研究者詳細 - 堀田　昌宏

論文 - 堀田　昌宏

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Highly effective activation of Mg-implanted p-type GaN by ultra-high-pressure annealing 査読有り

Sakurai, H; Omori, M; Yamada, S; Furukawa, Y; Suzuki, H; Narita, T; Kataoka, K; Horita, M; Bockowski, M; Suda, J; Kachi, T

APPLIED PHYSICS LETTERS 115 巻 ( 14 ) 2019年9月

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

A high activation ratio of acceptors to Mg ions implanted into a homoepitaxial GaN layer was achieved through an ultra-high-pressure annealing (UHPA) process. Capless annealing under a nitrogen pressure of 1 GPa in a temperature range of 1573-1753 K activated acceptors without thermally decomposing the GaN layer. Conventional rapid thermal annealing leads to a serious decomposition at 1573 K, even with an AlN protective cap. The sample annealed at 1673 K under UHPA exhibited very intense cathodoluminescence in near-band edge and donor-acceptor-pair band emissions. The intensities were over one order of magnitude higher than those of the sample treated by conventional annealing. A Hall-effect measurement was obtained in the temperature range of 275-500 K for the UHPA sample. The obtained hole concentration and mobility at 300 K were 3.6 × 1016 cm-3 and 24.1 cm2 V-1 s-1, respectively. The mobility value was close to that of an epitaxial p-type GaN with the same doping concentration. An Arrhenius plot of hole concentrations showed that the acceptor concentration and ionization energy were separately estimated to be (2.6 ± 0.8) × 1018 cm-3 and 212 ± 5 meV, respectively. By comparing the Mg concentrations obtained from secondary ion mass spectrometry, the acceptor activation ratio (acceptor concentration/Mg concentration) of the UHPA samples exceeded 70%. These results suggest that the UHPA process as a postimplantation annealing technique is promising for the fabrication of GaN-based power devices with selective area doping.

DOI： 10.1063/1.5116866

Measurement of avalanche multiplication utilizing Franz-Keldysh effect in GaN p-n junction diodes with double-side-depleted shallow bevel termination 査読有り

Maeda, T; Narita, T; Ueda, H; Kanechika, M; Uesugi, T; Kachi, T; Kimoto, T; Horita, M; Suda, J

APPLIED PHYSICS LETTERS 115 巻 ( 14 ) 2019年9月

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

Avalanche multiplication characteristics of GaN p-n junction diodes (PNDs) with double-side-depleted shallow bevel termination, which exhibit nearly ideal avalanche breakdown, were investigated by photomultiplication measurements using sub-bandgap light. In GaN PNDs under reverse bias conditions, optical absorption induced by the Franz-Keldysh (FK) effect is observed, resulting in a predictable photocurrent. The avalanche multiplication factors were extracted as a ratio of the measured values to the calculated FK-induced photocurrent. In addition, the temperature dependences of the avalanche multiplications were also investigated.

DOI： 10.1063/1.5114844

Franz-Keldysh effect in 4H-SiC p-n junction diodes under high electric field along the ⟨11(2)over-bar0⟩ direction 査読有り

Maeda, T; Chi, XL; Tanaka, H; Horita, M; Suda, J; Kimoto, T

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 9 ) 2019年9月

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

Electric-field dependence of optical absorption induced by Franz-Keldysh (FK) effect strongly depends on the value of the reduced effective mass along electric field. In this study, reverse current-voltage characteristics of 4H-SiC{1120} p-n junction diodes under sub-bandgap illumination were investigated. Under a reverse bias condition, a photocurrent induced by FK effect was observed and increased with the reverse voltage. We calculated a photocurrent with consideration of phonon-assisted optical absorption induced by FK effect in a depletion region using the reduced effective mass perpendicular to the c-axis (μ⊥ = 0.26 m0), and the calculated values showed good agreement with the experimental values. This result indicates that the anisotropy of optical absorption induced by FK effect in 4H-SiC is small, since the reduced effective mass perpendicular to the c-axis (μ⊥ = 0.26 m0) is close to that parallel to the c-axis (μ∥ m = 0.28 m0).

DOI： 10.7567/1347-4065/ab3873

Deep-level transient spectroscopy studies of electron and hole traps in n-type GaN homoepitaxial layers grown by quartz-free hydride-vapor-phase epitaxy 査読有り

Kanegae, K; Fujikura, H; Otoki, Y; Konno, T; Yoshida, T; Horita, M; Kimoto, T; Suda, J

APPLIED PHYSICS LETTERS 115 巻 ( 1 ) 2019年7月

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

We studied deep levels in quartz-free hydride-vapor-phase epitaxy (QF-HVPE)-grown homoepitaxial n-type GaN layers within which three electron and eight hole traps were detected. The dominant electron and hole traps observed in the QF-HVPE-grown GaN layers were E3 (EC - 0.60 eV) and H1 (EV + 0.87 eV), respectively. We found that the E3 trap density of QF-HVPE-grown GaN (∼1014 cm-3) was comparable with that of MOVPE-grown GaN layers, whereas the H1 trap density of QF-HVPE-grown GaN (∼1014 cm-3) was much smaller than that of an MOVPE-grown GaN layer with a low-residual-carbon growth condition. A detailed analysis of the QF-HVPE-grown GaN layers revealed that the H1 trap density is almost equal to the carbon impurity concentration and other impurities that compensate the Si donors besides the carbon impurity were hardly detected in the QF-HVPE-grown GaN layers.

DOI： 10.1063/1.5098965

Shockley-Read-Hall lifetime in homoepitaxial p-GaN extracted from recombination current in GaN p-n<SUP>+</SUP> junction diodes 査読有り Open Access

Maeda, T; Narita, T; Ueda, H; Kanechika, M; Uesugi, T; Kachi, T; Kimoto, T; Horita, M; Suda, J

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

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

The Shockley-Read-Hall (SRH) lifetime in homoepitaxial p-GaN (N a = 1 × 1017 cm-3) is investigated by analyzing forward current-voltage (I-V) characteristics in GaN-on-GaN p-n+ junction diodes with mesa-isolation structure. The ideality factor around 2 due to recombination current was obtained in the 1.8-2.7 V window, which is different from the characteristic of a p+-n- junction involving considerable diffusion current. The recombination current was proportional to the junction area, indicating that the recombination current is a bulk component, not a mesa-surface component. Analyzing the recombination current with consideration of the SRH recombination rate in the depletion layer, we obtained an SRH lifetime of 46 ps at 298 K. The temperature dependence of the I-V characteristics was also investigated and the SRH lifetimes were extracted in the range of 223-573 K. The SRH lifetime in homoepitaxial p-GaN followed the empirical power law of = 1.2 × 10-16 × T 2.25 (s).

DOI： 10.7567/1347-4065/ab07ad

Design and Fabrication of GaN p-n Junction Diodes With Negative Beveled-Mesa Termination 査読有り

Maeda, T; Narita, T; Ueda, H; Kanechika, M; Uesugi, T; Kachi, T; Kimoto, T; Horita, M; Suda, J

IEEE ELECTRON DEVICE LETTERS 40 巻 ( 6 ) 頁： 941 - 944 2019年6月

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

We report on homoepitaxial GaN p-n junction diodes with a negative beveled-mesa termination. The electric field distribution in a beveled-mesa was investigated using TCAD simulation, and the devices were designed using currently available GaN growth techniques. Shallow-angle (ca. 10°) negative bevel GaN p-n junction diodes were fabricated with various Mg acceptor concentrations in the p-layers. The suppression of electric field crowding and improvement of the breakdown voltage were observed, as the Mg concentration was decreased. The parallel-plane breakdown field of 2.86 MV/cm was obtained for a device with the breakdown voltage of 425 V.

DOI： 10.1109/LED.2019.2912395

Estimation of Impact Ionization Coefficient in GaN by Photomulitiplication Measurement Utilizing Franz-Keldysh Effect 査読有り

Maeda, T; Narita, T; Ueda, H; Kanechika, M; Uesugi, T; Kachi, T; Kimoto, T; Horita, M; Suda, J

2019 31ST INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES AND ICS (ISPSD) 2019-May 巻頁： 59 - 62 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of the International Symposium on Power Semiconductor Devices and ICs

A valanche multiplication characteristics in GaN p-n junction diodes (PNDs) under high reverse bias conditions were investigated. The GaN-on-GaN PNDs with double-side-depleted shallow bevel termination, which showed low reverse leakage current and excellent avalanche capability, were used for the measurements. Under sub-bandgap light illumination, the photocurrents induced by Franz-Keldysh (FK) effect, which can be well reproduced by the theoretical calculations of the optical absorption, and their avalanche multiplications were observed. The multiplication factors were extracted as the ratios of the experimental photocurrents to the calculated FK-induced photocurrent. Under an assumption of equal impact ionization coefficients of electrons and holes, the electric-field dependence of an impact ionization coefficient in GaN were estimated.

DOI： 10.1109/ispsd.2019.8757676

Acceptors activation of Mg-ion implanted GaN by ultra-high-pressure annealing 査読有り

Sakurai, H; Omori, M; Yamada, S; Koura, A; Suzuki, H; Narita, T; Kataoka, K; Horita, M; Kowski, MB; Suda, J; Kachi, T

2019 NINETEENTH INTERNATIONAL WORKSHOP ON JUNCTION TECHNOLOGY (IWJT) 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：19th International Workshop on Junction Technology, IWJT 2019

For the solution to global energy issues, highly-efficient energy conversion using next-generation power devices is required. Gallium nitride (GaN) having superior properties such as high breakdown electric field (2.8-3.75 MV/cm) is a powerful candidate for next-generation high-power semiconductor devices. [1] , [2] The selective area doping makes it possible to precisely engineer high-power devices with complex structures, allowing formation of low-resistivity region for contacting electrodes and optimization of the electric field configuration in the edge termination represented by the field limiting ring (FLR) and in the junction barrier Schottky (JBS) structures, as used in Si and SiC power devices.

DOI： 10.23919/iwjt.2019.8802621

Impact Ionization Coefficients in GaN Measured by Above- and Sub-<i>E</i><sub>g</sub> Illuminations for p<SUP>-</SUP>/n<SUP>+</SUP> Junction

Maeda, T; Narita, T; Yamada, S; Kachi, T; Kimoto, T; Horita, M; Suda, J

2019 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM) 2019年

The origin of carbon-related carrier compensation in p-type GaN layers grown by MOVPE

Narita, T; Tomita, K; Tokuda, Y; Kogiso, T; Horita, M; Kachi, T

JOURNAL OF APPLIED PHYSICS 124 巻 ( 21 ) 2018年12月

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 Applied Physics

The role of carbon impurities in p-type GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) was investigated. The lightly Mg-doped (∼1017 cm-3) p-type GaN samples with different carbon concentration [C] were prepared by controlling growth temperature and pressure. Temperature-dependent Hall-effect analyses exhibited an increase in donor concentration with increasing [C]. The low-temperature mobility also decreased with increasing [C], as a result of mobility limitation due to ionized impurity scattering. These results show that carbon atoms in MOVPE-grown p-GaN layers act as ionized donors and cause carrier compensation. Deep-level transient spectroscopy (DLTS) using bias pulses detected the existence of Hd traps (EV +0.88 eV) arising from the 0/-1 charge state of carbon on nitrogen sites (CN). The concentrations of Hd traps closely corresponded to [C] values in p-type GaN layers. Employing low-frequency capacitance DLTS to avoid carrier freeze-out at low temperatures, we newly discovered the Ha trap (EV +0.29 eV) whose concentration was directly proportional to the [C] value. These findings suggest that the Ha trap originates from CN identical to the Hd trap. Based on prior theoretical calculations of energy levels, the Ha trap can reasonably be assigned to a +1/0 donor state of CN. These results strongly suggest that a CN having two different charged states can compensate an electron and a hole in n-type and p-type GaN layers, respectively.

DOI： 10.1063/1.5057373

Phonon-assisted optical absorption due to Franz-Keldysh effect in 4H-SiC p-n junction diode under high reverse bias voltage

Maeda, T; Chi, XL; Horita, M; Suda, J; Kimoto, T

APPLIED PHYSICS EXPRESS 11 巻 ( 9 ) 2018年9月

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

Photocurrent in a 4H-SiC p-n junction diode under illumination with sub-bandgap light was investigated. Under a high reverse bias condition, the photocurrent significantly increased with an increase in the reverse bias voltage. We calculated the photocurrent taking into consideration the phonon-assisted optical absorption due to the Franz-Keldysh effect. The calculated photocurrent showed good agreement with the experimental results. The photocurrent also increased at elevated temperatures, which could be quantitatively explained by the redshift of the 4H-SiC absorption edge (the shrinkage of the bandgap) and the increase in the phonon occupation number with rising temperature.

DOI： 10.7567/APEX.11.091302

Accurate method for estimating hole trap concentration in n-type GaN via minority carrier transient spectroscopy

Kanegae, K; Horita, M; Kimoto, T; Suda, J

APPLIED PHYSICS EXPRESS 11 巻 ( 7 ) 2018年7月

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

We propose an analysis method for the accurate estimation of the hole trap (H1, EV + 0.85 eV) concentration in n-type GaN via minority carrier transient spectroscopy (MCTS). The proposed method considers both the hole occupation during a filling (current injection) period and the quick carrier recombination via the hole traps near the depletion layer edge immediately after a reverse bias is applied. The reverse bias voltage dependence of the MCTS spectrum indicates that an accurate trap concentration, as well as the hole diffusion length and electron capture cross section of the hole trap, can be determined.

DOI： 10.7567/APEX.11.071002

Characterization of carrier concentration and mobility of GaN bulk substrates by Raman scattering and infrared reflectance spectroscopies

Kanegae, K; Kaneko, M; Kimoto, T; Horita, M; Suda, J

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

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

n-Type GaN bulk substrates with carrier concentrations (n) of 1016-1020 cm%3 were characterized by Raman scattering (350-5000 cm-1) and infrared reflectance (400-5000 cm%1) spectroscopies. Experimental spectra were fitted with the curves calculated from the dielectric function and carrier concentration and mobility of the GaN bulk. The obtained values agree well with the values from Hall-effect measurements for n of 1016-1019 cm-3 in Raman scattering measurements and for n of 1018-1020 cm-3 in infrared reflectance measurements.

DOI： 10.7567/JJAP.57.070309

Franz-Keldysh effect in GaN p-n junction diode under high reverse bias voltage

Maeda, T; Narita, T; Kanechika, M; Uesugi, T; Kachi, T; Kimoto, T; Horita, M; Suda, J

APPLIED PHYSICS LETTERS 112 巻 ( 25 ) 2018年6月

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

Photocurrent induced by sub-bandgap light absorption due to the Franz-Keldysh effect was observed in GaN p-n junction diodes under a high reverse bias voltage. The photocurrent increased with the reverse bias voltage and the increase was found to be more significant as the wavelength approached the absorption edge of GaN. The photocurrent was calculated with consideration of light absorption induced by the Franz-Keldysh effect in the depletion layer. The calculated curves showed excellent agreement with the experimental curves. The photocurrent also increased with an increase in temperature and this could be quantitatively explained by the red-shift of the GaN absorption edge with the increase in temperature.

DOI： 10.1063/1.5031215

Sources of carrier compensation in metalorganic vapor phase epitaxy-grown homoepitaxial n-type GaN layers with various doping concentrations

Sawada, N; Narita, T; Kanechika, M; Uesugi, T; Kachi, T; Horita, M; Kimoto, T; Suda, J

APPLIED PHYSICS EXPRESS 11 巻 ( 4 ) 2018年4月

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

The source of carrier compensation in metalorganic vapor phase epitaxy (MOVPE)-grown n-type GaN was quantitatively investigated by Halleffect measurement, deep-level transient spectroscopy, and secondary ion mass spectrometry. These analysis techniques revealed that there were at least three different compensation sources. The carrier compensation for samples with donor concentrations below 5 1016 cm3 can be explained by residual carbon and electron trap E3 (EC % 0.6 eV). For samples with higher donor concentrations, we found a proportional relationship between donor concentration and compensating acceptor concentration, which resulted from a third source of compensation. This is possibly due to the self-compensation effect.

DOI： 10.7567/APEX.11.041001

Parallel-Plane Breakdown Fields of 2.8-3.5 MV/cm in GaN-on-GaN p-n Junction Diodes with Double-Side-Depleted Shallow Bevel Termination 査読有り

Maeda, T; Narita, T; Ueda, H; Kanechika, M; Uesugi, T; Kachi, T; Kimoto, T; Horita, M; Suda, J

2018 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM) 2018年

Characterization of lightly-doped n- and p-type homoepitaxial GaN on free-standing substrates 招待有り査読有り

Horita M., Suda J.

IMFEDK 2017 - 2017 International Meeting for Future of Electron Devices, Kansai 頁： 86 - 87 2017年7月

記述言語：英語出版者・発行元：IMFEDK 2017 - 2017 International Meeting for Future of Electron Devices, Kansai

Hall-effect measurements for n-type and p-type GaN with low doping concentration are presented. The GaN layers were grown by metal-organic vapor phase epitaxy on hydride-vapor-phase-epitaxy-grown free-standing GaN substrates. For n-GaN, the origin of acceptor which compensating donor is not only C but also native defects for the Si doping concentration of 1016 cm-3 level. The electron mobility is mainly limited by ionized impurity scattering or polar optical phonon scattering in the temperature less or higher than 200 K, respectively. For p-GaN, lightly Mg doping of mid 1016 cm-3 was achieved, which shows the donor concentration of 3.2×1016 cm-3 and the mobility of 31 cm2/Vs at 300 K.

DOI： 10.1109/IMFEDK.2017.7998055

Solution-derived SiO2 gate insulator formed by CO2 laser annealing for polycrystalline silicon thin-film transistors 査読有り

Daisuke Hishitani, Masahiro Horita, Yasuaki Ishikawa, Hiroshi Ikenoue, Yukiharu Uraoka

Japanese Journal of Applied Physics 56 巻 ( 5 ) 2017年5月

Temperature dependence of barrier height in Ni/n-GaN Schottky barrier diode 査読有り

Takuya Maeda, Masaya Okada, Masaki Ueno, Yoshiyuki Yamamoto, Tsunenobu Kimoto, Masahiro Horita, Jun Suda

Applied Physics Express 10 巻 ( 5 ) 2017年5月

Hall-effect measurements of metalorganic vapor-phase epitaxy-grown p-type homoepitaxial GaN layers with various Mg concentrations 査読有り

Masahiro Horita, Shinya Takashima, Ryo Tanaka, Hideaki Matsuyama, Katsunori Ueno, Masaharu Edo, Tokio Takahashi, Mitsuaki Shimizu, Jun Suda

Japanese Journal of Applied Physics 56 巻 ( 3 ) 2017年3月

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