Faculty Profiles - HORITA Masahiro

Free electron mobility limited by fixed charges and trapped electrons in 4H-SiC (1120) and (1100) MOSFETs annealed in NO

Ito, K; Tanaka, H; Horita, M; Suda, J; Kimoto, T

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 64 ( 1 ) 2025.1

Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

The impact of Coulomb scattering by fixed charges and trapped electrons on the free electron mobility (μfree) of SiC(11 2 ¯ 0) and (1 1 ¯ 00) MOSFETs annealed in NO was quantitatively discussed through numerical calculations. The fixed charge density for MOSFETs on (11 2 ¯ 0) and (1 1 ¯ 00) annealed in NO was estimated to be 1.0 × 1013 cm−2, which is four times higher than that for (0001) MOSFETs previously reported. Calculation of μfree can well reproduce the experimental Hall mobilities for all MOSFETs on (11 2 ¯ 0) and (1 1 ¯ 00) within the wide range of effective normal field (0.08 MV cm−1 ≤ Eeff ≤ 0.78 MV cm−1).

DOI： 10.35848/1347-4065/ada1b7

Engineered interface charges and traps in GaN MOSFETs providing high channel mobility and E-mode operation Open Access

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 12 ) 2024.12

Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

This review focuses on controlling interface charges and traps to obtain minimal channel resistance and stable enhancement-mode operation in GaN MOSFETs. Interface traps reduce the free electron density and act as Coulomb scattering centers, thus reducing the channel mobility. Oxide traps cause instability of threshold voltage (Vth) by trapping electrons or holes under gate bias. In addition, the Vth is affected by the overall distribution of interface charges. The first key is a design of a bilayer structure to simultaneously obtain good insulating properties and interface properties. The other key is the optimization of post-deposition annealing to minimize oxide traps and interface fixed charges. Consequently, the gate structure of an AlSiO/AlN/p-type GaN has been designed. Reductions in Vth as a result of polarization charges can be eliminated using an m-plane trench channel, resulting in a channel mobility of 150 cm2 V-1s-1 and Vth of 1.3 V.

DOI： 10.35848/1347-4065/ad8c4f

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

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

PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS Vol. 18 ( 12 ) 2024.12

Publisher：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

Impact of Coulomb scattering due to trapped electrons on Hall mobilities in 4H-SiC (11(2)over-bar0) and (1(1)over-bar00) MOSFETs annealed in NO

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 11 ) 2024.11

Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

The temperature dependence of Hall mobility (μ Hall) of 4H-SiC(11 2 ¯ 0) and (1 1 ¯ 00) metal-oxide-semiconductor field-effect transistors (MOSFETs) with the gate oxides annealed in NO is compared with that of MOSFETs on (0001) annealed in NO or POCl3. Coulomb scattering due to trapped electrons, which is reported to be significant in MOSFETs on (0001) annealed in NO, may be the primary limiting factor of μ Hall for MOSFETs on (11 2 ¯ 0) and (1 1 ¯ 00) annealed in NO. Furthermore, the difference in μ Hall among the MOSFETs is highlighted at 77 K, which may be attributed to the suppression of phonon scattering and the presence of strong Coulomb scattering.

DOI： 10.35848/1347-4065/ad879d

A distinctive bound exciton line induced by electron-beam irradiation and subsequent annealing of an unintentionally doped GaN layer

Iguchi, H; Kataoka, K; Horita, M; Narita, T; Yamada, S; Tomita, K; Kachi, T; Suda, J

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 11 ) 2024.11

Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

An undefined bound exciton line (UDX) with a photon energy 0.6 meV lower than the Si-donor bound exciton line was observed by photoluminescence in gallium nitride (GaN) layers annealed at 1100 °C after electron beam (EB) irradiation at an energy of 137-2000 keV. The UDX was not observed in samples not subjected to EB irradiation or annealing but was found in a sample annealed after EB irradiation at an energy of 137 keV, where only nitrogen atoms are displaced in GaN. The origin of the UDX was presumably formed by a thermal reaction of defects containing nitrogen-displacement-related defects.

DOI： 10.35848/1347-4065/ad918a

Influence of fixed charges and trapped electrons on free electron mobility at 4H-SiC(0001)/SiO2 interfaces with gate oxides annealed in NO or POCl3 Open Access

Ito, K; Tanaka, H; Horita, M; Suda, J; Kimoto, T

APPLIED PHYSICS EXPRESS Vol. 17 ( 8 ) 2024.8

Publisher：Applied Physics Express

Free electron mobility (μ free) in 4H-SiC(0001) MOSFETs with gate oxides annealed in NO or POCl3 was calculated in a wide range of effective normal field (E eff) from 0.02 to 2 MV cm−1, taking account of scattering by fixed charges and trapped electrons. The present calculation indicates that the Hall mobility in the high-E eff region experimentally obtained for NO-annealed MOSFETs (14 cm2 V−1 s−1 at 1.1 MV cm−1) is much lower than that for POCl3-annealed MOSFETs (41 cm2 V−1 s−1) due to severe Coulomb scattering by electrons trapped at a very high density of interface states.

DOI： 10.35848/1882-0786/ad63ef

Nitrogen-displacement-related recombination centers generated by electron beam irradiation in n-type and p-type homoepitaxial GaN layers Reviewed Open Access

Endo, M; Horita, M; Suda, J

APPLIED PHYSICS EXPRESS Vol. 17 ( 1 ) 2024.1

Language：English Publisher：Applied Physics Express

Recombination centers originating from point defects generated by the displacement of N atoms in n-type and p-type GaN were investigated by analyzing Shockley-Read-Hall (SRH) recombination currents in homoepitaxial GaN p-n junctions. These defects were intentionally generated by electron beam (EB) irradiation at 137 keV. The net doping concentrations in p+-n junction diodes were not changed following irradiation although the levels in p-n+ junction diodes decreased as the EB fluence was increased. The SRH recombination current also increased with increases in the fluence. This work additionally evaluated the relationship between recombination lifetimes and trap concentrations obtained by deep level transient spectroscopy.

DOI： 10.35848/1882-0786/ad16ad

High Hall electron mobility in the inversion layer of 4H-SiC (0001)/SiO2 interfaces annealed in POCl3 Reviewed

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

APPLIED PHYSICS EXPRESS Vol. 16 ( 7 ) 2023.7

Language：English Publisher：Applied Physics Express

Hall effect measurements were conducted for MOSFETs with and without post-oxidation-annealing (POA) fabricated on the p-body doping in a wide doping range to vary the effective normal field (E eff). The Hall mobility (μ Hall) in the high-E eff region of the MOSFETs annealed in phosphoryl chloride (μ Hall = 41 cm2 V−1 s−1 at E eff = 1.1 MV cm−1) is much higher than that of MOSFETs annealed in nitric oxide (NO) (μ Hall = 14 cm2 V−1 s−1 at E eff = 1.1 MV cm−1), suggesting that the trapped electrons act as strong Coulomb scattering centers for the MOSFETs annealed in NO and without POA.

DOI： 10.35848/1882-0786/ace150

Correlation between non-ionizing energy loss and production rate of electron trap at EC - (0.12-0.20) eV formed in gallium nitride by various types of radiation Reviewed

Aoshima, K; Horita, M; Suda, J

APPLIED PHYSICS LETTERS Vol. 122 ( 1 ) 2023.1

Language：English Publisher：Applied Physics Letters

Production rate (PR = trap concentration/incident fluence) of traps formed by energetic particles is important for predicting device degradation caused by radiation when developing radiation-resistant devices. We demonstrate a clear correlation between non-ionizing energy loss (NIEL) and PR of an electron trap at about 0.12-0.20 eV below the conduction band edge [EC - (0.12-0.20) eV] for various types of energetic particles in gallium nitride (GaN). NIEL values in GaN for electrons, protons, and α-rays were calculated using a screened-relativistic treatment, and NIEL values for gamma-rays were calculated by simulating slowed-down spectra due to shielding material. To obtain the PRs of the electron trap, 60Co gamma-rays with an average photon energy of 1.25 MeV and electron beams with energies from 137 keV to 2 MeV were irradiated onto n-type GaN Schottky barrier diodes. We measured the concentration of an electron trap at EC - (0.13-0.14) eV using deep-level transient spectroscopy. We also used the PRs of electron traps with similar energy levels of EC - (0.12-0.20) eV from previous studies on electrons, protons, and α-rays irradiated on GaN. All the trap PRs were proportional to the NIEL in a range of eight orders of magnitude, which confirms that the energy levels formed by various energetic particles have the same origin of being generated by atomic displacements. The obtained relationship coefficient between the NIEL and PRs of the trap is useful for predicting the degradation of GaN-based devices due to traps formed by various kinds of radiation.

DOI： 10.1063/5.0128709

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

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

Language：English Publisher：Technical Digest - International Electron Devices Meeting, IEDM

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

Depth profiling of E <inf>C</inf> - 0.26 eV electron traps introduced in homoepitaxial n-type GaN by ultra-low-dose Si-ion implantation and subsequent annealing Reviewed

Iguchi H., Horita M., Suda J.

Applied Physics Express Vol. 15 ( 12 ) 2022.12

Language：English Publisher：Applied Physics Express

Si ions were implanted into homoepitaxial n-type GaN at a peak concentration of 3 × 1014 cm−3 with subsequent annealing, and the associated formation of electron traps was investigated in detail using deep-level transient spectroscopy. A major electron trap was identified as 0.26 eV below the conduction band minimum and this trap concentration increased with increasing post-implantation annealing temperature, to a value of 6-8 × 1015 cm−3. Significant increases in the net donor concentration (N D) were also observed within the implanted region. The profile of the electron trap concentration was correlated with these increases in N D, suggesting that these traps acted as donors.

DOI： 10.35848/1882-0786/aca45d

Process engineering of GaN power devices via selective-area p-type doping with ion implantation and ultra-high-pressure annealing Reviewed Open Access

Kachi, T; Narita, T; Sakurai, H; Matys, M; Kataoka, K; Hirukawa, K; Sumida, K; Horita, M; Ikarashi, N; Sierakowski, K; Bockowski, M; Suda, J

JOURNAL OF APPLIED PHYSICS Vol. 132 ( 13 ) 2022.10

Language：English Publisher：Journal of Applied Physics

P-type doping in selected areas of gallium nitride (GaN) using magnesium (Mg)-ion implantation and subsequent ultra-high-pressure annealing (UHPA) are investigated to improve the performance of vertical GaN power devices. UHPA allows a high-temperature process without decomposition of the GaN surface and virtually complete activation of the implanted Mg ions in GaN. In the present paper, we provide an overview of recent challenges in making UHPA more realistic as an industrial process. Instead of UHPA at more than 1400 °C for a short duration, prolonged UHPA at 1300 °C demonstrates a comparable acceptor activation of Mg-ion-implanted GaN. This can reduce the annealing pressure to approximately 300 MPa and enlarge the processable wafer diameter. The second challenge is controlling the doping profiles in the lateral and vertical directions. We demonstrate fine patterning of the p-type regions, which indicates the limited lateral diffusion of Mg through UHPA. However, controlling the vertical doping profile is challenging. The nitrogen vacancies formed by ion implantation reduce the effective acceptor concentration near the surface, which can be compensated for by sequential nitrogen ion implantation. Defect-assisted Mg diffusion to the deeper region causes a redistribution of the Mg atoms and should be considered in the design of a device. Such anisotropic diffusion of Mg to the c-axis has potential applications in the fabrication of unique vertical device structures such as super junctions.

DOI： 10.1063/5.0107921

Effective channel mobility in phosphorus-treated 4H-SiC (0001) metal-oxide-semiconductor field-effect transistors with various p-body doping concentrations Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( 9 ) 2022.9

Language：English Publisher：Japanese Journal of Applied Physics

Phosphorus treatment, which can substantially reduce the interface state density (D it), was used to investigate the impact of D it on effective channel mobility (μ eff) of 4H-SiC (0001) metal-oxide-semiconductor field-effect transistors (MOSFETs). A high μ eff of 126 cm2 V-1 s-1, which exceeds the reported phonon-limited mobility of 83 cm2 V-1 s-1 determined from Hall mobility of nitridation-treated MOSFETs, at a high effective normal field of 0.57 MV cm-1 was obtained in MOSFETs fabricated on a high-purity semi-insulating 4H-SiC substrate at room temperature. This high mobility may be caused by the difference of the density of electrons trapped at the interface states.

DOI： 10.35848/1347-4065/ac87e4

Increase in net donor concentration due to introduction of donor-like defects by ultra-low-dose Si-ion implantation and subsequent annealing in homoepitaxial n-type GaN Reviewed

Iguchi, H; Horita, M; Suda, J

APPLIED PHYSICS EXPRESS Vol. 15 ( 7 ) 2022.7

Language：English Publisher：Applied Physics Express

Si ions were implanted at a dose of 1 × 1010 cm-2 into a homoepitaxial n-type GaN layer with a net donor concentration (N D) of 3-8 × 1015 cm-3. The N D in the implanted region increased by 1-3 × 1015 cm-3 after annealing at a temperature greater than 900 °C compared with that for the as-grown homoepitaxial layer. The increase in N D was considerably larger than the peak concentration of implanted Si ions (3 × 1014 cm-3). No increase in N D was observed for an as-grown sample after annealing. These results clearly suggest that donor-like defects were introduced by implantation of Si ions and a subsequent annealing process.

DOI： 10.35848/1882-0786/ac7433

SiO2/GaN interfaces with low defect densities and high breakdown electric fields formed by plasma-enhanced atomic layer deposition Reviewed Open Access

Aoshima, K; Taoka, N; Horita, M; Suda, J

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( SC ) 2022.5

Language：English Publisher：Japanese Journal of Applied Physics

We present SiO2/GaN interfaces with a low interface state density and a high breakdown electric field. The SiO2 films were deposited by plasma-enhanced atomic layer deposition (ALD) using bis(diethylamino)silane and O2 plasma at 300 °C on n-type GaN (0001) homoepitaxial layers. An interface state density of less than 1011 cm-2 eV-1 at 0.3 eV below the conduction band edge was confirmed by the conductance method. The value is much lower than those of previously reported ALD-SiO2/GaN interfaces (1012-1013 cm-2 eV-1). A low fixed charge density at the SiO2/GaN interface of 3.7 × 1011 cm-2 and a high dielectric breakdown field of ∼10 MV cm-1 were obtained. Moreover, the interface state density and current-voltage characteristics were further improved by post-deposition annealing at 400 °C in N2 ambient. Scanning transmission electron microscopy with energy-dispersive X-ray analysis revealed the existence of a GaO x interlayer between SiO2 and GaN. The unintentionally formed interlayer could be one of the reasons for the improvement of interface properties at ALD-SiO2/GaN.

DOI： 10.35848/1347-4065/ac4f79

Endo, M; Horita, M; Suda, J

APPLIED PHYSICS LETTERS Vol. 120 ( 14 ) 2022.4

Language：English Publisher：Applied Physics Letters

This work investigated deep levels in p-type GaN originating from intrinsic point defects, using deep level transient spectroscopy (DLTS) to examine homoepitaxial GaN p+-p-n+ junction diodes grown via metalorganic vapor-phase epitaxy. Following exposure to an electron beam with an energy of 137 keV that generated nitrogen vacancies (VN) and nitrogen interstitials (NI), a peak due to EHa hole traps (at 0.52 eV) was observed in DLTS spectra. The injection of minority carriers resulting from applying a forward bias generated signals for EHb (0.5 eV) and EHc (0.8 eV) hole traps while decreasing the EHa signal and increasing the net accepter concentration. The generation of EHa traps can likely be attributed to VN (3+/+) or NI (2+/+) defects based on the results of first-principles calculations. The EHb and EHc hole traps may have been associated with complex defects, including those that generated EHa traps, because these two traps appeared as the concentration of EHa traps decreased.

DOI： 10.1063/5.0086535

Breakdown Electric Field of GaN p+-n and p-n+ Junction Diodes With Various Doping Concentrations Reviewed

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

IEEE ELECTRON DEVICE LETTERS Vol. 43 ( 1 ) page： 96 - 99 2022.1

Language：English Publisher：IEEE Electron Device Letters

Breakdown characteristics in homoepitaxial GaN p-n junction diodes with p+-n and p-n+ junctions with relatively heavy doping concentrations are systematically investigated. The devices have vertical deep mesa etch termination, which enables uniform (nearly ideal) avalanche breakdown without electric field (E-field) crowding at the device edge. For p+-n junction, breakdown E-field of 3.0, 3.3 and 3.8 MV/cm and breakdown voltage (BV) of 340, 207 and 128 V were achieved at the donor concentrations of 7.5 × 1016, 1.5 × 1017, 3.1× 1017 cm-3, respectively. For p-n+ junction, breakdown E-field of 3.2, 3.3 and 4.0 MV/cm and BV of 235, 180 and 110 V were achieved at the acceptor concentrations of 1.3 × 1017, 1.8 × 1017, 4.1 × 1017 cm-3, respectively. No significant difference of the breakdown characteristics between n-type and p-type voltage-blocking layers was observed. These results are consistent with numerical simulations using impact ionization coefficients (IICs) in GaN reported in our previous studies.

DOI： 10.1109/LED.2021.3125328

Effect of annealing time and pressure on electrical activation and surface morphology of Mg-implanted GaN annealed at 1300 °C in ultra-high-pressure nitrogen ambient Reviewed

Sumida, K; Hirukawa, K; Sakurai, H; Sierakowski, K; Horita, M; Bockowski, M; Kachi, T; Suda, J

APPLIED PHYSICS EXPRESS Vol. 14 ( 12 ) 2021.12

Language：English Publisher：Applied Physics Express

We performed an isothermal annealing study on Mg-implanted GaN at 1300 °C in an ultra-high-pressure (1 GPa) nitrogen ambient. Annealing for more than 30 min resulted in a high acceptor activation ratio and a low compensation ratio that were comparable to those obtained with annealing at 1400 °C for 5 min. We also performed annealing at 1300 °C in a reduced nitrogen pressure of 300 MPa which makes us possible to expand the inner diameter of annealing equipment in the future. High electrical activation, similar to one obtained by annealing at 1 GPa, was successfully obtained.

DOI： 10.35848/1882-0786/ac39b0

Effect of Schottky barrier height on quantitative analysis of deep-levels in n-type GaN by deep-level transient spectroscopy Reviewed Open Access

Aoshima, K; Horita, M; Suda, J

AIP ADVANCES Vol. 11 ( 11 ) 2021.11

Language：English Publisher：AIP Advances

Deep-level transient spectroscopy (DLTS) using Schottky barrier diodes (SBDs) is widely used for quantitative analysis of deep levels. This study focuses on the dependence of Schottky barrier height on apparent time constants and concentrations of electron traps in n-type GaN. DLTS using SBDs with various barrier heights was carried out. Experimental data show that large reverse leakage currents due to low barrier heights resulted in underestimation of time constants and concentrations. Theoretical calculations considering the impact of leakage currents reproduced experimental results well. Based on the calculations, we suggest a minimum required barrier height where accurate time constants and concentrations can be evaluated.

DOI： 10.1063/5.0073747

Effects of the sequential implantation of Mg and N ions into GaN for p-type doping Reviewed

Sakurai, H; Narita, T; Kataoka, K; Hirukawa, K; Sumida, K; Yamada, S; Sierakowski, K; Horita, M; Ikarashi, N; Bockowski, M; Suda, J; Kachi, T

APPLIED PHYSICS EXPRESS Vol. 14 ( 11 ) 2021.11

Language：English Publisher：Applied Physics Express

The sequential implantation of Mg and N ions into GaN was investigated using conventional rapid thermal annealing and ultra-high-pressure annealing (UHPA). In cathodoluminescence, the green luminescence related to nitrogen vacancies (VNs) was mostly suppressed at the Mg/N ratio of 0.5-1.0, whereas the donor-acceptor pair (DAP) emission as a signature of Mg acceptors was maintained high. The excess N implantation reduced the DAP emission through the formation of nonradiative recombination centers. The combined process of optimal Mg/N implantation and UHPA at 1673 K improved ohmic contacts by increasing Mg concentration and suppressing VNs near the surface.

DOI： 10.35848/1882-0786/ac2ae7

Investigation of point defects in GaN for the realization of high performance GaN vertical power devices Reviewed

SUDA Jun, HORITA Masahiro, KANEGAE Kazutaka

Oyo Buturi Vol. 90 ( 10 ) page： 628 - 631 2021.10

Language：Japanese Publisher：The Japan Society of Applied Physics

Fundamental knowledge of point defects is essential for developing epitaxial growth, device processes and device design and characterization. However, the knowledge with regard to GaN is quite limited compared to Si and GaAs. The authors have carried out an extensive investigation of point defects in GaN by using deep-level transient spectroscopy (DLTS). In this paper, the origin of the E3 trap, the development of quantitative measurement techniques for carbon-related hole traps in GaN by using sub-bandgap photoexcitation and studies of nitrogen-displacement-related point defects (nitrogen vacancy and interstitial) intentionally formed by electron beam irradiation are reviewed.

DOI： 10.11470/oubutsu.90.10_628

CiNii Research

Depth profiles of electron traps generated during reactive ion etching in n-type 4H-SiC characterized by using isothermal capacitance transient spectroscopy Reviewed

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

JOURNAL OF APPLIED PHYSICS Vol. 130 ( 10 ) 2021.9

Language：English Publisher：Journal of Applied Physics

Electron traps generated during the reactive ion etching (RIE) process in n-type 4H-SiC are investigated using the deep-level transient spectroscopy technique and isothermal capacitance transient spectroscopy (ICTS) technique. Two electron traps of the Z1/2 center are detected in the RIE-etched sample by ICTS measurement at 300 K. A method is proposed to determine the depth profiles of the electron traps that are localized near the etched surface, whereby a depth profile is extracted from the dependence of averaged trap density on the depletion layer width. An exponential distribution is assumed as the depth profile of the electron traps generated during the RIE process. The extracted depth profile was confirmed to be consistent with that determined by the double-correlation method. An appropriate function for the depth profile of carrier traps is assumed and the dependence of the averaged trap density on the depletion layer width is analyzed, which enables the extraction of a depth profile that has both higher depth resolution and higher resolution in the carrier trap density with the proposed method than that with the double-correlation method.

DOI： 10.1063/5.0059588

Photoionization cross section ratio of nitrogen-site carbon in GaN under sub-bandgap-light irradiation determined by isothermal capacitance transient spectroscopy Reviewed

Kanegae, K; Narita, T; Tomita, K; Kachi, T; Horita, M; Kimoto, T; Suda, J

APPLIED PHYSICS EXPRESS Vol. 14 ( 9 ) 2021.9

Language：English Publisher：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

Impact ionization coefficients and critical electric field in GaN Reviewed

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

JOURNAL OF APPLIED PHYSICS Vol. 129 ( 18 ) 2021.5

Language：English Publisher：Journal of Applied Physics

Avalanche multiplication characteristics in a reverse-biased homoepitaxial GaN p-n junction diode are experimentally investigated at 223-373 K by novel photomultiplication measurements utilizing above- and below-bandgap illumination. The device has a non-punch-through one-side abrupt p--n+ junction structure, in which the depletion layer mainly extends to the p-type region. For above-bandgap illumination, the light is absorbed at the surface p+-layer, and the generated electrons diffuse and reach the depletion layer, resulting in an electron-injected photocurrent. On the other hand, for below-bandgap illumination, the light penetrates a GaN layer and is absorbed owing to the Franz-Keldysh effect in the high electric field region (near the p-n junction interface), resulting in a hole-induced photocurrent. The theoretical (non-multiplicated) photocurrents are calculated elaborately, and the electron- and hole-initiated multiplication factors are extracted as ratios of the experimental data to the calculated values. Through the mathematical analyses of the multiplication factors, the temperature dependences of the impact ionization coefficients of electrons and holes in GaN are extracted and formulated by the Okuto-Crowell model. The ideal breakdown voltage and the critical electric field for GaN p-n junctions of varying doping concentration are simulated using the obtained impact ionization coefficients, and their temperature dependence and conduction-type dependence were discussed. The simulated breakdown characteristics show good agreement with data reported previously, suggesting the high accuracy of the impact ionization coefficients obtained in this study.

DOI： 10.1063/5.0050793

Isochronal annealing study of Mg-implanted p-type GaN activated by ultra-high-pressure annealing Reviewed

Hirukawa, K; Sumida, K; Sakurai, H; Fujikura, H; Horita, M; Otoki, Y; Sierakowski, K; Bockowski, M; Kachi, T; Suda, J

APPLIED PHYSICS EXPRESS Vol. 14 ( 5 ) 2021.5

Language：English Publisher：Applied Physics Express

Isochronal annealing was performed on Mg-ion-implanted GaN under 1 GPa N2 ambient pressure for 5 min at temperatures of 1573-1753 K. Secondary ion mass spectrometry showed diffusion of Mg atoms and introduction of H atoms during annealing. Deeper diffusion was observed with increasing temperature. From Hall-effect measurements, p-type conductivity was found even for the sample with the lowest annealing temperature of 1573 K. For this sample, the acceptor activation ratio was 23% and the compensation ratio was 93%. The acceptor activation ratio increased to almost 100% and the compensation ratio decreased to 12% with increasing annealing temperature.

DOI： 10.35848/1882-0786/abf4f3

Analysis of channel mobility in GaN-based metal-oxide-semiconductor field-effect transistors Reviewed

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

Journal of Applied Physics Vol. 129 ( 8 ) 2021.2

Nitrogen-displacement-related electron traps in n-type GaN grown on a GaN freestanding substrate Reviewed Open Access

Horita Masahiro, Narita Tetsuo, Kachi Tetsu, Suda Jun

Applied Physics Letters Vol. 118 ( 1 ) 2021.1

Impact of gamma-ray irradiation on capacitance-voltage characteristics of Al2O3/GaN MOS diodes with and without post-metallization annealing Reviewed

Aoshima Keito, Horita Masahiro, Suda Jun, Hashizume Tamotsu

Applied Physics Express Vol. 14 ( 1 ) 2021.1

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

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

Applied Physics Letters Vol. 117 ( 15 ) 2020.10

Why do electron traps atE(C)-0.6 eV have inverse correlation with carbon concentrations in n-type GaN layers? Reviewed

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

Japanese Journal of Applied Physics Vol. 59 ( 10 ) 2020.10

Progress on and challenges of p-type formation for GaN power devices Reviewed

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 Vol. 128 ( 9 ) 2020.9

Impacts of high temperature annealing above 1400°C under N<inf>2</inf>overpressure to activate acceptors in Mg-implanted GaN Reviewed

Sakurai H., Narita T., Hirukawa K., Yamada S., Koura A., Kataoka K., Horita M., Ikarashi N., Bockowski M., Suda J., Kachi T.

Proceedings of the International Symposium on Power Semiconductor Devices and ICs Vol. 2020-September page： 321 - 324 2020.9

Language：English Publisher：Proceedings of the International Symposium on Power Semiconductor Devices and ICs

In this study, we clarify the impact of annealing pressure and temperature of the ultra-high-pressure annealing (UHPA) as a post-implantation-annealing (PIA) on the acceptor activation for Mg-ions-implanted GaN samples. The pressure to prevent the thermal decomposition is absolutely determined by the equilibrium N2 partial pressure in the phase diagram of GaN-Ga-N2 system, so that the pressure below the critical pressure always leads to the serious surface decomposition of GaN. In low temperature cathodoluminescence examinations, the samples processed at 1400°C or above exhibited more intense emissions in the near band edge and donor-acceptor pair band with a suppression of green luminescence related to point defects. Temperature dependent Hall-effect measurement was allowed for the UHPA samples annealed at 1400°C or above, whereas free holes were not observed for the 1300°C-UHPA. Moreover, the acceptor concentrations (Na) for samples annealed at 1400°C or above were close to Mg concentrations. We thus revealed the key process parameters in UHPA, which is at more than 1400°C under the N2 overpressure exceeding the equilibrium partial pressure. These findings can play as a key role in the selective area doping using UHPA.

DOI： 10.1109/ISPSD46842.2020.9170174

Overview of carrier compensation in GaN layers grown by MOVPE: toward the application of vertical power devices Reviewed

Redistribution of Mg and H atoms in Mg-implanted GaN through ultra-high-pressure annealing Reviewed

Sakurai Hideki, Narita Tetsuo, Omori Masato, Yamada Shinji, Koura Akihiko, Iwinska Malgorzata, Kataoka Keita, Horita Masahiro, Ikarashi Nobuyuki, Bockowski Michal, Suda Jun, Kachi Tetsu

Applied Physics Express Vol. 13 ( 8 ) 2020.8

Identification of origin ofE(C)-0.6 eV electron trap level by correlation with iron concentration in n-type GaN grown on GaN freestanding substrate by metalorganic vapor phase epitaxy Reviewed

Horita Masahiro, Narita Tetsuo, Kachi Tetsu, Suda Jun

Applied Physics Express Vol. 13 ( 7 ) 2020.7

Dual-color-sub-bandgap-light-excited isothermal capacitance transient spectroscopy for quick measurement of carbon-related hole trap density in n-type GaN Reviewed Open Access

Kanegae K.

Japanese Journal of Applied Physics Vol. 59 ( SG ) 2020.4

Electron traps formed by gamma-ray irradiation in homoepitaxial n-type GaN and their annealing behavior Reviewed Open Access

Aoshima Keito, Kanegae Kazutaka, Horita Masahiro, Suda Jun

AIP Advances Vol. 10 ( 4 ) 2020.4

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 Vol. 59 ( SA ) 2020.1

Impacts of high temperature annealing above 1400 degrees C under N-2 overpressure to activate acceptors in Mg-implanted GaN Reviewed

Sakurai Hideki, Narita Tetsuo, Hirukawa Kazufumi, Yamada Shinji, Koura Akihiko, Kataoka Keita, Horita Masahiro, Ikarashi Nobuyuki, Bockowski Michal, Suda Jun, Kachi Tetsu

Proceedings of the 2020 32nd International Symposium on Power Semiconductor Devices and ICs (ISPSD 2020) page： 321 - 324 2020

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

Maeda T.

Technical Digest - International Electron Devices Meeting, IEDM Vol. 2019-December 2019.12

Highly effective activation of Mg-implanted p-type GaN by ultra-high-pressure annealing Reviewed

Sakurai Hideki, Omori Masato, Yamada Shinji, Furukawa Yukihiro, Suzuki Hideo, Narita Tetsuo, Kataoka Keita, Horita Masahiro, Bockowski Michal, Suda Jun, Kachi Tetsu

Applied Physics Letters Vol. 115 ( 14 ) 2019.9

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

Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

Applied Physics Letters Vol. 115 ( 14 ) 2019.9

Franz-Keldysh effect in 4H-SiC p-n junction diodes under high electric field along the < 11(2)over-bar0 > direction Reviewed

Maeda Takuya, Chi Xilun, Tanaka Hajime, Horita Masahiro, Suda Jun, Kimoto Tsunenobu

Japanese Journal of Applied Physics Vol. 58 ( 9 ) 2019.9

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

Kanegae Kazutaka, Fujikura Hajime, Otoki Yohei, Konno Taichiro, Yoshida Takehiro, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

Applied Physics Letters Vol. 115 ( 1 ) 2019.7

Shockley-Read-Hall lifetime in homoepitaxial p-GaN extracted from recombination current in GaN p-n(+) junction diodes Reviewed Open Access

Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

Japanese Journal of Applied Physics Vol. 58 ( SC ) 2019.6

Design and Fabrication of GaN p-n Junction Diodes With Negative Beveled-Mesa Termination Reviewed

Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

IEEE Electron Device Letters Vol. 40 ( 6 ) page： 941 - 944 2019.6

Acceptors activation of Mg-ion implanted GaN by ultra-high-pressure annealing Reviewed

Sakurai H.

19th International Workshop on Junction Technology, IWJT 2019 2019

Estimation of Impact Ionization Coefficient in GaN by Photomulitiplication Measurement Utilizing Franz-Keldysh Effect Reviewed

Maeda T.

Proceedings of the 2019 31st International Symposium on Power Semiconductor Devices and ICs Vol. 2019-May page： 59 - 62 2019

Impact Ionization Coefficients in GaN Measured by Above- and Sub-Eg Illuminations for p-/n+ Junction

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

2019 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM) 2019

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

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

JOURNAL OF APPLIED PHYSICS Vol. 124 ( 21 ) 2018.12

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

Maeda Takuya, Chi Xilun, Horita Masahiro, Suda Jun, Kimoto Tsunenobu

APPLIED PHYSICS EXPRESS Vol. 11 ( 9 ) 2018.9

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

Kazutaka Kanegae, Masahiro Horita, Tsunenobu Kimoto, Jun Suda

Applied Physics Express Vol. 11 ( 7 ) 2018.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Applied Physics

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 Kazutaka, Kaneko Mitsuaki, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 7 ) 2018.7

Language：English Publishing type：Research paper (scientific journal)

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

Takuya Maeda, Tetsuo Narita, Masakazu Kanechika, Tsutomu Uesugi, Tetsu Kachi, Tsunenobu Kimoto, Masahiro Horita, Jun Suda

Applied Physics Letters Vol. 112 ( 25 ) 2018.6

Language：English Publishing type：Research paper (scientific journal) Publisher：American Institute of Physics Inc.

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

Naoki Sawada, Tetsuo Narita, Masakazu Kanechika, Tsutomu Uesugi, Tetsu Kachi, Masahiro Horita, Tsunenobu Kimoto, Jun Suda

Applied Physics Express Vol. 11 ( 4 ) 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Applied Physics

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 Reviewed

2018 IEEE International Electron Devices Meeting (IEDM) 2018

Characterization of lightly-doped n- and p-type homoepitaxial GaN on free-standing substrates Invited Reviewed

Horita M., Suda J.

IMFEDK 2017 - 2017 International Meeting for Future of Electron Devices, Kansai page： 86 - 87 2017.7

Language：English Publisher：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 Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 5 ) 2017.5

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The formation of perhydropolysilazane (PHPS)-based SiO2 films by CO2 laser annealing is proposed. Irradiation with a CO2 laser with optimum fluence transformed a prebaked PHPS film into a SiO2 film with uniform composition in the thickness direction. Polycrystalline silicon thin-film transistors (poly-Si TFTs) with a SiO2 film as the gate insulator were fabricated. When the SiO2 film was formed by CO2 laser annealing (CO(2)LA) at the optimum fluence of 20mJ/cm(2), the film had fewer OH groups which was one-twentieth that of the furnace annealed PHPS film and one-hundredth that of the SiO2 film deposited by plasma-enhanced chemical vapor deposition (PECVD) using tetraethyl orthosilicate (TEOS). The resulting TFTs using PHPS showed a clear transistor operation with a field-effect mobility of 37.9 +/- 1.2 cm(2)V(-1)s(-1), a threshold voltage of 9.8 +/- 0.2 V, and a subthreshold swing of 0.76 +/- 0.02 V/decade. The characteristics of such TFTs were as good as those of a poly-Si TFT with a SiO2 gate insulator prepared by PECVD using TEOS. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.056503

Temperature dependence of barrier height in Ni/n-GaN Schottky barrier diode Reviewed

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

APPLIED PHYSICS EXPRESS Vol. 10 ( 5 ) 2017.5

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The temperature dependence of barrier height in a Ni/n-GaN Schottky barrier diode fabricated on a GaN homoepitaxial layer was investigated by capacitance-voltage, current-voltage, and internal photoemission measurements in the range of 223-573 K. The barrier height obtained by these methods linearly decreased with increasing temperature. The temperature coefficient was -(1.7-2.3) x 10(-4) eV/K, which is about half of the temperature coefficient of the band gap reported previously. This indicates that the decrease in the barrier height may mainly reflect the shrinkage of the band gap (lowering of the conduction band edge) in GaN with increasing temperature. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/APEX.10.051002

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

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 3 ) 2017.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

Mg-doped p-type gallium nitride (GaN) layers with doping concentrations in the range from 6.5 x 10(16)cm(-3) (lightly doped) to 3.8 x 10(19)cm(-3) (heavily doped) were investigated by Hall-effect measurement for the analysis of hole concentration and mobility. p-GaN was homoepitaxially grown on a GaN free-standing substrate by metalorganic vapor-phase epitaxy. The threading dislocation density of p-GaN was 4 x 10(6)cm(-2) measured by cathodoluminescence mapping. Hall-effect measurements of p-GaN were carried out at a temperature in the range from 130 to 450 K. For the lightly doped p-GaN, the acceptor concentration of 7.0 x 10(16)cm(-3) and the donor concentration of 3.2 x 10(16)cm(-3) were obtained, where the compensation ratio was 46%. We also obtained the depth of the Mg acceptor level to be 220meV. The hole mobilities of 86, 31, 14cm(2)V(-1) 1 s(-1) 1 at 200, 300, 400 K, respectively, were observed in the lightly doped p-GaN. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.031001