Updated on 2021/11/11

写真a

 
ISO Kenji
 
Organization
Institute of Materials and Systems for Sustainability MITSUBISHI CHEMICAL GaN Substrate Devices Industry-Academia Collaborative Chair Designated professor
Title
Designated professor

Degree 1

  1. Doctor of Philosophy ( 2017.9   Tokyo University of Agriculture and Technology ) 

Education 3

  1. Tokyo University of Agriculture and Technology

    2015.10 - 2017.9

  2. Tokyo Institute of Technology

    1999.4 - 2001.3

  3. Tokyo Institute of Technology

    1995.4 - 1999.3

 

Papers 32

  1. High quality GaN crystal grown by hydride vapor-phase epitaxy on SCAAT(TM) Reviewed

    Iso Kenji, Ikeda Hirotaka, Mochizuki Tae, Mikawa Yutaka, Izumisawa Satoru

    APPLIED PHYSICS EXPRESS   Vol. 13 ( 8 ) page: 085508   2020.8

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    Authorship:Lead author, Corresponding author   Language:Japanese  

    Web of Science

  2. Recent progress of large size and low dislocation bulk GaN growth Reviewed

    Mikawa Yutaka, Ishinabe Takayuki, Kagamitani Yuji, Mochizuki Tae, Ikeda Hirotaka, Iso Kenji, Takahashi Tatsuya, Kubota Kohei, Enatsu Yuuki, Tsukada Yusuke, Izumisawa Satoru

    GALLIUM NITRIDE MATERIALS AND DEVICES XV   Vol. 11280   page: 1128002   2020

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    Language:Japanese   Publisher:Proceedings of SPIE - The International Society for Optical Engineering  

    Large size and low dislocation density bulk gallium nitride (GaN) crystals were successfully grown by original acidic ammonothermal method SCAAT™ (Super Critical Acidic Ammonia Technology). It enabled us to obtain extremely high crystallinity true bulk GaN. In this article, 2-inch size non-polar m-plane GaN and nearly 4-inch size polar c-plane GaN were demonstrated. The dislocation and stacking fault density of m-plane GaN were in the range of 102 to 103 cm-2 and 0 to 5 cm-1, respectively. The full width at half maximum (FWHM) of X-ray rocking curve (XRC) on (10-12) plane was 6.4 arcsec. The dislocation density of c-plane GaN was in the range of 103 to 104 cm-2. The off-angle distribution of nearly 4-inch size c-plane GaN was ±0.006° in the span of 80 mm. The types of dislocations in the c-plane GaN were identified by transmission electron microscope (TEM) observation. Hydride vapor phase epitaxy (HVPE) growth on the SCAA™ c-plane seed was carried out and obtained 2-inch wafer. The crystallinity was comparable to SCAAT™ seed; FWHM of XRC was less than 10 arcsec and off-angle distribution was ±0.017°.

    DOI: 10.1117/12.2540737

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  3. Dislocation density reduction in (10(1)over-bar(1)over-bar) GaN at a high temperature using tri-halide vapor phase epitaxy Reviewed

    Iso Kenji, Ohtaki Shoma, Miyata Erina, Kido Yuka, Murakami Hisashi, Koukitu Akinori

    GALLIUM NITRIDE MATERIALS AND DEVICES XV   Vol. 11280   page: 1128009   2020

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Proceedings of SPIE - The International Society for Optical Engineering  

    The dependence of growth temperature for the epitaxial films grown by tri-halide vapor phase epitaxy (THVPE) on the crystal characteristics, such as the surface morphology, the full width at half maximum (FWHM), the threading dislocation density (TDD), the impurity concentration, and the photoluminescence (PL) was investigated. The epitaxial films grown at relatively high growth temperature of 1300-1350 °C showed that the crystal quality, such as FWHM and TDD retained that for the used substrate. The near-band-edge emission for PL for 1300-1350 °C growth showed lager intensities due to low nonradiative recombination center (NRC). Moreover, the epitaxial growth on the supercritical acidic ammonia technology (SCAAT™) substrate was demonstrated. The TDD was as low as 2 × 104 cm-2, which indicated that the epilayer grown by THVPE retained the superior crystal quality of SCAAT™.

    DOI: 10.1117/12.2543661

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  4. Thermal annealing effects on SCAAT substrate grown toward the c- and m-directions Reviewed

    Iso Kenji, Mikawa Yutaka, Ikeda Hirotaka, Hotta Kazuhiro, Mochizuki Tae, Izumisawa Satoru

    APPLIED PHYSICS EXPRESS   Vol. 12 ( 12 ) page: 125502   2019.12

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Applied Physics Express  

    The effect of the thermal annealing on an acidic ammonothermal gallium nitride (GaN) crystal grown toward the c- and m-directions was investigated. The specific annihilation of hydrogenated Ga vacancies was confirmed for the GaN crystal grown toward the m-direction but not for that grown toward the c-direction. A transparent and yellow luminescence-free ammonothermal GaN substrate was realized. The annihilation of the hydrogenated Ga vacancies was explained by the difference in the diffusion of F incorporated as a mineralizer between the c- and m-directions.

    DOI: 10.7567/1882-0786/ab5459

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  5. Growth of GaN on a three-dimensional SCAAT (TM) bulk seed by tri-halide vapor phase epitaxy using GaCl3 Reviewed

    Iso Kenji, Oozeki Daisuke, Ohtaki Syoma, Murakami Hisashi, Koukitu Akinori

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 58   page: SC1024   2019.6

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Japanese Journal of Applied Physics  

    GaN with a film thickness of 200-600 μm was grown on the as-grown three-dimensional supercritical acidic ammonia technology (SCAATTM) bulk seed that comprised only semipolar planes at a temperature as high as 1390 °C by tri-halide vapor phase epitaxy; further, the GaN film was also characterized. The FWHM value of the X-ray rocking curves was ∼40″, which was almost similar to the value of the used seed. The curvature radii were as large as 40-64 m. Further, the carrier concentrations were observed to be as small as 5.1 × 1017-9.1 × 1017 cm-3. However, the basal plane stacking fault densities were observed to be 3.4 × 101-5.4 × 101 cm-1 and were observed to increase during the growth process because of the as-grown SCAATTM seed surface condition.

    DOI: 10.7567/1347-4065/ab1479

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  6. Annihilation mechanism of V-shaped pits in c-GaN grown by hydride vapor-phase epitaxy Reviewed

    Iso Kenji, Ikeda Hirotaka, Gouda Riki, Mochizuki Tae, Izumisawa Satoru

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 58   page: SC1011   2019.6

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Japanese Journal of Applied Physics  

    An evident issue in performing GaN growth along the c-direction is the generation of V-shaped pits on its surface. Here, we investigated the transition of the angle of facets forming a V-shaped pit via three-photon excitation photoluminescence (3PPL). The intermittent doping of Ge was introduced to GaN growth to observe the growth front. The size of the V-shaped pit composed of {} facets decreased along the growth direction, whereas that composed of {} facets, increased. Furthermore, planar growths of c-GaN and semipolar GaN having various surface orientations revealed that the V-shaped pit composed of {} was likely to annihilate rather than that of {} under the growth condition of N2 carrier gas, which coincides with the result of 3PPL.

    DOI: 10.7567/1347-4065/ab0402

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  7. Dependence of surface morphology at initial growth of CdTe on the II/VI on (211) Si substrates by vapor phase epitaxy using metallic Cd source Reviewed

    Iso Kenji, Gokudan Yuya, Shiraishi Masumi, Nishikado Minae, Murakami Hisashi, Koukitu Akinori

    JOURNAL OF CRYSTAL GROWTH   Vol. 506   page: 185 - 189   2019.1

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Journal of Crystal Growth  

    The initial growth of CdTe having a thickness of 20–500 nm on (2 1 1) Si substrates was investigated to observe the growth of CdTe at the interface for hetero-epitaxial growth. The dependence of surface morphologies at the initial growth on the II/VI and the growth time was evaluated. The (1 3 3) surface orientation at the interface was shown in CdTe films grown on (2 1 1) Si substrates, which was irrespective of the II/VI. For a relatively high II/VI of 36, hillocks having a (2 1 1) orientation were observed on the underlayer having a (1 3 3) orientation. CdTe having a (2 1 1) orientation was dominant during the growth, due to its lateral coalescence on the underlayer. The dependence of the orientation between (1 3 3) and (2 1 1) CdTe films on (2 1 1) Si substrates on the II/VI was explained by the difference between the step-flow growth on the step and the spontaneous nucleation on the terrace.

    DOI: 10.1016/j.jcrysgro.2018.10.038

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  8. Vapor Phase Epitaxy of (133) and (211) CdTe on (211) Si Substrates Using Metallic Cd Source Reviewed

    Iso Kenji, Gokudan Yuya, Shiraishi Masumi, Nishikado Minae, Murakami Hisashi, Koukitu Akinori

    JOURNAL OF ELECTRONIC MATERIALS   Vol. 48 ( 1 ) page: 454 - 459   2019.1

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Journal of Electronic Materials  

    Single-crystalline CdTe films were grown in both (133) and (211) surface orientations on (211) Si substrates by vapor-phase epitaxy using metallic Cd source as a group-II precursor. The orientation of epitaxial films depended on the ratio of group-II and -VI precursors, i.e., II/VI. The orientation of epitaxial films was changed from (133) to (211) by increasing the II/VI under the CdTe growth condition. The surface morphology for (133) CdTe was smooth, whereas the surface for (211) CdTe was composed of hillocks with (111), (110), (101), and (100) facets. The full width at half maximum (FWHM) of the epitaxial films with the same thickness showed that the crystalline quality of (133) CdTe was better than that of (211) CdTe. The dependence of the orientation between (133) and (211) CdTe films on (211) Si substrates on the II/VI was explained by the difference between the step-flow growth on the step and the spontaneous nucleation on the terrace.

    DOI: 10.1007/s11664-018-6728-1

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  9. Direct Growth of CdTe on a (211) Si Substrate with Vapor Phase Epitaxy Using a Metallic Cd Source Reviewed

    Iso Kenji, Gokudan Yuya, Shiraishi Masumi, Murakami Hisashi, Koukitu Akinori

    JOURNAL OF ELECTRONIC MATERIALS   Vol. 46 ( 10 ) page: 5884 - 5888   2017.10

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Journal of Electronic Materials  

    We successfully performed epitaxial CdTe growth on a Si (211) substrate with vapor-phase epitaxy using a cost-effective metallic cadmium source as a group-II precursor. The thermodynamic data demonstrate that the combination of metallic Cd and diisopropyl-telluride (DiPTe) with a H2 carrier gas enables the growth of CdTe crystals. A CdTe single crystal with a (422) surface orientation was obtained when a growth temperature between 600°C and 650°C was employed. The surface morphology and crystalline quality were improved with increasing film thickness. The full-width at half-maximum of the x-ray rocking curves with a film thickness of 15.7 μm for the skew-symmetrical (422) and asymmetrical (111) reflection were 528 arcsec and 615 arcsec, respectively.

    DOI: 10.1007/s11664-017-5584-8

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  10. Quasiequilibrium crystal shape and kinetic Wulff plot for GaN grown by trihalide vapor phase epitaxy using GaCl3 Reviewed

    Iso Kenji, Matsuda Karen, Takekawa Nao, Murakami Hisashi, Koukitu Akinori

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   Vol. 254 ( 8 ) page: 1600679   2017.8

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Physica Status Solidi (B) Basic Research  

    We demonstrated the selective-area growth (SAG) of the nonpolar m-plane (Formula presented.) and the polar −c-plane (Formula presented.) substrates to determine the quasiequilibrium crystal shape (quasi-ECS) by trihalide vapor phase epitaxy (THVPE). The results were compared with those by hydride vapor phase epitaxy (HVPE). The polar N-face (Formula presented.) and the nonpolar m-planes (Formula presented.) were consistently stable with the semipolar planes (Formula presented.) emerging only at high temperature for the quasi-ECS grown by THVPE. The clear facets of the polar Ga-face (0001) and Ga-face sense semipolar planes such as (Formula presented.) did not appear. The kinetic Wulff plots for THVPE were constructed using the growth velocities for each emerging facet of the SAG. Bird's-eye view SEM images of the selective-area GaN crystals grown on the m-plane and –c-plane for THVPE.

    DOI: 10.1002/pssb.201600679

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  11. Thermodynamic analysis of vapor-phase epitaxy of CdTe using a metallic Cd source Reviewed

    Iso Kenji, Murakami Hisashi, Koukitu Akinori

    JOURNAL OF CRYSTAL GROWTH   Vol. 470   page: 122 - 127   2017.7

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Journal of Crystal Growth  

    Thermodynamic analysis of CdTe growth using cost-effective metallic Cd and dialkyl telluride was performed. The major vapor species at source zone in equilibrium were gaseous Cd for the group-II precursor, and Te2 and H2Te for the group-VI precursors. The driving force for the CdTe deposition was still positive even at 650 °C. This indicates that CdTe formation from gaseous Cd can proceed thermodynamically. Furthermore, the calculations showed that CdTe decomposes at higher temperature and increasing the II/VI ratio increases the limit of the growth temperature, which coincides with the experimental results.

    DOI: 10.1016/j.jcrysgro.2017.04.027

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  12. Thick nonpolar m-plane and semipolar (10(1)over-bar(1)over-bar) GaN on an ammonothermal seed by tri-halide vapor-phase epitaxy using GaCl3 Reviewed

    Iso Kenji, Matsuda Karen, Takekawa Nao, Hikida Kazuhiro, Hayashida Naoto, Murakami Hisashi, Koukitu Akinori

    JOURNAL OF CRYSTAL GROWTH   Vol. 461   page: 25 - 29   2017.3

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Journal of Crystal Growth  

    GaN layers of thickness 0.5–1.3 mm were grown at 1280 °C at a growth rate of 95–275 µm/h by tri-halide vapor-phase epitaxy on nonpolar m-plane (101̅0) and semipolar (101̅1̅) ammonothermal GaN substrates. For nonpolar m-plane (101̅0) with a −5° off-angle, the full widths at half maximum (FWHMs) of X-ray rocking curves (XRCs) and the basal plane stacking fault (BSF) density increased from 50 to 178″ and from 4.8×101 to 1.0×103 cm−1, respectively, upon increasing the growth rate from 115 to 245 µm/h. On the other hand, the XRC-FWHM and the BSF density for semipolar (101̅1̅) grown at 275 µm/h were as small as 28″ and 8.3×101 cm−1, respectively.

    DOI: 10.1016/j.jcrysgro.2017.01.005

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  13. Direct growth of CdTe on a (211) Si substrate with vapor phase epitaxy using a metallic Cd source Reviewed

    Kenji Iso, Yuya Gokudan, Masumi Shiraishi, Hisashi Murakami, and Akinori Koukitu

    Journal of Electronic Materials   Vol. 46   page: 5884   2017

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  14. Tri-halide vapor-phase epitaxy of GaN using GaCl3 on polar, semipolar, and nonpolar substrates Reviewed

    Iso Kenji, Takekawa Nao, Matsuda Karen, Hikida Kazuhiro, Hayashida Naoto, Murakami Hisashi, Koukitu Akinori

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 10 ) page: 105501   2016.10

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Applied Physics Express  

    Homoepitaxial tri-halide vapor-phase epitaxy (THVPE) growth on polar, semipolar, and nonpolar bulk GaN substrates was demonstrated using GaCl3 as the precursor. The influence of the surface orientation of the substrate on GaN growth by THVPE was compared with that observed for GaN grown by hydride vapor-phase epitaxy. The dependence of the GaN growth on the surface orientation of the substrate was confirmed; GaN could be grown on (1010), (3031), (2021), (1011), and (0001) but not on (0001), (1011), (2021), or (3031). This behavior was explained to be due to the changes in adsorption energy, the magnitudes of which were estimated by theoretical calculations.

    DOI: 10.7567/APEX.9.105501

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  15. Growth of InGaN/GaN light emitting diodes by MOCVD with a thin tapered reactor cell Reviewed

    Iso Kenji, Takaki Ryohei, Ishihama Yoshiyasu, Inagawa Tomokazu, Takahashi Yuzuru

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   Vol. 207 ( 6 ) page: 1386 - 1388   2010.6

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Physica Status Solidi (A) Applications and Materials Science  

    InGaN/GaN-based light emitting diodes (LEDs) can be grown by using metal organic chemical vapor deposition (MOCVD) to make eight, 3-inch diameter wafers with a thin, tapered reactor cell at atmospheric pressure. The reactor configuration was optimized for the purpose of improving the GaN growth rate and its in-plane distribution. The growth rate and the layer uniformity of GaN were improved when the reactor cell was narrowed down and tapered. The on-wafer deviation of the electroluminescence (EL) peak wavelength and power were 5 nm and within 4%, respectively, except at the edge. The full width at half maximum (FWHM) of EL spectrum for an LED grown at atmospheric pressure was consistently smaller than that of one grown at reduced pressure over the entire wavelength range. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssa.200983434

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  16. Customized Filter Cube in Fluorescence Microscope Measurements of InGaN/GaN Quantum-Well Characterization Reviewed

    Masui Hisashi, Sonoda Junichi, Chakraborty Arpan, Yamada Hisashi, Iso Kenji, Pfaff Nathan, Koslow Ingrid, Nakamura Shuji, DenBaars Steven P.

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 48 ( 9 ) page: 0980031 - 0980032   2009.9

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    Language:Japanese   Publisher:Japanese Journal of Applied Physics  

    Modified optical filter elements were fabricated to access blue and violet spectral ranges of InGaN/GaN light-emitting diodes (LEDs) in characterizing luminescence via a fluorescence microscope. As band gap energies of GaN and InGaN layers were close, it was not trivial to separate excitation and luminescence light, which caused slight detection of excitation light. Nevertheless, the results obtained on c- and m-plane LEDs were compared with our previous work, leading consistent understanding of luminescence characteristics in terms of the quantum-confined Stark effect. © 2009 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.48.098003

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  17. Effects of piezoelectric fields on optoelectronic properties of InGaN/GaN quantum-well light-emitting diodes prepared on nonpolar (1 0 (1)over-bar 0) and semipolar (1 1 (2)over-bar 2) orientations Reviewed

    Masui Hisashi, Asamizu Hirokuni, Melo Thiago, Yamada Hisashi, Iso Kenji, Cruz Samantha C., Nakamura Shuji, DenBaars Steven P.

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   Vol. 42 ( 13 ) page: 135106   2009.7

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    Language:Japanese   Publisher:Journal of Physics D: Applied Physics  

    Optical and electrical characteristics of InGaN/GaN quantum-well (QW) light-emitting diodes (LEDs) are the subjects of this study. Samples were prepared on nonpolar (1 0 0) and semipolar (1 1 2) orientations of bulk GaN substrates. Electrical-bias-applied photoluminescence was employed as a characterization technique. It was confirmed that saturation of reverse photocurrent occurred around 0 V in nonpolar LEDs and at positive voltages in (1 1 2)-oriented LEDs, while our previous study found negative voltages in (0 0 0 1)-oriented LEDs (Masui et al 2008 J. Phys. D: Appl. Phys. 41 165105). These results indicated that (1 1 2)-oriented InGaN/GaN QWs experience piezoelectric fields being in the same direction as the built-in field. Piezoelectric field intensity was estimated to be -0.3 MV cm-1 in the (1 1 2)-oriented QW structure. Spectral comparison between photoluminescence and electroluminescence of the LED samples exhibited a tendency that spectral differences were insignificant in single-QW LEDs. © 2009 IOP Publishing Ltd.

    DOI: 10.1088/0022-3727/42/13/135106

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  18. Evaluation of GaN substrates grown in supercritical basic ammonia Reviewed

    Saito Makoto, Yamada Hisashi, Iso Kenji, Sato Hitoshi, Hirasawa Hirohiko, Kamber Derrick S., Hashimoto Tadao, DenBaars Steven P., Speck James S., Nakamura Shuji

    APPLIED PHYSICS LETTERS   Vol. 94 ( 5 ) page: 052109   2009.2

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    Language:Japanese   Publisher:Applied Physics Letters  

    GaN crystals grown by the basic ammonothermal method were investigated for their use as substrates for device regrowth. X-ray diffraction analysis indicated that the substrates contained multiple grains while secondary ion mass spectroscopy (SIMS) revealed a high concentration of hydrogen, oxygen, and sodium. Despite these drawbacks, the emission from the light emitting diode structures grown by metal organic chemical vapor deposition on both the c -plane and m -plane epitaxial wafers was demonstrated. The SIMS depth profiles showed that the diffusion of the alkali metal from the substrate into the epitaxial film was small, especially in the m -direction. © 2009 American Institute of Physics.

    DOI: 10.1063/1.3079813

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  19. Recent progress in nonpolar LEDs as polarized light emitters Reviewed

    Masui Hisashi, Schmidt Mathew, Fellows Natalie, Yamada Hisashi, Iso Kenji, Speck James S., Nakamura Shuji, DenBaars Steven P.

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   Vol. 206 ( 2 ) page: 203 - 205   2009.2

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    The present article provides an overview of developments in nonpolar-oriented GaN-based materials as polarized light emitters over the past 15 years. The strong interest in nonpolar materials emerged around 1996, but nonpolar-oriented light-emitting diodes were not demonstrated until 2004. The later technological key achievement was the commercialization of nonpolar-oriented bulk GaN substrates; it is now feasible to discuss the electronic band structure of such highquality nonpolar GaN as well as device applications of polarized light emitters. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

    DOI: 10.1002/pssa.200880407

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  20. Optical polarization characteristics of m-oriented InGaN/GaN light-emitting diodes with various indium compositions in single-quantum-well structure Reviewed

    Masui Hisashi, Yamada Hisashi, Iso Kenji, Nakamura Shuji, DenBaars Steven P.

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   Vol. 41 ( 22 )   2008.11

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    Language:Japanese   Publisher:Journal of Physics D: Applied Physics  

    Spontaneously polarized light emission from m-plane InGaN/GaN light-emitting diodes was studied as a function of In composition in the InGaN single quantum-well layer. Emission wavelength was varied between 394 and 472 nm. A strong correlation was confirmed between optical polarization and In composition; the higher the In composition, the stronger the optical polarization. The photon-energy difference between the emission spectra associated with the two polarizations, ΔM, was evaluated as a function of current. ΔM exhibited a negative monotonic current dependence for the 394 nm emitting sample and the dependence was changed to positive monotonic as the wavelength became longer towards 472 nm. This change was tentatively attributed to the valence band mixing and the crystal momentum conservation that became relevant with the band filling. ΔM and optical polarization exhibited only a moderate correlation; the Fermi-Dirac function has been used to explain the weakened optical polarization under increased current injection. © 2008 IOP Publishing Ltd.

    DOI: 10.1088/0022-3727/41/22/225104

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  21. Effects of off-axis GaN substrates on optical properties of m-plane InGaN/GaN light-emitting diodes Reviewed

    Yamada Hisashi, Iso Kenji, Masui Hisashi, Saito Makoto, Fujito Kenji, DenBaars Steven P., Nakamura Shuji

    JOURNAL OF CRYSTAL GROWTH   Vol. 310 ( 23 ) page: 4968 - 4971   2008.11

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    Language:Japanese   Publisher:Journal of Crystal Growth  

    Effects of off-axis substrates on m-plane InGaN/GaN light-emitting diodes (LEDs) grown by metal organic chemical vapor deposition were investigated. The surface morphology of n-GaN was improved by increasing an off-axis angle from the m-plane toward the c-plane. The InGaN/GaN quantum wells (QWs) grown on the off-axis substrates toward the c--direction (N-polar) emitted at a longer peak wavelength than the on-axis m-plane substrates, indicating that the off-axis substrates have impact on enhancement of the indium incorporation in the InGaN/GaN QWs. The LED on the c--5° off-axis substrate emitted at 457 nm under DC current of 20 mA and showed 0.7 nm red-shift from 1 to 20 mA. The c--5° off LED showed an optical polarization ratio of 0.91, which is comparable to the nonpolar material. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2008.06.079

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  22. Optical polarization of m-plane In-GaN/GaN light-emitting diodes characterized via confocal microscope Reviewed

    Masui Hisashi, Yamada Hisashi, Iso Kenji, Hirasawa Hirohiko, Fellows Natalie N., Speck James S., Nakamura Shuji, DenBaars Steven P.

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   Vol. 205 ( 5 ) page: 1203 - 1206   2008.5

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    Language:Japanese   Publisher:Physica Status Solidi (A) Applications and Materials Science  

    A confocal microscope was applied to characterize near-field optical polarization of light emission from InGaN-based light-emitting diodes prepared on a nonpolar orientation. Detection of stray light was significantly reduced as a result of the confocal technique compared to broad-area measurements. The confocal measurement required no special sample preparation and obtained data was directly interpretable. A polarization ratio of 0.83 was measured on long-wavelenght emitting devices and was sustained over two orders of magnitude of low current range. Energy shifts and separation of emission peaks for the two polarization components were evaluated to discuss the valence-band structure. Energy shifts indicated that the topmost band {norm of matrix}X〉 had a heavier effective mass than the lower band {norm of matrix}Z〉. Splitting energy of InGaN was estimated to be 30 meV. Results were consistent with the past reports, thus it was confirmed that the confocal microscope is a valid technique to characterize near-field optical polarization. An m-plane InGaN/GaN LED used in the study. ©2008 WILEY-VCH Verlag GmbH & Co. KGaA.

    DOI: 10.1002/pssa.200824044

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  23. Non-polar-oriented InGaN light-emitting diodes for liquid-crystal-display backlighting Reviewed

    Masui Hisashi, Yamada Hisashi, Iso Kenji, Speck James S., Nakamura Shuji, DenBaars Steven P.

    JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY   Vol. 16 ( 4 ) page: 571 - 578   2008.4

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  24. Compositional dependence of nonpolar m-plane InxGa1-xN/GaN light emitting diodes Reviewed

    Yamada Hisashi, Iso Kenji, Saito Makoto, Masui Hisashi, Fujito Kenji, DenBaars Steven P., Nakamura Shuji

    APPLIED PHYSICS EXPRESS   Vol. 1 ( 4 ) page: 0411011 - 0411013   2008.4

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    Language:Japanese   Publisher:Applied Physics Express  

    Characteristics of m-plane InGaN/GaN light emitting diodes (LEDs) with various indium compositions were investigated. X-ray diffraction revealed that indium compositions in the InGaN multi quantum wells (MQWs) on m-plane substrate were 2-3 times lower than those on c-plane substrate. The optical polarization ratio for m-plane LEDs increased from 0.27 to 0.89 with increasing emission wavelength from 383 to 476 nm due to compressively strained InGaN QWs. The output power of electroluminescence decreased above 400 nm although polarization-related internal electric fields were eliminated. © 2008 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.1.041101

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  25. Optical polarization characteristics of InGaN/GaN light-emitting diodes fabricated on GaN substrates oriented between (10(1)over-bar0) and (10(1)over-bar(1)over-bar) planes Reviewed

    Masui Hisashi, Yamada Hisashi, Iso Kenji, Nakamura Shuji, DenBaars Steven P.

    APPLIED PHYSICS LETTERS   Vol. 92 ( 9 ) page: 091105   2008.3

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    Optical polarization characteristics of InGaNGaN light-emitting diodes (LEDs) were studied. Light-emitting diode samples were fabricated on four types of GaN substrates near (10 1- 0) orientation with intentional off-axis cuts of 0°, 5°, 10°, and 27° towards [000 1-]. A confocal microscope was used to characterize the optical polarization of electroluminescence at various currents. The highest polarization ratio of 0.91 was measured on samples fabricated on a 5° off-cut substrate. First moments were calculated on emission spectra to assess emission peak shifts of two polarization components. We drew a conclusion that substrate off-axis cut is a technique to improve optical polarization characteristics of nonpolar-oriented InGaNGaN LEDs. © 2008 American Institute of Physics.

    DOI: 10.1063/1.2890050

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  26. Comparison of InGaN/GaN light emitting diodes grown on m-plane and a-plane bulk GaN substrates Reviewed

    Yamada Hisashi, Iso Kenji, Saito Makoto, Hirasawa Hirohiko, Fellows Natalie, Masui Hisashi, Fujito Kenji, Speck James S., DenBaars Steven P., Nakamura Shuji

    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS   Vol. 2 ( 2 ) page: 89 - 91   2008.3

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    DOI: 10.1002/pssr.200701313

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  27. Impact of substrate miscut on the characteristic of m-plane InGaN/GaN light emitting diodes Reviewed

    Yamada Hisashi, Iso Kenji, Saito Makoto, Fujito Kenji, Denbaars Steven P., Speck James S., Nakamura Shuji

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   Vol. 46 ( 45-49 ) page: L1117 - L1119   2007.12

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    Language:Japanese   Publisher:Japanese Journal of Applied Physics, Part 2: Letters  

    Effect of m-plane GaN substrate miscut was investigated for InGaN/GaN multi quantum wells (MQWs) light emitting diodes (LEDs). The n-GaN and InGaN/GaN LEDs were grown by metal organic chemical vapor deposition on m-plane (1100)GaN substrates with miscut angles toward the [0001̄] direction of 0.01 (nominally on-axis m-plane), 0.45, 0.75, 5.4, and 9.6°. The surface morphology improved with increasing the miscut angles toward the [0001̄] direction. The peak emission wavelength of the electroluminescence grown on the on-axis m-plane and the miscut angle of 0.45° was 391-396 nm, while the miscut angle of 5.4 and 9.6° showed 440-454nm. These results demonstrate that the surface morphology of GaN and In incorporation in the MQWs are strongly impacted by the miscut angle of GaN substrate. © 2007 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.46.L1117

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  28. High brightness blue InGaN/GaN light emitting diode on nonpolar m-plane bulk GaN substrate Reviewed

    Iso Kenji, Yamada Hisashi, Hirasawa Hirohiko, Fellows Natalie, Saito Makoto, Fujito Kenji, Denbaars Steven P., Speck James S., Nakamura Shuji

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   Vol. 46 ( 36-40 ) page: L960 - L962   2007.10

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publisher:Japanese Journal of Applied Physics, Part 2: Letters  

    Improved nonpolar m-plane (11̄00) light emitting diode (LED) with a thick InGaN active layer of 8 nm and a thick GaN barrier layer of 37.5 nm for multi-quantum-well (MQW) structure have been fabricated on low extended defect bulk m-plane GaN substrates using metal organic chemical vapor deposition (MOCVD). The peak wavelength of the electroluminescence (EL) emission from the packaged LED was 468 nm. The output power and external quantum efficiency (EQE) were 8.9 mW and 16.8%, respectively, at a DC driving current of 20 mA. © 2007 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.46.L960

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  29. Continuous-wave operation of AlGaN-cladding-free nonpolar m-plane InGaN/GaN laser diodes Reviewed

    Farrell Robert M., Feezell Daniel F., Schmidt Mathew C., Haeger Daniel A., Kelchner Kathryn M., Iso Kenji, Yamada Hisashi, Saito Makoto, Fujito Kenji, Cohen Daniel A., Speck James S., DenBaars Steven P., Nakamura Shuji

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   Vol. 46 ( 29-32 ) page: L761 - L763   2007.8

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    Language:Japanese   Publisher:Japanese Journal of Applied Physics, Part 2: Letters  

    We demonstrate continuous-wave (CW) operation of nonpolar m-plane InGaN/GaN laser diodes without Al-containing waveguide cladding layers. Thick InGaN quantum wells (QWs) are used to generate effective transverse optical mode confinement, eliminating the need for Al-containing waveguide cladding layers. Peak output powers of more than 25 mW are demonstrated with threshold current densities and voltages of 6.8 kA/cm2 and 5.6 V, respectively. The unpackaged and uncoated laser diodes operated under CW conditions for more than 1.5 h. © 2007 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.46.L761

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  30. Simultaneous control of electrostatic micellar partition and electroosmotic flow-rate by anion-dominated partition into zwitterionic micelles Reviewed

    Iso K, Okada T

    JOURNAL OF CHROMATOGRAPHY A   Vol. 920 ( 1-2 ) page: 317 - 323   2001.6

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  31. Ionic partition to zwitterionic micelles Reviewed

    Iso K., Okada T.

    Studies in Surface Science and Catalysis   Vol. 132   page: 117 - 120   2001

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    Authorship:Lead author   Language:Japanese   Publisher:Studies in Surface Science and Catalysis  

    Capillary electrophoresis has been used to measure the ζ-potential of zwitterionic micelles in various electrolytes. Even for intrinsically neutral zwitterionic micelles, detectable ζ-potential is induced by the imbalance between anionic and cationic partition. Its magnitude and sign are determined by the natures of ions (dominantly anionic ones) and the polarity of surfactant molecules. However, the former is a principal factor governing the ζ-potential of zwitterionic micelles in aqueous solutions.

    DOI: 10.1016/s0167-2991(01)82048-6

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  32. Evaluation of electrostatic potential induced by anion-dominated partition into zwitterionic micelles and origin of selectivity in anion uptake Reviewed

    Iso K, Okada T

    LANGMUIR   Vol. 16 ( 24 ) page: 9199 - 9204   2000.11

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    Authorship:Lead author   Language:Japanese   Publisher:Langmuir  

    The surface potentials of n-dodecyltrimethylammoniopropanesulfonic acid (DDAPS) micelles in various electrolytes have been evaluated by capillary electrophoresis.This zwitterionic micelle has an inner cationic surface and an outer anionic surface and accommodates anions better than cations, indicating that a negative surface potential is induced by anion-dominated partition. Selectivity terms, i.e., solvation changes of ions and ion association between ions and charged groups in the DDAPS micelles, are introduced into the Poisson-Boltzmann equation for the spherical geometry. This model allows the interpretation of differences in the ionic partition and surface potential between electrolytes. The selectivity parameters have been determined by assuming agreement between the zeta potential determined by capillary electrophoresis and the calculated outer surface potential of the micelle. The obtained selectivity parameters can also explain the potentiometrically evaluated partition of ClO4- and I-. It has been confirmed that capillary electrophoresis has wide applicability in surface potential measurements and can detect surface potentials of less than 1 mV. The selectivity origin in the partition into the DDAPS micelles is also discussed on the basis of evaluated parameters. The hydration changes mainly govern the uptake of well-hydrated anions, whereas poorly hydrated anions are partitioned into the micelle principally by ion-pair formation with the cationic groups in the micelles.

    DOI: 10.1021/la0003544

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