研究者詳細 - 冨田　一義

写真a

トミタ　カズヨシ

冨田　一義

TOMITA Kazuyoshi

所属

未来材料・システム研究所豊田中研GaNパワーデバイス産学協同研究部門特任教授

学位 1

博士（工学）（ 2009年3月名古屋大学）

学位の先頭へ▲

論文 35

Rapid Mg substitution to Ga-sites and slow defect recovery revealed by depth-resolved photoluminescence in Mg/N-ion-implanted GaN 査読有り国際誌

Kataoka, K; Narita, T; Tomita, K; Yamada, S; Kachi, T

APPLIED PHYSICS LETTERS 125 巻 ( 19 ) 2024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）出版者・発行元：Applied Physics Letters

Toward p-type GaN formation by Mg ion implantation (I/I) applicable to devices, depth-resolved photoluminescence (PL) revealed key behaviors during activation annealing for precise profile control, such as Mg substitution into Ga-sites (MgGa) and recovery of I/I defects. Depth profiles of the MgGa acceptor concentration were measured for Mg-I/I and Mg/N-I/I samples after ultra-high-pressure annealing at 1300 °C for 1-60 min. The cycle of low-damage dry etching and PL measurement was repeated over the I/I depth, and the MgGa concentration was estimated at each depth based on the calibration curve for the PL intensity ratio between acceptor-bound excitons (A0XA) and free excitons (FXA). In the region deeper than the I/I peak of 0.3 μm, almost all of the Mg atoms rapidly substituted into Ga-sites during the short annealing process. By contrast, the Mg substitution ratios in the shallower region were low when the annealing process was short but were improved by the sequential N-I/I. The low substitution ratio can be explained by MgGa bonding with nitrogen vacancy (VN)-related defects, while the implanted N-ions can compensate them. The PL intensity near the mean implantation depth of Mg/N-I/I was gradually improved as the annealing duration was increased to 60 min, indicating a slow reduction of nonradiative recombination centers. Simultaneously, the green luminescence associated with the VN-related defects decreased in intensity with increasing annealing time. Therefore, the main effect of prolonging annealing is the enhancement of slow defect recovery rather than enhancement of the Mg substitution as a fast process.

DOI： 10.1063/5.0232083

Web of Science

Scopus
A High Channel Mobility and a Normally-off Operation of a Vertical GaN Metal-Oxide-Semiconductor Field-Effect Transistors using an AlSiO/AlN Gate Stack Structure on m-plane Trench Sidewall 査読有り国際共著国際誌

Kanechika, M; Ito, K; Narita, T; Tomita, K; Iwasaki, S; Kikuta, D; Kachi, T

PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS 18 巻 ( 11 ) 2024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）出版者・発行元：Physica Status Solidi - Rapid Research Letters

An AlSiO/AlN-interlayer gate stack formed on c-plane GaN metal-oxide-semiconductor (MOS) devices was previously developed to enhance the interface of the gate insulator. By utilizing this gate stack structure, a channel mobility of over 200 cm2 Vs−1 on c-plane was obtained. However, the threshold voltage was negative because of the polarization charge at the AlN/GaN interface. This study extends the application of this gate stack structure to the nonpolar m-plane, which is obtained from a trench sidewall. Both a high channel mobility of 150 cm2 Vs−1 and a threshold voltage of 1.3 V is successfully achieved, normally-off operation. This achievement holds significant promise for the gate structure of a GaN trench-gate MOS field-effect transistor (MOSFET). The limiting factor of the channel mobility is Coulomb scattering in a low electric field, whereas surface roughness scattering is dominant in a higher field.

DOI： 10.1002/pssr.202400010

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Scopus
Depth Analyses of Mg-Acceptor and Si-Donor Concentrations in GaN by Combining Stepwise Etching and Photoluminescence 査読有り国際誌

Kataoka, K; Narita, T; Tomita, K; Yamada, S; Kachi, T

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 261 巻 ( 11 ) 2024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）出版者・発行元：Physica Status Solidi (B) Basic Research

The depth profiles of the Mg-acceptor or Si-donor concentration in GaN are visualized using stepwise etching and photoluminescence (PL) measurements. Low-damage etching techniques are applied: multistep-bias inductively coupled plasma reactive ion etching for p-type GaN and electrochemical etching for n-type GaN. To determine the concentration calibration curve, the PL intensity ratios of Mg-neutral acceptor or Si-neutral donor-bound excitons to free excitons are plotted against Mg or Si atomic concentrations in etched GaN epitaxial layers having depth distributions of dopant concentrations, as estimated by secondary ion mass spectrometry. The quantitative accuracy of the calibration curve is ensured by the appropriate sample temperature and excitation density ranges for PL. The stepwise dry etching and the Mg acceptor quantification by PL using this calibration curve are applied to Mg-ion-implanted GaN after ultra-high-pressure annealing at 1300 °C for 1 min. The obtained depth profile of the Mg-acceptor concentration is consistent with the Mg atomic concentration profile in the region deeper than the implantation peak, whereas the acceptor concentration in the shallow region is lower than the Mg atomic concentration. This analysis is useful for revealing the site substitution ratio of dopants in GaN materials partially involving inactive dopants.

DOI： 10.1002/pssb.202300528

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Transport Properties in GaN Metal-Oxide-Semiconductor Field-Effect Transistor Almost Free of Interface Traps with AlSiO/AlN/p-Type GaN Gate Stack 査読有り国際誌

Narita, T; Ito, K; Tomita, K; Iguchi, H; Iwasaki, S; Horita, M; Kano, E; Ikarashi, N; Kikuta, D

PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS 2024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）出版者・発行元：Physica Status Solidi - Rapid Research Letters

The factors limiting channel mobility in AlSiO/p-type GaN metal–oxide–semiconductor (MOS) field-effect transistors are examined by performing Hall-effect measurements in conjunction with a gate bias, with and without a thin AlN interlayer. In the absence of this interlayer, the free carrier concentration associated with the Hall effect is significantly reduced compared with the net gate charge density estimated from capacitance–voltage data, indicating that electrons are trapped to a significant extent at the MOS interface. These interface traps are found to have an energy ≈20 meV above the Fermi level in strong inversion based on temperature-dependent Hall effect data. The insertion of a 0.8 nm-thick AlN interlayer eliminates charge trapping such that almost all gate charges are mobile. The mobility components could be divided into types based on their effect on the effective electric field perpendicular to the channel. Coulomb scattering centers resulting from interface states are evidently reduced by inserting the AlN interlayer, which also enhances the channel mobility to over 150 cm2 V−1s−1.

DOI： 10.1002/pssr.202400141

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Extraction of gap states in AlSiO/AlN/GaN metal-oxide-semiconductor field-effect transistors using the multi-terminal capacitance-voltage method 査読有り国際誌

Narita, T; Ito, K; Iguchi, H; Iwasaki, S; Tomita, K; Kikuta, D

APPLIED PHYSICS LETTERS 124 巻 ( 10 ) 2024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）出版者・発行元：Applied Physics Letters

Direct extraction of gap states from a metal-oxide-semiconductor field-effect transistor (MOSFET) in which inversion electrons and holes in a p-type body coexist is challenging. We demonstrate gap-state extraction in lateral-type GaN MOSFETs with high channel mobilities using multi-terminal capacitance-voltage (C-V) methods. The gate stack of the MOSFET was composed of AlSiO/AlN/p-type GaN formed on a p+/n+ GaN tunnel junction structure. The substrate electrode was short-circuited to a p-type body layer through the tunnel junction. The MOSFET was equipped with gate, source, drain, body, and substrate electrodes. When the gate was the high side and the other electrodes were the low side in the AC circuit, a V-shaped C-V curve was obtained because of electron inversion and hole accumulation. When the body/substrate electrodes were connected to the ground level (i.e., split C-V method), the inversion electrons between the gate and source/drain electrodes could be evaluated. We proposed a “reverse” split C-V method in which the source/drain electrodes are grounded and the body/substrate electrodes are connected to the low side. This method enabled extraction of gap states near the valence-band maximum of GaN, with exclusion of the overlap capacitance and the capacitance due to inversion electrons. The proposed method demonstrated overall gap states in the GaN MOSFET with a wide bandgap. The results suggest that hole traps with discrete energy levels caused negative bias instability (NBI) in the GaN MOSFET. Furthermore, NBI and discrete gap states were consistently suppressed by Mg doping at >1018 cm−3 into a p-type body.

DOI： 10.1063/5.0191066

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Over 200 cm(2) V-1 s(-1) of electron inversion channel mobility for AlSiO/GaN MOSFET with nitrided interface 査読有り国際誌

Ito Kenji, Iwasaki Shiro, Tomita Kazuyoshi, Kano Emi, Ikarashi Nobuyuki, Kataoka Keita, Kikuta Daigo, Narita Tetsuo

APPLIED PHYSICS EXPRESS 16 巻 ( 7 ) 2023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）出版者・発行元：Applied Physics Express

By controlling a metal-oxide-semiconductor interface of an AlSiO/GaN system, the electron inversion channel mobility was significantly improved to 229 cm2 V−1 s−1 in a field-effect transistor. A 3 nm thick AlN interlayer formed by atomic layer deposition effectively suppressed the oxidation of the GaN surface and reduced the border traps, resulting in high channel mobility. An additional nitrogen radical treatment before AlN deposition further improved the subthreshold slope and the channel mobility, which was consistent with the lower charged defects extracted from the mobility analysis in the low effective normal field region.

DOI： 10.35848/1882-0786/ace33c

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Effects of proton irradiation-induced point defects on Shockley-Read-Hall recombination lifetimes in homoepitaxial GaN p-n junctions 査読有り国際誌

Narita Tetsuo, Kanechika Masakazu, Tomita Kazuyoshi, Nagasato Yoshitaka, Kondo Takeshi, Uesugi Tsutomu, Ikeda Satoshi, Kosaki Masayoshi, Oka Tohru, Suda Jun

APPLIED PHYSICS LETTERS 122 巻 ( 11 ) 頁： 113505 2023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）出版者・発行元：Applied Physics Letters

This work examined the intentional generation of recombination centers in GaN p-n junctions on freestanding GaN substrates. Irradiation with a 4.2 MeV proton beam was used to create a uniform distribution of vacancies and interstitials across GaN p+/n- and p-/n+ junctions through anode electrodes. With increasing proton dose, the effective doping concentrations were found to be reduced. Because the reduction in the doping concentration was much higher than the hydrogen atom concentration, this decrease could not be attributed solely to carrier compensation resulting from interstitial hydrogen atoms. In fact, more than half of the electron and hole compensation was caused by the presence of point defects. These defects evidently served as Shockley-Read-Hall (SRH) recombination centers such that the SRH lifetimes were reduced to several picoseconds from several hundred picoseconds prior to irradiation. The compensation for holes in the p-/n+ junctions was almost double that for electrons in the p+/n- junctions. Furthermore, the SRH lifetimes associated with p-/n+ junctions were shorter than those for p+/n- junctions for a given proton dose. These differences can be explained by variations in the charge state and/or the formation energy of intrinsic point defects in the p-type and n-type GaN layers. The results of the present work indicate the asymmetry of defect formation in GaN based on the fact that intrinsic point defects in p-type GaN readily compensate for holes.

DOI： 10.1063/5.0141781

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Reliability issues of gate oxides and p-n junctions for vertical GaN metal-oxide-semiconductor field-effect transistors 招待有り国際誌

Narita Tetsuo, Kikuta Daigo, Ito Kenji, Shoji Tomoyuki, Mori Tomohiko, Yamaguchi Satoshi, Kimoto Yasuji, Tomita Kazuyoshi, Kanechika Masakazu, Kondo Takeshi, Uesugi Tsutomu, Kojima Jun, Suda Jun, Nagasato Yoshitaka, Ikeda Satoshi, Watanabe Hiroki, Kosaki Masayoshi, Oka Tohru

2023 IEEE INTERNATIONAL RELIABILITY PHYSICS SYMPOSIUM, IRPS 2023-March 巻 2023年

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記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE International Reliability Physics Symposium Proceedings

We focus on reliability issues of gate oxides and p-n junctions to realize vertical GaN metal-oxide-semiconductor field-effect transistors (MOSFETs). An annealed AlSiO gate oxide on GaN displayed a lifetime of over 20 years at 150 °C and suppressed positive bias instability in MOSFETs. The key to high channel mobility and stability under positive gate bias is the interface structure designed to minimize oxide border traps. We also evaluated the reliability of GaN p-n diodes (PNDs) on freestanding GaN substrates with different threading dislocation densities. The reverse leakage for PNDs involving threading dislocations was explained by variable-range hopping, while the reverse leakage for dislocation-free PNDs was dominated by band-to-band tunneling. The fabricated PNDs demonstrated excellent robustness under high-temperature reverse bias. However, after continuous forward current stress, reverse leakage pathways were formed at threading screw dislocations, which should be minimized in future GaN substrates.

DOI： 10.1109/IRPS48203.2023.10118047

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Relationship of carbon concentration and slow decays of photoluminescence in homoepitaxial n-type GaN layers 査読有り

Kato Masashi, Maeda Takuto, Ito Kenji, Tomita Kazuyoshi, Narita Tetsuo, Kachi Tetsu

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( 7 ) 2022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）出版者・発行元：Japanese Journal of Applied Physics

In this study, we analyzed the slow decay in time-resolved photoluminescence (TR-PL) of n-type GaN homoepitaxial layers with carbon concentrations of (0.26-4.0) × 1016 cm-3. The relative signal intensities of the slow decays to the TR-PL signals at t = 0 s increased almost linearly with increased carbon concentration, suggesting that the carrier recombination process is subjected to the deep level formed by the carbon atoms in GaN. Slow decay curves were calculated based on the rate equations for trapping and emission at the deep level. The experimental carbon concentration dependence of the time constants and the relative signal intensities was reproduced by calculation. TR-PL is a technique used to estimate carbon concentrations in GaN homoepitaxial layers.

DOI： 10.35848/1347-4065/ac79ec

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Scopus
Identification of type of threading dislocation causing reverse leakage in GaN p-n junctions after continuous forward current stress 査読有り

Narita Tetsuo, Kanechika Masakazu, Kojima Jun, Watanabe Hiroki, Kondo Takeshi, Uesugi Tsutomu, Yamaguchi Satoshi, Kimoto Yasuji, Tomita Kazuyoshi, Nagasato Yoshitaka, Ikeda Satoshi, Kosaki Masayoshi, Oka Tohru, Suda Jun

SCIENTIFIC REPORTS 12 巻 ( 1 ) 頁： 1458 2022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： 10.1038/s41598-022-05416-3

Web of Science

Scopus

PubMed
Analysis of intrinsic reverse leakage current resulting from band-to-band tunneling in dislocation-free GaN p-n junctions 査読有り国際誌

Shoji Tomoyuki, Narita Tetsuo, Nagasato Yoshitaka, Kanechika Masakazu, Kondo Takeshi, Uesugi Tsutomu, Tomita Kazuyoshi, Ikeda Satoshi, Mori Tomohiko, Yamaguchi Satoshi, Kimoto Yasuji, Kojima Jun, Suda Jun

APPLIED PHYSICS EXPRESS 14 巻 ( 11 ) 2021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）出版者・発行元：APPLIED PHYSICS EXPRESS

DOI： 10.35848/1882-0786/ac2a03

Web of Science
Photoionization cross section ratio of nitrogen-site carbon in GaN under sub-bandgap-light irradiation determined by isothermal capacitance transient spectroscopy 査読有り国際誌

Kanegae Kazutaka, Narita Tetsuo, Tomita Kazuyoshi, Kachi Tetsu, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

APPLIED PHYSICS EXPRESS 14 巻 ( 9 ) 2021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）出版者・発行元：Applied Physics Express

The ratio of the photoionization cross sections (σo/n σ o/p) of carbon substituting at the nitrogen site [CN (0/-)] in n-type GaN, which is detected as a hole trap H1 (EV + 0.85 eV) under sub-bandgap-light irradiation (390 nm), is determined with isothermal capacitance transient spectroscopy (ICTS). The current-injection ICTS and the sub-bandgap-light-excited ICTS were compared for the same p+-n junction diode, whereby the hole occupancy ratio (fT) was obtained. Analysis of the dependence of fT on the temperature gave σo/n σ o/p of 3.0 was then used to estimate the charge state of CN (0/-) under sub-bandgap-light irradiation.

DOI： 10.35848/1882-0786/ac16ba

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Increase of reverse leakage current at homoepitaxial GaN p-n junctions induced by continuous forward current stress 査読有り国際誌

Narita Tetsuo, Nagasato Yoshitaka, Kanechika Masakazu, Kondo Takeshi, Uesugi Tsutomu, Tomita Kazuyoshi, Ikeda Satoshi, Yamaguchi Satoshi, Kimoto Yasuji, Kosaki Masayoshi, Oka Tohru, Kojima Jun, Suda Jun

APPLIED PHYSICS LETTERS 118 巻 ( 25 ) 2021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）出版者・発行元：Applied Physics Letters

Reliability tests involving the application of high electrical stresses were employed to assess GaN-based vertical p-n junctions fabricated on freestanding GaN substrates with threading dislocation densities less than 104 cm−2. Electric field crowding at the device edges was eliminated by employing a shallow bevel mesa structure, thus allowing an evaluation of the reliability of the internal p-n junctions. The p-n diodes exhibited reproducible avalanche breakdown characteristics over the temperature range of 25-175 °C. No degradation was observed even during tests in which the devices were held under a reverse bias near the breakdown voltage. Despite this high degree of reliability in response to reverse bias stress, a small number of diodes were degraded during continuous forward current tests, although the majority of diodes remained unchanged. The reverse leakage current exhibited by degraded diodes was increased with an increase in the forward current density within the range of 50-500 A/cm2, while the breakdown voltages were unchanged in response to current stress. The leakage level increased exponentially with an increase in the total amount of injected carriers but eventually plateaued. In the degraded p-n diode, a luminous point in an emission microscope corresponded to one of the threading dislocations observed in the synchrotron x-ray topography, indicating that a specific dislocation played as a leakage path after injecting carriers.

DOI： 10.1063/5.0053139

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Contribution of the carbon-originated hole trap to slow decays of photoluminescence and photoconductivity in homoepitaxial n-type GaN layers 査読有り国際誌

Kato Masashi, Asada Takato, Maeda Takuto, Ito Kenji, Tomita Kazuyoshi, Narita Tetsuo, Kachi Tetsu

JOURNAL OF APPLIED PHYSICS 129 巻 ( 11 ) 2021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）出版者・発行元：Journal of Applied Physics

N-type GaN epitaxial layers grown via metal organic vapor-phase epitaxy typically exhibit a yellow luminescence (YL) band owing to carbon-related deep levels in the photoluminescence spectra. The decay of YL after pulse excitation involves a long time constant (∼0.2 ms at room temperature), whereas microwave photoconductivity decay (μ-PCD) curves show the corresponding component of the time constant. To clarify the origin of the long decay time, the temperature-dependent time constants of YL decay and μ-PCD curves are analyzed using a numerical model based on rate equations for trapping and emission through a deep level. The characteristics of the decays are well reproduced by a recombination model using a hole trap H1 at an energy of EV + 0.88 eV because of the acceptor-like state of carbon on a nitrogen site (CN) whose electron capture cross section (σn) is estimated to be 3 × 10-21 cm2. The slow decay in μ-PCD signals indicates that the electrons before being captured to H1 traps are free electrons in the conduction band. These findings indicate that the slow recombination process through CN results in tail currents in the turn-off switching periods of devices.

DOI： 10.1063/5.0041287

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Analysis of channel mobility in GaN-based metal-oxide-semiconductor field-effect transistors 査読有り国際誌

Ito Kenji, Tomita Kazuyoshi, Kikuta Daigo, Horita Masahiro, Narita Tetsuo

JOURNAL OF APPLIED PHYSICS 129 巻 ( 8 ) 2021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）出版者・発行元：Journal of Applied Physics

The factors limiting channel mobility in AlSiO/p-type GaN-based metal-oxide-semiconductor field-effect transistors (MOSFETs) were systematically investigated. MOSFETs with various thin interfacial layers (ILs) between Al0.78Si0.22Oy films and Mg-doped GaN layers were prepared and found to exhibit different channel mobilities. The maximum effective mobility showed a significant correlation with the threshold voltage (Vt) and the hysteresis (ΔVt) in the transfer characteristics of these devices, such that the mobility decreased with increasing Vt and ΔVt. This effect can be explained by electron capture in and emission from border traps situated near the conduction band minimum for GaN. The insertion of a 3-nm-thick SiO2 IL drastically enhanced the effective mobility and simultaneously reduced the ΔVt value. Hall effect measurements with an applied gate voltage were used to determine the mobility of free electrons while excluding electrons captured in the border traps. The Hall effect mobility was much higher than the effective mobility, indicating that mobility was in fact reduced by the capture of electrons by the border traps. The ratio of electrons captured by border traps to the overall electrons induced by a gate bias was greatly lowered in a MOSFET incorporating a SiO2 IL. When a high vertical electric field of approximately 1 MV/cm was present in the device channel, the Hall effect mobility was slightly increased following the insertion of an IL. These results suggest that the IL reduced the interfacial roughness and/or affected the screening out of scattering due to potential fluctuations of the AlSiO.

DOI： 10.1063/5.0040700

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水素イオン注入n+pGaNのo.88 eV正孔トラップに対する順電流通電効果

徳田豊, 吉田光, 冨田一義, 加地徹, 伊藤成志, 八木孝秀

応用物理学会学術講演会講演予稿集 2021.1 巻 ( 0 ) 頁： 2427 - 2427 2021年2月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2021.1.0_2427

CiNii Research
順電流注入によるp-GaN 層中のホールトラップの生成

吉田光, 竹内和歌奈, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2021.1 巻 ( 0 ) 頁： 2428 - 2428 2021年2月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2021.1.0_2428

CiNii Research
Why do electron traps atE(C)-0.6 eV have inverse correlation with carbon concentrations in n-type GaN layers? 査読有り国際誌

Narita Tetsuo, Horita Masahiro, Tomita Kazuyoshi, Kachi Tetsu, Suda Jun

JAPANESE JOURNAL OF APPLIED PHYSICS 59 巻 ( 10 ) 2020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）出版者・発行元：JAPANESE JOURNAL OF APPLIED PHYSICS

Web of Science
Progress on and challenges of p-type formation for GaN power devices 招待有り査読有り国際共著国際誌

Narita Tetsuo, Yoshida Hikaru, Tomita Kazuyoshi, Kataoka Keita, Sakurai Hideki, Horita Masahiro, Bockowski Michal, Ikarashi Nobuyuki, Suda Jun, Kachi Tetsu, Tokuda Yutaka

JOURNAL OF APPLIED PHYSICS 128 巻 ( 9 ) 2020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）出版者・発行元：Journal of Applied Physics

The fabrication processes of p-type regions for vertical GaN power devices are investigated. A p-type body layer in a trench gate metal-oxide-semiconductor field-effect transistor requires precise control of the effective acceptor concentration, which is equal to the difference between the Mg acceptor concentration (Na) and the compensating donor concentration (Nd). The carbon atoms incorporated during growth via metalorganic vapor phase epitaxy substitute nitrogen sites (CN) and function as donor sources in a p-type GaN layer. Since interstitial H atoms (H i) also compensate holes, their removal from an Mg-doped layer is crucial. Extended anneals to release H atoms cause the formation of extra hole traps. The p+ capping layer allows effective and rapid removal of H atoms from a p-type body layer owing to the electric field across the p+/p- junction. On the other hand, selective area p-type doping via Mg ion implantation is needed to control the electrical field distribution at the device edge. Ultrahigh-pressure annealing (UHPA) under a nitrogen pressure of 1 GPa enables post-implantation annealing up to 1753 K without thermal decomposition. Cathodoluminescence spectra and Hall-effect measurements suggest that the acceptor activation ratio improves dramatically by annealing above 1673 K as compared to annealing at up to 1573 K. High-temperature UHPA also induces Mg atom diffusion. We demonstrate that vacancy diffusion and the introduction of H atoms from the UHPA ambient play a key role in the redistribution of Mg atoms.

DOI： 10.1063/5.0022198

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Heイオン注入によりMOVPE成長p-GaNに生成されたトラップ評価

徳田豊, 吉田光, 冨田一義, 加地徹, 伊藤成志, 八木孝秀

応用物理学会学術講演会講演予稿集 2020.2 巻 ( 0 ) 頁： 1911 - 1911 2020年8月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2020.2.0_1911

CiNii Research
長時間熱処理されたMOVPE p-GaNの順バイアスDLTS測定

吉田光, 竹内和歌奈, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2020.2 巻 ( 0 ) 頁： 1908 - 1908 2020年8月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2020.2.0_1908

CiNii Research
Dual-color-sub-bandgap-light-excited isothermal capacitance transient spectroscopy for quick measurement of carbon-related hole trap density in n-type GaN 査読有り国際誌

Kanegae Kazutaka, Narita Tetsuo, Tomita Kazuyoshi, Kachi Tetsu, Horitata Masahiro, Kimoto Tsunenobu, Suda Jun

JAPANESE JOURNAL OF APPLIED PHYSICS 59 巻 ( SG ) 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）出版者・発行元：Japanese Journal of Applied Physics

A quick method is proposed for measurement of the carbon-related hole trap (H1: +0.87 eV) density in an n-type GaN homoepitaxial layer using dual-color-sub-bandgap-light-excited isothermal capacitance transient spectroscopy. Shorter wavelength (390 nm) light irradiation is employed to cause the hole traps to be in the hole-occupied state. Longer wavelength (660 nm) light irradiation is then used to emit the hole from the trap to the valence band. The photoemission of holes is much quicker than the thermal emission, which reduces the measurement time. The trap density can be calculated from the capacitance transient.

DOI： 10.35848/1347-4065/ab6863

Web of Science

Scopus
高温熱処理されたMOVPE p-GaNの浅い準位の評価

吉田光, 寺部知世, 安井裕喜, 竹内和歌奈, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2020.1 巻 ( 0 ) 頁： 2799 - 2799 2020年2月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2020.1.0_2799

CiNii Research
Overview of carrier compensation in GaN layers grown by MOVPE: toward the application of vertical power devices 招待有り査読有り国際誌

Narita Tetsuo, Tomita Kazuyoshi, Kataoka Keita, Tokuda Yutaka, Kogiso Tatsuya, Yoshida Hikaru, Ikarashi Nobuyuki, Iwata Kenji, Nagao Masahiro, Sawada Naoki, Horita Masahiro, Suda Jun, Kachi Tetsu

JAPANESE JOURNAL OF APPLIED PHYSICS 59 巻 ( SA ) 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）出版者・発行元：Japanese Journal of Applied Physics

Sources of carrier compensation in n-type and p-type GaN layers grown by metalorganic vapor phase epitaxy were quantitatively identified by a combination of Hall-effect analysis and deep level transient spectroscopy. For n-type GaN, we identified three electron compensation sources: Residual carbon atoms likely sitting on nitrogen sites (CN), an electron trap at the energy level of E C-0.6 eV (the E3 trap), and self-compensation appearing with increasing donor concentration. We showed that the CN also play a key role in hole compensation in p-type GaN by forming donor-like charged states. We also investigated the reduction of acceptor concentrations (N a) in highly Mg-doped GaN. Atomic-resolution scanning transmission electron microscopy revealed that electrically inactive Mg atoms of 3/2 atomic layers are segregated at the boundary of pyramidal inversion domains. The N a reduction can be explained by this Mg segregation.

DOI： 10.7567/1347-4065/ab4610

Web of Science

Scopus
GaN基板上MOVPE p-GaNのHd (Ev+0.88 eV)トラップ濃度面内分布

吉田光, 竹内和歌奈, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2019.2 巻 ( 0 ) 頁： 3216 - 3216 2019年9月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2019.2.0_3216

CiNii Research
Characterization of hole traps in MOVPE-grown p-type GaN layers using low-frequency capacitance deep-level transient spectroscopy 査読有り国際誌

Kogiso Tatsuya, Narita Tetsuo, Yoshida Hikaru, Tokuda Yutaka, Tomita Kazuyoshi, Kachi Tetsu

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 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）出版者・発行元：Japanese Journal of Applied Physics

Traps in MOVPE-grown Mg-doped GaN samples composed of p+/p-/n+ structures were investigated using low-frequency capacitance deep-level transient spectroscopy (DLTS). A drop-off in capacitance with decreasing temperature was observed. This is caused by the longer RC time constant of the diode with lower temperature, which is due to a decrease in the number of ionized Mg acceptors (which have a high ionization energy). This limits the use of lower temperatures in DLTS measurements. To extend DLTS to a lower temperature (105 K), DLTS using a capacitance measurement frequency of 1 kHz was applied. Thus, we can quantitatively discuss concentrations of traps with shallow energy levels. We obtained a nearly one-to-one relation between Ha (E V +0.29 eV) and Hd (E V +0.88 eV) in the p-type layer, which strongly supports the theoretical calculation that a carbon on a nitrogen site forms donor-like (Ha) and acceptor-like (Hd) states.

DOI： 10.7567/1347-4065/ab0408

Web of Science

Scopus
Atomic resolution structural analysis of magnesium segregation at a pyramidal inversion domain in a GaN epitaxial layer 査読有り

Iwata Kenji, Narita Tetsuo, Nagao Masahiro, Tomita Kazuyoshi, Kataoka Keita, Kachi Tetsu, Ikarashi Nobuyuki

APPLIED PHYSICS EXPRESS 12 巻 ( 3 ) 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/ab04f1

Web of Science

Scopus
GaN基板上MOVPE p-GaNの浅い準位の評価

吉田光, 小木曽達也, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2019.1 巻 ( 0 ) 頁： 2911 - 2911 2019年2月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2019.1.0_2911

CiNii Research
Quantitative investigation of the lateral diffusion of hydrogen in p-type GaN layers having NPN structures 査読有り国際誌

Narita Tetsuo, Tomita Kazuyoshi, Yamada Shinji, Kachi Tetsu

APPLIED PHYSICS EXPRESS 12 巻 ( 1 ) 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）

DOI： 10.7567/1882-0786/aaf418

Web of Science

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

Narita Tetsuo, Tomita Kazuyoshi, Tokuda Yutaka, Kogiso Tatsuya, Horita Masahiro, Kachi Tetsu

JOURNAL OF APPLIED PHYSICS 124 巻 ( 21 ) 2018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： 10.1063/1.5057373

Web of Science

Scopus
Wide range doping control and defect characterization of GaN layers with various Mg concentrations 査読有り国際誌

Narita Tetsuo, Ikarashi Nobuyuki, Tomita Kazuyoshi, Kataoka Keita, Kachi Tetsu

JOURNAL OF APPLIED PHYSICS 124 巻 ( 16 ) 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）出版者・発行元：JOURNAL OF APPLIED PHYSICS

DOI： 10.1063/1.5045257

Web of Science
GaN基板上MOVPE p-GaNの炭素関連トラップ

小木曽達也, 吉田光, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2018.2 巻 ( 0 ) 頁： 3036 - 3036 2018年9月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2018.2.0_3036

CiNii Research
異なる気相成長法によるGaN基板上n-GaN中トラップの比較

伊藤俊, 徳田豊, 成田哲生, 木村大至, 中村大輔, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2018.2 巻 ( 0 ) 頁： 2994 - 2994 2018年9月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2018.2.0_2994

CiNii Research
The trap states in lightly Mg-doped GaN grown by MOVPE on a freestanding GaN substrate 査読有り

Narita Tetsuo, Tokuda Yutaka, Kogiso Tatsuya, Tomita Kazuyoshi, Kachi Tetsu

JOURNAL OF APPLIED PHYSICS 123 巻 ( 16 ) 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： 10.1063/1.5010849

Web of Science

Scopus
低周波容量DLTS測定によるMOCVD p-GaNのトラップ評価

小木曽達也, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2018.1 巻 ( 0 ) 頁： 3320 - 3320 2018年3月

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記述言語：日本語出版者・発行元：公益社団法人応用物理学会

DOI： 10.11470/jsapmeeting.2018.1.0_3320

CiNii Research

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論文の先頭へ▲

講演・口頭発表等 3

Polarization Engineering in AlSiO/p-type GaN MOSFETs Using AIN Interlayers Formed by Plasma-Enhanced Atomic Layer Deposition 国際会議

Ito K., Narita T., Iguchi H., Iwasaki S., Kikuta D., Kano E., Ikarashi N., Tomita K., Horita M., Suda J.

Technical Digest - International Electron Devices Meeting, IEDM 2023年 Technical Digest - International Electron Devices Meeting, IEDM

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記述言語：英語会議種別：口頭発表（一般）

Polarization engineering by AIN interlayers (AlN-ILs) deposited via plasma-enhanced atomic layer deposition was demonstrated in AlSiO/p-type GaN MOSFETs. Transmission electron microscopy observations revealed that the AlN-ILs were grown on GaN epitaxially and therefore could induce polarization charges, similar to AlGaN/GaN. The decrease in the threshold voltage (Vth) with increasing AIN-IL thickness corresponded to the polarization charge density. In addition, insertion of the AIN-IL suppressed the positive bias instability by less than 0.05 V. By controlling the AIN-IL thickness and the channel p-type doping, we controlled the Vth the range from -3 to 5 V and achieved enhanced channel mobility compared with that for the corresponding MOSFET without an AIN-IL.

DOI： 10.1109/IEDM45741.2023.10413714

Scopus
DLTS測定によるGaN基板上MOCVDp++p-n+GaNのトラップ評価

小木曽達也, 上田聖悟, 徳田豊, 成田哲生, 富田一義, 加地徹

応用物理学会学術講演会講演予稿集 2017年3月1日公益社団法人応用物理学会

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記述言語：日本語会議種別：口頭発表（一般）

DOI： 10.11470/jsapmeeting.2017.1.0_3144

CiNii Research
GaN基板上MOCVD p-GaNの電子トラップ

小木曽達也, 徳田豊, 成田哲生, 冨田一義, 加地徹

応用物理学会学術講演会講演予稿集 2017年8月25日公益社団法人応用物理学会

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記述言語：日本語会議種別：口頭発表（一般）

DOI： 10.11470/jsapmeeting.2017.2.0_3085

CiNii Research

講演・口頭発表等の先頭へ▲