. The use of unstrained samples allows a study of both bound exciton (BE) and donor-acceptor pair (DAP) spectra. Two main acceptors A1 and A2 are obsd. strongly in BE spectra as well as in DAP spectra, they have similar binding energies, i.e. about 220 meV. The common assignment of the deeper blue PL emission at 2.8-3.0 eV to a deep donor-shallow acceptor transition is questioned, and discussed in connection with the compensation problem in p-GaN. It seems like the Fermi level in p-GaN is controlled by a set of Mg-related acceptors at energies 0.2-0.6 eV from the valence band top.

  361. Nitride-based light-emitting solar cell 査読有り

    Kuwahara, Y.; Fujiyama Y; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 1807-1809   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the characteristics of a group-III-nitride-based solar cell. A GaInN/GaN double heterojunction p-i-n solar cell composed of a GaInN active layer sandwiched between n-type and p-type GaN layers was grown by metal-org. vapor phase epitaxy through an undoped GaN layer on (0001) sapphire substrate. The InN molar fraction of the GaInN active layer was detd. to be 11% from a secondary ion mass spectrometry profile. The max. external quantum efficiency reached 65%, and the internal quantum efficiency was 95% or more. This device emitted light after forward current injection. The PL peak almost corresponded to the absorption edge. However, the electroluminescence (EL) peak was at the wavelength much longer than the absorption edge. The open-circuit voltage is 1.51 V, the fill factor is 52%, and the short-circuit c.d. is 1.6 mA/cm2.

  362. Study of two-dimensional electron gas in AlGaN channel HEMTs with high crystalline quality 査読有り

    Hashimoto, Shin; Akita, Katsushi; Tanabe, Tatsuya; Nakahata, Hideaki; Takeda, Kenichiro; Amano, Hiroshi

    Physica Status Solidi C   7 巻 ( 7-8 ) 頁: 1938-1940   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Epitaxial structures of AlGaN channel high electron mobility transistors (HEMTs) were grown on sapphire and AlN substrates. Redn. in the full width at half max. of X-ray rocking curve for (10-12) peak of the AlGaN channel layer owing to the redn. of threading dislocation densities resulted in a sharp decrease in the sheet resistance of 2-dimensional electron gas (2DEG). In the case of AlGaN channel HEMTs, it was found that improvement of the cryst. quality of AlGaN channel layers is essential to the redn. of the sheet resistance of 2DEG. The use of AlN substrates resulted in improved cryst. quality of the AlGaN layer and lower 2DEG resistance, suggesting the high potential of AlN substrates for AlGaN channel HEMTs.

  363. Improved efficiency of 255-280 nm AlGaN-based light-emitting diodes 査読有り

    Pernot, Cyril; Kim, Myunghee; Fukahori, Shinya; Inazu, Tetsuhiko; Fujita, Takehiko; Nagasawa, Yosuke; Hirano, Akira; Ippommatsu, Masamichi; Iwaya, Motoaki; Kamiyama, Satoshi,Hiroshi Amano et al

    Applied Physics Express   3 巻 ( 6 ) 頁: 061004/1-061004/3   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report on the fabrication and characterization of AlGaN-based deep UV light-emitting diodes (LEDs) with the emission wavelength ranging from 255-280 nm depending on the Al compn. of the active region. The LEDs were flip-chip bonded and achieved external quantum efficiencies of over 3% for all investigated wavelengths. Under cw operation, an output power of more than 1 mW at 10 mA was demonstrated. A moth-eye structure was fabricated on the back side of the Al2O3 substrate, and on-wafer output power measurement indicated a 1.5-fold improvement of light extn.

  364. Compensation effect of Mg-doped a- and c-plane GaN films grown by metalorganic vapor phase epitaxy 査読有り

    Iida, Daisuke; Tamura, Kenta; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu

    Journal of Crystal Growth   312 巻 ( 21 ) 頁: 3131-3135.   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The elec. and optical properties of Mg-doped a- and c-plane GaN films grown by MOVPE were systematically investigated. The photoluminescence spectra of Mg-doped a- and c-plane GaN films exhibit strong emissions related to deep donors when Mg doping concns. are above 1 × 1020 cm-3 and 5 × 1019 cm-3, resp. The elec. properties also indicate the existence of compensating donors because the hole concn. decreases at such high Mg doping concns. In addn., we estd. the ND/NA compensation ratio of a- and c-plane GaN by variable-temp. Hall effect measurement. The obtained results indicate that the compensation effect of the Mg-doped a-plane GaN films is lower than that of the Mg-doped c-plane GaN films.

  365. Misfit strain relaxation in m-plane epitaxy of InGaN on ZnO 査読有り

    Wu, Z. H.; Sun, K. W.; Wei, Q. Y.; Fischer, A. M.; Ponce, F. A.; Kawai, Y.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I.

    Applied Physics Letters   96 巻 ( 7 ) 頁: 071909/1-071909/3   2010年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The microstructure of m-plane InGaN epilayers grown on m-plane ZnO has been found to depend significantly on indium content in the range from 0.07 to 0.17, where anisotropic lattice mismatch between InGaN and ZnO results in decreasingly tensile and increasingly compressive stress along the a and c lattice axes. For indium content below 0.10, periodic arrays of misfit dislocations with a Burgers vector of 1/3[11-20] are obsd. parallel to the [0001] direction. For indium content above 0.12, generation of basal-plane stacking faults relieve the compressive stress along the 0001 direction. These characteristic mechanisms of strain relaxation should provide new approaches to engineer thick InGaN layers with reduced lattice misfit strain.

  366. Microstructure of AlN with two-domain structure on (001) diamond substrate grown by metal-organic vapor phase epitaxy 査読有り

    Imura, Masataka, Nakajima, Kiyomi, Liao, Meiyong, Koide, Yasuo, Amano, Hiroshi

    Diamond and Related Materials   19 巻 ( 0 ) 頁: 131-133   2010年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigate the microstructures of domain boundaries in an AlN layer grown on a (001) diamond substrate by metal-org. vapor phase epitaxy. The AlN layer has a two-domain structure with crystal orientation along either <112-0> AlN [named by AlNI domain] or <101-0> AlN [named by AlNII domain] parallel to [110] direction of diamond. The AlNI and AlNII domains are not atomically bonded at two-domain boundary from initial to final step of growth, while an edge-type dislocation is generated at single-domain boundary (SDB). In addn., an inversion AlNI domain [named by AlNI*] is randomly-ordered at the initial stage of the coalescence between the AlNI domains. The AlNI* is easily terminated with increasing the thickness of AlNI domain. The inversion domain boundary changes to the edge-type dislocation at the SDB with further growth, which reduces the defect d. in the AlNI domains.

  367. High-output-power AlGaN/GaN ultraviolet-light-emitting diodes by activation of Mg-doped p-type AlGaN in oxygen ambient 査読有り

    Nagata, Kengo, Ichikawa, Tomoki, Takeda, Kenichiro, Nagamatsu, Kentaro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Physica Status Solidi A:   207 巻 ( 0 ) 頁: 1393-1396   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  368. MOVPE法により成長したa面及びc面MgドープGaNにおける補償効果 査読有り

    飯田大輔、田村健太、岩谷素顕、天野浩、上山智、赤﨑勇

      312 巻 ( 21 ) 頁: 3131-3135   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  369. Defects in highly Mg-doped AlN 査読有り

    Nonaka, Kentaro, Asai, Toshiaki, Nagamatsu, Kentaro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Physica Status Solidi A   207 巻 ( 0 ) 頁: 1299-1301   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  370. Growth mechanism of c-axis-oriented AlN on (001) diamond substrates by metal-organic vapor phase epitaxy 査読有り

    Imura, Masataka, Nakajima, Kiyomi, Liao, Meiyong, Koide, Yasuo, Amano, Hiroshi

    Journal of Crystal Growth   312 巻 ( 0 ) 頁: 368-372   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  371. Growth mechanism of c-axis-oriented AlN on (111) diamond substrates by metal-organic vapor phase epitaxy 査読有り

    Imura, Masataka, Nakajima, Kiyomi, Liao, Meiyong, Koide, Yasuo, Amano, Hiroshi

    Journal of Crystal Growth   312 巻 ( 0 ) 頁: 1325-1328   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  372. III族窒化物半導体へのp型ドーピングと結晶欠陥 招待有り 査読有り

    天野 浩、岩谷 素顕、上山 智、赤﨑 勇

    日本結晶成長学会誌   36 巻 ( 3 ) 頁: 200-204   2009年3月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    GaNおよびAlGaNにおけるMgアクセプタの挙動の詳細を明らかにした。

  373. Temperature dependence of excitonic transitions in a-plane AlN epitaxial layers 査読有り

    Murotani, Hideaki, Kuronaka, Takahiro, Yamada, Yoichi, Taguchi, Tsunemasa, Okada, Narihito, Amano, Hiroshi

    Journal of Applied Physics   105 巻 ( 0 ) 頁: 083533/1-083533/6   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  374. Activation energy of Mg in a-plane Ga1-xInxN (0 < x < 0.17) 査読有り

    Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Physica Status Solidi B:   246 巻 ( 0 ) 頁: 1188-1190   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  375. Crystal growth and p-type conductivity control of AlGaN for high-efficiency nitride-based UV emitters 査読有り

    Mori, T., Nagamatsu, K., Nonaka, K., Takeda, K., Iwaya, M., Kamiyama, S., Amano, H., Akasaki, I.

    Physica Status Solidi C   6 巻 ( 0 ) 頁: 2621-2625   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  376. Electrical properties and deep traps spectra in undoped and Si-doped m-plane GaN films 査読有り

    Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Markov, A. V., Yugova, T. G., Petrova, E. A., Amano, H., Kawashima, T., Scherbatchev, K. D., Bublik, V. T.

    Journal of Applied Physics   105 巻 ( 0 ) 頁: 063708/1-063708/9   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  377. Electrical properties and deep traps spectra in undoped M-plane GaN films prepared by standard MOCVD and by selective lateral overgrowth 査読有り

    Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Markov, A. V., Yakimov, E. B., Vergeles, P. S., Amano, H., Kawashima, T.

    Journal of Crystal Growth   311 巻 ( 0 ) 頁: 2923-2925   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  378. Evidence for two Mg related acceptors in GaN 査読有り

    Monemar B, Paskov P P, Pozina G, Hemmingsson C, Bergman J P, Kawashima T, Amano H, Akasaki I, Paskova T, Figge S, et al

    Physical review letters   102 巻 ( 0 ) 頁: 235501/1-235501/4   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  379. Experimental and theoretical investigations of optical properties of GaN/AlGaN MQW nanostructures. Impact of built-in polarization fields 査読有り

    Esmaeili, M., Gholami, M., Haratizadeh, H., Monemar, B., Holtz, P. O., Kamiyama, S., Amano, H., Akasaki, I.

    Opto-Electronics Review   17 巻 ( 0 ) 頁: 293-299   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  380. Growth of thick GaInN on grooved (1011) GaN/(1012) 4H-SiC 査読有り

    Matsubara, Tetsuya, Senda, Ryota, Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Journal of Crystal Growth   311 巻 ( 0 ) 頁: 2926-2928   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  381. High-performance UV emitter grown on high-crystalline-quality AlGaN underlying layer 査読有り

    Tsuzuki, Hirotoshi, Mori, Fumiaki, Takeda, Kenichiro, Ichikawa, Tomoki, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu, Yoshida, Harumasa, Kuwabara, Masakazu, et al

    Physica Status Solidi A   206 巻 ( 0 ) 頁: 1199-1204   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  382. InGaN growth with various InN mole fractions on m-plane ZnO substrate by metalorganic vapor phase epitaxy 査読有り

    Kawai, Yohjiro, Ohsuka, Shinya, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Journal of Crystal Growth   311 巻 ( 0 ) 頁: 2929-2932   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  383. Misfit strain relaxation by stacking fault generation in InGaN quantum wells grown on m-plane GaN 査読有り

    Fischer, Alec M., Wu, Zhihao, Sun, Kewei, Wei, Qiyuan, Huang, Yu, Senda, Ryota, Iida, Daisuke, Iwaya, Motoaki, Amano, Hiroshi, Ponce, Fernando A.

    Applied Physics Express   2 巻 ( 0 ) 頁: 041002/1-041002/3   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  384. Novel UV devices on high-quality AlGaN using grooved underlying layer 査読有り

    Tsuzuki, Hirotoshi, Mori, Fumiaki, Takeda, Kenichiro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu, Yoshida, Harumasa, Kuwabara, Masakazu, Yamashita, Yoji, et al

    Journal of Crystal Growth   311 巻 ( 0 ) 頁: 2860-2863   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  385. One-sidewall-seeded epitaxial lateral overgrowth of a-plane GaN by metalorganic vapor-phase epitaxy 査読有り

    Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Journal of Crystal Growth   311 巻 ( 0 ) 頁: 2887-2890   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  386. Optimization of electrode configuration in large GaInN light-emitting diodes 査読有り

    Ochiai, Wataru, Kawai, Ryosuke, Suzuki, Atsushi, Iwaya, Motoaki, Amano, Hiroshi, Kamiyama, Satoshi, Akasaki, Isamu

    Physica Status Solidic   6 巻 ( 0 ) 頁: 1416-1419   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  387. Relaxation and recovery processes of AlxGa1-xN grown on AlN underlying layer 査読有り

    Asai, Toshiaki, Nagata, Kensuke, Mori, Toshiaki, Nagamatsu, Kentaro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Journal of Crystal Growth   311 巻 ( 0 ) 頁: 2850-2852   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  388. Strong emission from GaInN/GaN multiple quantum wells on high-crystalline-quality thick m-plane GaInN underlying layer on grooved GaN 査読有り

    Senda, Ryota, Matsubara, Tetsuya, Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Applied Physics Express   2 巻 ( 0 ) 頁: 061004/1-061004/3   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  389. Impact of high-temperature growth by metal-organic vapor phase epitaxy on microstructure of AlN on 6H-SiC substrates 査読有り

    Imura Masataka, Sugimura Hiroki, Okada Narihito, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Bandoh Akira

    J. Crystal Growth   310 巻 ( 0 ) 頁: 2308-2313   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  390. High-efficiency AlGaN-based UV light-emitting diode on laterally overgrown AlN 査読有り

    Nagamatsu Kentaro, Okada Narihito, Sugimura Hiroki, Tsuzuki Hirotoshi, Mori Fumiaki, Iida Kazuyoshi, Bando Akira, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu

    J. Crystal Growth   310 巻 ( 0 ) 頁: 2326-2329   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  391. AlN and AlGaN by MOVPE for UV light emitting devices 査読有り

    Amano, Hiroshi, Imura, Masataka, Iwaya, Motoaki, Kamiyama, Satoshi, Akasaki, Isamu

    Materials Science Forum   590 巻 ( 0 ) 頁: 175-210   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  392. Breakthroughs in improving crystal quality of GaN and invention of the p-n junction blue-light-emitting diode 査読有り

    Akasaki, Isamu, Amano, Hiroshi

    Japanese Journal of Applied Physics   47 巻 ( 0 ) 頁: 3781   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  393. Control of p-type conduction in a-plane Ga1-xInxN (0 < x < 0.10) grown on r-plane sapphire substrate by metalorganic vapor-phase epitaxy 査読有り

    Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Journal of Crystal Growth   310 巻 ( 0 ) 頁: 4996-4998   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  394. Control of stress and crystalline quality in GaInN films used for green emitters 査読有り

    Iwaya, Motoaki, Miura, Aya, Senda, Ryota, Nagai, Tetsuya, Kawashima, Takeshi, Iida, Daisuke, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Journal of Crystal Growth   310 巻 ( 0 ) 頁: 4920-4922   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  395. Dynamical study of the radiative recombination processes in GaN/AlGaN QWs 査読有り

    Sabooni, Mahmood, Esmaeili, Morteza, Haratizadeh, Hamid, Monemar, Bo, Amano, Hiroshi

    Journal of Materials Science: Materials in Electronics   19 巻 ( 0 ) 頁: S316-S318   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  396. Effect of annealing on metastable shallow acceptors in Mg-doped GaN layers grown on GaN substrates 査読有り

    Pozina, G., Hemmingsson, C., Paskov, P. P., Bergman, J. P., Monemar, B., Kawashima, T., Amano, H., Akasaki, I., Usui, A.

    Applied Physics Letters   92 巻 ( 0 ) 頁: 151904/1-151904/3   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  397. High hole concentration in Mg-doped a-plane Ga1-xInxN (0<x<0.30) grown on r-plane sapphire substrate by metalorganic vapor phase epitaxy 査読有り

    Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu

    Applied Physics Letters   93 巻 ( 0 ) 頁: 182108/1-182108/3   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  398. All MOVPE grown nitride-based LED having sub mm underlying GaN 査読有り

    Tanaka Y., Ando J., Iida D., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 3073-3075   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  399. Effect of c-plane sapphire misorientation on the growth of AlN by high-temperature MOVPE 査読有り

    Nagamatsu Kentaro, Okada Narihito, Kato Naofumi, Sumii Takafumi, Bandoh Akira, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 3048-3050   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  400. Improvement in crystalline quality of thick GaInN on m-plane 6H-SiC substrates using sidewall epitaxial lateral overgrowth 査読有り

    Senda Ryota, Miura Aya, Kawashima Takeshi, Iida Daisuke, Nagai Tetsuya, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 3045-3047   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  401. InGaN growth on ZnO (0001) substrate by metalorganic vapor phase epitaxy 査読有り

    Kawai Y., Ohsuka S., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 3023-3025   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  402. Realization of low-dislocation-density, smooth surface, and thick GaInN films on m-plane GaN templates 査読有り

    Miura Aya, Nagai Tetsuya, Senda Ryota, Kawashima Takeshi, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu.

    J. Crystal Growth   310 巻 ( 0 ) 頁: 3308-3312   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  403. Improvement in performance of m-plane GaInN light emitting diode grown on m-plane SiC by sidewall epitaxial lateral overgrowth 査読有り

    Kawashima T., Hayakawa T., Hayashi M., Nagai T., Iida D., Miura A., Kasamatsu Y., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 2145-2147   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  404. Optimization of underlying layer and the device structure for group-III-nitride-based UV emitters on sapphire 査読有り

    Iida K., Watanabe H., Takeda K., Mori F., Tsuzuki H., Yamashita Y., Iwaya M., Kamiyama S., Amano H., Akasaki I., Maruyama H., Takagi T., Bandoh A.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 2142-2144   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  405. High drain current and low on resistance normally-off-mode AlGaN/GaN junction HFETs with a p-type GaN gate contact. 査読有り

    Fujii T., Nakamura S., Mizuno K., Nega R., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 1906-1909   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  406. Nonpolar GaN layers grown by sidewall epitaxial lateral overgrowth. Optical evidences for a reduced stacking fault density 査読有り

    Paskov P. P., Monemar B., Iida D., Kawashima T., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 1768-1770   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  407. Microstructure of threading dislocations caused by grain boundaries in AlN on sapphire substrates 査読有り

    Imura M., Sugimura H., Okada N., Iwaya M., Kamiyama S., Amano H., Akasaki I., Bando A.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 1582-1584   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  408. Sidewall epitaxial lateral overgrowth of nonpolar a-plane GaN by metalorganic vapor phase epitaxy 査読有り

    Iida Daisuke, Kawashima Takeshi, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 1575-1578   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  409. Growth of high-quality thick AlGaN by high-temperature metalorganic vapor phase epitaxy 査読有り

    Kato Naofumi, Sato S., Sugimura H., Sumii T., Okada N., Imura M., Iwaya M., Kamiyama S., Amano H., Akasaki I., Maruyama H., Takagi T., Bandoh A.

    Physica Status Solidi C   5 巻 ( 0 ) 頁: 1559-1561   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  410. Effect of annealing on metastable shallow acceptors in Mg-doped GaN layers grown on GaN substrates 査読有り

    Pozina G., Hemmingsson C., Paskov P. P., Bergman J. P., Monemar B., Kawashima T., Amano H., Akasaki I., Usui A.

    Appl. Phys. Lett.   92 巻 ( 0 ) 頁: 151904/1-151904/3   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  411. Photoluminescence from highly excited AlN epitaxial layers. 査読有り

    Yamada Yoichi, Choi Kihyun, Shin Seungho, Murotani Hideaki, Taguchi Tsunemasa, Okada Narihito, Amano Hiroshi

    Appl. Phys. Lett.   92 巻 ( 0 ) 頁: 131912/1-131912/3   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  412. Solution growth of AlN single crystal using Cu solvent under atmospheric pressure nitrogen 査読有り

    Kamei K., Shirai Y., Tanaka T., Okada N., Yauchi A., Amano H..

    Physica Status Solidi C:   4 巻 ( 0 ) 頁: 2211-2214   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  413. Epitaxial lateral growth of m-plane GaN and Al0.18Ga0.82N on m-plane 4H-SiC and 6H-SiC substrates 査読有り

    Kawashima T., Nagai T., Iida D., Miura A., Okadome Y., Tsuchiya Y., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    J. Crystal Growth   298 巻 ( 0 ) 頁: 261-264   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  414. Epitaxial lateral overgrowth of AlN on trench-patterned AlN layers 査読有り

    Imura Masataka, Nakano Kiyotaka, Narita Gou, Fujimoto Naoki, Okada Narihito, Balakrishnan Krishnan, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Noro Tadashi, Takagi Takashi, Bandoh Akira.

    J. Crystal Growth   298 巻 ( 0 ) 頁: 257-260   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  415. High-speed growth of AlGaN having high-crystalline quality and smooth surface by high-temperature MOVPE 査読有り

    Kato N., Sato S., Sumii T., Fujimoto N., Okada N., Imura M., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Maruyama H., Noro T., Takagi T., Bandoh A.

    J. Crystal Growth   298 巻 ( 0 ) 頁: 215-218   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  416. Reduction in defect density over whole area of (1-100) m-plane GaN using one-sidewall seeded epitaxial lateral overgrowth. 査読有り

    Kawashima T., Nagai T., Iida D., Miura A., Okadome Y., Tsuchiya Y., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi B   244 巻 ( 0 ) 頁: 1848-1852   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  417. Crystallographic polarity and crystallinity characterization of polar and nonpolar GaN epitaxial films by X-ray diffraction analyses. 査読有り

    Inaba Katsuhiko, Amano Hiroshi.

    Physica Status Solidi B   244 巻 ( 0 ) 頁: 1775-1779   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  418. Optical observation of discrete well width fluctuations in wide band gap III-nitride quantum well 査読有り

    Haratizadeh H., Monemar B., Paskov Plamen P., Holtz Per Olof, Valcheva E., Persson P., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi B   244 巻 ( 0 ) 頁: 1727-1734   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  419. One-step lateral growth for reduction in defect density of a-plane GaN on r-sapphire substrate and its application in light emitters 査読有り

    Iida D., Miura A., Okadome Y., Tsuchiya Y., Kawashima T., Nagai T., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi A   204 巻 ( 0 ) 頁: 2005-2009   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  420. High-efficiency AlGaN based UV emitters grown on high-crystalline-quality AlGaN using grooved AlN layer on sapphire substrate 査読有り

    Iida K., Watanabe H., Takeda K., Nagai T., Sumii T., Nagamatsu K., Kawashima T., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Bandoh A.

    Physica Status Solidi A   204 巻 ( 0 ) 頁: 2000-2004   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  421. Influence of well-width fluctuations on the electronic structure of GaN/AlxGa1-xN multiquantum wells with graded interfaces. 査読有り

    Valcheva E., Dimitrov S., Monemar B., Haratizadeh H., Persson P. O. A., Amano H., Akasaki I.

    Acta Physica Polonica, A   112 巻 ( 0 ) 頁: 395-400   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  422. Origin of localized excitons in In-containing three-dimensional bulk (Al,In,Ga)N alloy films probed by time-resolved photoluminescence and monoenergetic positron annihilation techniques 査読有り

    Chichibu S. F., Uedono A., Onuma T., Haskell B. A., Chakraborty A., Koyama T., Fini P. T., Keller S., Denbaars S. P., Speck J. S., Mishra U. K., Nakamura S., Yamaguchi S., Kamiyama S., Amano H., Akasaki I., Han J., Sota T.

    Philosophical Magazine   87 巻 ( 0 ) 頁: 2019-2039   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  423. Entirely crack-free ultraviolet GaN/AlGaN laser diodes grown on 2-in. Sapphire substrate. 査読有り

    Yoshida Harumasa, Takagi Yasufumi, Kuwabara Masakazu, Amano Hiroshi, Kan Hirofumi.

    Jpn. J. Appl. Phys.   46 巻 ( 0 ) 頁: 5782-5784   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  424. Influence of high temperature in the growth of low dislocation content AlN bridge layers on patterned 6H-SiC substrates by metalorganic vapor phase epitaxy 査読有り

    Balakrishnan Krishnan, Bandoh Akria, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu.

    Jpn. J. Appl. Phys.   46 巻 ( 0 ) 頁: L307-L310   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  425. Dislocations in AlN epilayers grown on sapphire substrate by high-temperature metal-organic vapor phase epitaxy 査読有り

    Imura Masataka, Nakano Kiyotaka, Fujimoto Naoki, Okada Narihito, Balakrishnan Krishnan, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Noro Tadashi, Takagi Takashi, Bandoh Akira.

    Jpn. J. Appl. Phys.   46 巻 ( 0 ) 頁: 1458-1462   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  426. Control of threshold voltage of enhancement-mode AlxGa1-xN/GaN junction heterostructure field-effect transistors using p-GaN gate contact 査読有り

    Fujii Takahiro, Tsuyukuchi Norio, Hirose Yoshikazu, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu.

    Jpn. J. Appl. Phys.   46 巻 ( 0 ) 頁: 115-118   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  427. Photoluminescence study of MOCVD-grown GaN/AlGaN MQW nanostructures: influence of Al composition and Si doping. 査読有り

    Esmaeili M., Haratizadeh H., Monemar B., Paskov P. P., Holtz P. O., Bergman P., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Nanotechnology   18 巻 ( 0 ) 頁: 025401/1-025401/6   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  428. Fabrication of enhancement-mode AlxGa1-xN/GaN junction heterostructure field-effect transistors with p-type GaN gate contact 査読有り

    Fujii T., Tsuyukuchi N., Hirose Y., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   4 巻 ( 0 ) 頁: 2708-2711   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  429. Microstructure of a-plane AlN grown on r-plane sapphire and on patterned AlN templates by metalorganic vapor phase epitaxy 査読有り

    Okada N., Imura M., Nagai T., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Maruyama H., Noro T., Takagi T., Bandoh A.

    Physica Status Solidi C   4 巻 ( 0 ) 頁: 2528-2531   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  430. Mg-doped high-quality AlxGa1-xN (x = 0-1) grown by high-temperature metal-organic vapor phase epitaxy 査読有り

    Imura M., Kato N., Okada N., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Noro T., Takagi T., Bandoh A.

    Physica Status Solidi C   4 巻 ( 0 ) 頁: 2502-2505   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  431. Void assisted dislocation reduction in AlN and AlGaN by high temperature MOVPE 査読有り

    Balakrishnan K., Iida K., Bandoh A., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica Status Solidi C   4 巻 ( 0 ) 頁: 2272-2276   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  432. Epitaxial lateral overgrowth of AlxGa1-xN (x>0.2) on sapphire and its application to UV-B-light-emitting devices 査読有り

    Iida Kazuyoshi, Kawashima Takeshi, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Bandoh Akira.

    J. Crystal Growth   298 巻 ( 0 ) 頁: 265-267   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  433. Metastable behavior of the UV luminescence in Mg-doped GaN layers grown on quasibulk GaN templates 査読有り

    Pozina G., Paskov P. P., Bergman J. P., Hemmingsson C., Hultman L., Monemar B., Amano H., Akasaki I., Usui A.

    Appl. Phys. Lett.   91 巻 ( 0 ) 頁: 221901/1-221901/3   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  434. Metastability of the UV luminescence in Mg-doped GaN layers grown by MOVPE on quasi-bulk GaN templates 査読有り

    Pozina G., Monemar B., Paskov P. P., Hemmingsson C., Hultman L., Amano H., Akasaki I., Paskova T., Figge S., Hommel D., Usui A.

    Physica B   401-402 巻 ( 0 ) 頁: 302-306   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  435. Realization of high-crystalline-quality thick m-plane GaInN film on 6H-SiC substrate by epitaxial lateral overgrowth 査読有り

    Senda Ryota, Miura Aya, Hayakawa Takemasa, Kawashima Takeshi, Iida Daisuke, Nagai Tetsuya, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu

    Jpn. J. Appl. Phys.   46 巻 ( 0 ) 頁: L948-L950   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  436. Dependence of DAP emission properties on impurity concentrations in N-/B-co-doped 6H-SiC. 査読有り

    Murata Satoshi, Nakamura Yoshihiro, Maeda Tomohiko, Shibata Yoko, Ikuta Mina, Sugiura Masaaki, Nitta Shugo, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Yoshimoto Masahiro, Furusho Tomoaki, Kinoshita Hiroyuki.

    Materials Science Forum   556-557 巻 ( 0 ) 頁: 335-338   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  437. Growth of high-quality and crack free AlN layers on sapphire substrate by multi-growth mode modification 査読有り

    Okada N., Kato N., Sato S., Sumii T., Nagai T., Fujimoto N., Imura M., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Maruyama H., Takagi T., Noro T., Bandoh A.

    J. Crystal Growth   298 巻 ( 0 ) 頁: 349-353   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  438. Microstructure in nonpolar m-plane GaN and AlGaN films 査読有り

    Nagai T., Kawashima T., Imura M., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    J. Crystal Growth   298 巻 ( 0 ) 頁: 288-292   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  439. Epitaxial lateral overgrowth of a-AlN layer on patterned a-AlN template by HT-MOVPE 査読有り

    Okada N., Kato N., Sato S., Sumii T., Fujimoto N., Imura M., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Takagi T., Noro T., Bandoh A.

    J. Crystal Growth   300 巻 ( 0 ) 頁: 141-144   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  440. Annihilation mechanism of threading dislocations in AlN grown by growth form modification method using V/III ratio 査読有り

    Imura Masataka, Fujimoto Naoki, Okada Narihito, Balakrishnan Krishnan, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Noro Tadashi, Takagi Takashi, Bandoh Akira.

    J. Crystal Growth   300 巻 ( 0 ) 頁: 136-140   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  441. Critical aspects of high temperature MOCVD growth of AlN epilayers on 6H-SiC substrates 査読有り

    Balakrishnan K., Fujimoto N., Kitano T., Bandoh A., Imura M., Nakano K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Takagi T., Noro T., Shimono K., Riemann T., Christen J.

    Physica Status Solidi C   3 巻 ( 0 ) 頁: 1392-1395   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  442. A hydrogen-related shallow donor in GaN? 査読有り

    Monemar B., Paskov P. P., Bergman J. P., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica B   376-377 巻 ( 0 ) 頁: 460-463   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  443. Dominant shallow acceptor enhanced by oxygen doping in GaN 査読有り

    Monemar B., Paskov P. P., Tuomisto F., Saarinen K., Iwaya M., Kamiyama S., Amano H., Akasaki I., Kimura S.

    Physica B   376-377 巻 ( 0 ) 頁: 440-443   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  444. Microstructure of nitrides grown on inclined c-plane sapphire and SiC substrate 査読有り

    Imura M., Honshio A., Miyake Y., Nakano K., Tsuchiya N., Tsuda M., Okadome Y., Balakrishnan K., Iwaya M., Kamiyama S., Amano H., Akasaki I.

    Physica B   376-377 巻 ( 0 ) 頁: 491-495   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  445. Dominant shallow acceptor enhanced by oxygen doping in GaN 査読有り

    Monemar B, Paskov P P, Tuomisto F, Saarinen K, Iwaya M, Kamiyama S, Amano H, Akasaki I, Kimura S

    Physica B   376-377 巻 ( 0 ) 頁: 440-443   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  446. 6H-SiC homoepitaxial growth and optical property of boron- and nitrogen-doped donor-acceptor pair (DAP) emission on 1° -off substrate by closed-space sublimation method 査読有り

    Kawai Y., Maeda T., Nakamura Y., Sakurai Y., Iwaya M., Kamiyama S., Amano H., Akasaki I., Yoshimoto M., Furusho T., Kinoshita H., Shiomi H.

    Materials Science Forum   527 巻 ( 0 ) 頁: 263-266   2006年