Faculty Profiles - HORITA Masahiro

Papers - HORITA Masahiro

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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

Web of Science

Scopus

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

Web of Science

Scopus

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

Web of Science

Scopus

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

Web of Science

Scopus

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

Web of Science

Scopus

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

Scopus

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

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

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

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Papers - HORITA Masahiro