Faculty Profiles - HONDA, Yoshio

Papers - HONDA, Yoshio

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Temperature field, flow field and temporal fluctuations thereof in ammonothermal growth of bulk GaN - transition from dissolution stage to growth stage conditions Reviewed

S. Schimmel, D. Tomida, T. Ishiguro, Y. Honda, S. F. Chichibu, H. Amano

Materials Vol. 16 ( 5 ) page： 2016 1 - 27 2023.3

Red emission from InGaN active layer grown on nanoscale InGaN pseudosubstrates

Wentao Cai, Jia Wang, Jeong-Hwan Park, Yuta Furusawa, Heajeong Cheong, Shugo Nitta, Yoshio Honda, Markus Pristovsek, Hiroshi Amano

Japanese Journal of Applied Physics Vol. 62 ( 2 ) page： 020902 - 020902 2023.2

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

Abstract

We demonstrated nanoplatelet In x Ga1−x N pseudosubstrates with In content varying from 0 to 0.3 on low-dislocation-density GaN substrates. These nanoplatelets efficiently relax in-plane strain, thus allowing for the use of a thick active layer to reduce built-in polarization. The 15 nm thick InGaN active layers grown under the same conditions on these nanoplatelets showed a remarkable cathodoluminescence redshift from 460 to 617 nm, suggesting enhanced In incorporation efficiency in InGaN nanoplatelets with higher In content. Moreover, the 617 nm-emitting sample presented an imperceptible blueshift under excitation-power-dependent photoluminescence, indicating a weak polarization field introduced by the high-In-content pseudosubstrates and the thick active layer.

DOI： 10.35848/1347-4065/acb74c

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/acb74c/pdf

Scanning electron microscope imaging by selective e-beaming using photoelectron beams from semiconductor photocathodes

Tomohiro Nishitani, Yuta Arakawa, Shotaro Noda, Atsushi Koizumi, Daiki Sato, Haruka Shikano, Hokuto Iijima, Yoshio Honda, Hiroshi Amano

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Vol. 40 ( 6 ) 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：A V S AMER INST PHYSICS

Pulsed electron beams from a photocathode using an InGaN semiconductor have brought selectively scanning technology to scanning electron microscopes, where the electron beam irradiation intensity and area can be arbitrarily selected within the field of view in SEM images. The p-type InGaN semiconductor crystals grown in the metalorganic chemical vapor deposition equipment were used as the photocathode material for the electron beam source after the surface was activated to a negative electron affinity state in the electron gun under ultrahigh vacuum. The InGaN semiconductor photocathode produced a pulsed electron beam with a rise and fall time of 3 ns, consistent with the time structure of the irradiated pulsed laser used for the optical excitation of electrons. The InGaN photocathode-based electron gun achieved a total beam operation time of 1300 h at 15 mu A beam current with a downtime rate of 4% and a current stability of 0.033% after 23 cycles of surface activation and continuous beam operation. The InGaN photocathode-based electron gun has been installed in the conventional scanning electron microscope by replacing the original field emission gun. SEM imaging was performed by selective electron beaming, in which the scanning signal of the SEM system was synchronized with the laser for photocathode excitation to irradiate arbitrary regions in the SEM image at arbitrary intensity. The accuracy of the selection of regions in the SEM image by the selective electron beam was pixel by pixel at the TV scan speed (80 ns/pix, 25 frame/s) of the SEM.

DOI： 10.1116/6.0002111

Web of Science

High In content nitride sub-micrometer platelet arrays for long wavelength optical applications

Wentao Cai, Yuta Furusawa, Jia Wang, Jeong-Hwan Park, Yaqiang Liao, Hea-Jeong Cheong, Shugo Nitta, Yoshio Honda, Markus Pristovsek, Hiroshi Amano

Applied Physics Letters Vol. 121 ( 21 ) 2022.11

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

We demonstrate high, up to 30% In content InGaN sub-micrometer platelets on GaN by metalorganic vapor phase epitaxy. These InGaN platelets were selectively grown on flat GaN seeds formed in sub-micrometer-scale openings in a SiNx mask. The platelets were highly uniform without any dislocations or pits, with an atomically flat (0001) surface. The typical height was ∼120 nm, which significantly exceeded the normal critical layer thickness of a c-plane InGaN film. The strain state was comprehensively characterized by microbeam x-ray diffraction and transmission electron microscopy. Due to a gradual elastic relaxation of strain, the In content increased almost linearly from bottom to top because of the strong strain-dependent In incorporation. These platelets can serve as high-quality strain-relaxed templates for long wavelength micro-light-emitting diodes.

DOI： 10.1063/5.0120723

Web of Science

Substitutional diffusion of Mg into GaN from GaN/Mg mixture

Yuta Itoh, Shun Lu, Hirotaka Watanabe, Manato Deki, Shugo Nitta, Yoshio Honda, Atsushi Tanaka, Hiroshi Amano

Applied Physics Express Vol. 15 ( 11 ) page： 116505 - 116505 2022.11

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

Abstract

We evaluated Mg-diffusion into GaN from GaN/Mg mixture. The diffusion depth of Mg increased with diffusion temperature from 1100 °C to 1300 °C, whereas the Mg concentration remained constant at 2–3 × 1018 cm−3 independent of temperature. The estimated activation energy for Mg diffusion was 2.8 eV, from which the substitutional diffusion mechanism was predicted. Mg-diffused GaN samples showed p-type conductivity with a maximum hole mobility of 27.7 cm2 V−1 s−1, suggesting that substitutional diffusion contributes to Mg activation. This diffusion technique can be used to easily form p-type GaN and has potential as a p-type selective doping technique.

DOI： 10.35848/1882-0786/ac9c83

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1882-0786/ac9c83/pdf

The photoemission characteristics of a NEA InGaN photocathode by simultaneously supplying Cs and O2

Masahiro Kashima, Yuya Itokawa, Toshiya Kanai, Daiki Sato, Atsushi Koizumi, Hokuto Iijima, Tomohiro Nishitani, Yoshio Honda, Hiroshi Amano, Takashi Meguro

APPLIED SURFACE SCIENCE Vol. 599 2022.10

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

A high quantum efficiency (QE) can be obtained on negative electron affinity (NEA) surfaces. It is well-known that NEA surfaces can be formed on semiconductor materials such as GaAs by the alternating supply of cesium (Cs) and oxygen (O2), which is called the yo-yo method. While GaN and related compounds such as InGaN are expected to realize an NEA photocathode with a long lifetime, the surface reactions between GaAs and nitride semiconductors are completely different with respect to the increasing rate of QE induced by the supply of O2. In addition, the surface processes of photoemission from NEA nitride semiconductors have not yet been elucidated. In the present study, a higher QE was achieved in InGaN by simultaneously supplying Cs and O2 instead of using the conventional yo-yo method. The possible Cs adsorption states in relation to the photoemission are also discussed based on the QE tendencies and the temperature programmed desorption (TPD) spectra of the NEA surfaces formed under elevated temperature conditions. This study suggests that the Cs oxide species, which is one of the key compounds for imparting the NEA nature, decomposes at approximately 350 degrees C and that the InGaN-Cs2O2 structure is a possible candidate for NEA photocathodes.

DOI： 10.1016/j.apsusc.2022.153882

Web of Science

Tuning the p-type doping of GaN over three orders of magnitude via efficient Mg doping during halide vapor phase epitaxy Reviewed

Kazuki Ohnishi, Naoki Fujimoto, Shugo Nitta, Hirotaka Watanabe, Shun Lu, Manato Deki, Yoshio Honda, Hiroshi Amano

Journal of Applied Physics Vol. 132 ( 14 ) 2022.10

High-energy computed tomography as a prospective tool for in situ monitoring of mass transfer processes inside high-pressure reactors - a case study on ammonothermal bulk crystal growth of nitrides including GaN Reviewed

S. Schimmel, M. Salamon, D. Tomida, S. Neumeier, T. Ishiguro, Y. Honda, S. F, Chichibu, H. Amano

Materials 15 (17) Vol. 15 ( 17 ) page： 6165 1 - 17 2022.9

Surface kinetics in halide vapor phase epitaxial growth of GaN layers on GaN (0001) freestanding substrates Reviewed

Kazuki Ohnishi, Naoki Fujimoto, Shugo Nitta, Hirotaka Watanabe, Yoshio Honda, Hiroshi Amano

Journal of Crystal Growth Vol. 592 page： 126749 - 126749 2022.8

Weak metastability of AlxGa1−xN (x = 13/24, 15/24, 17/24) shown by analyzing AlGaN grown on AlN with dense macrosteps Reviewed International journal

Akira Hirano, Yosuke Nagasawa, Masamichi Ippommatsu, Hideki Sako, Ai Hashimoto, Ryuichi Sugie, Yoshio Honda, Hiroshi Amano, Kazunobu Kojima, Shigefusa F. Chichibu

Applied Physics Express Vol. 15 ( 7 ) page： 075505 1 - 5 2022.7

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

Abstract

Energy-dispersive X-ray signals calibrated by Rutherford backscattering indicated the generation of Al13/24Ga11/24N in Ga-rich stripes in a nonflat Al0.58Ga0.42N layer. Also, the CL peak wavelengths of ∼259 and 272 nm also showed the generation of Al15/24Ga9/24N and Al13/24Ga11/24N in Al-rich zones and Ga-rich stripes, respectively. The wavelength of a strong CL peak at ∼246 nm, which was observed from the Al0.7Ga0.3N layer in our previous study, is also considered to correspond to the near-band-emission wavelengths of Al17/24Ga7/24N. In particular, the stronger reproducibility of metastable Al15/24Ga9/24N generation was confirmed, in agreement with the computed predictions by other research groups.

DOI： 10.35848/1882-0786/ac79a1

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1882-0786/ac79a1/pdf

Space–Charge Profiles and Carrier Transport Properties in Dopant‐Free GaN‐Based p‐n Junction Formed by Distributed Polarization Doping

Takeru Kumabe, Seiya Kawasaki, Hirotaka Watanabe, Shugo Nitta, Yoshio Honda, Hiroshi Amano

physica status solidi (RRL) – Rapid Research Letters Vol. 16 ( 7 ) 2022.7

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

Herein, the operation of dopant‐free GaN‐based p‐n junctions formed by distributed polarization doping (DPD) is experimentally demonstrated and their space charge profiles and carrier transport properties are investigated. The device exhibits ideal space charge profiles explained by polarization effects and demonstrates the excellent controllability of DPD. In addition, it shows rectification and electroluminescence under forward‐biased conditions. The carrier transport properties could be explained by the conventional recombination/diffusion model used for impurity‐doped p‐n junctions. Repeatable breakdowns are also observed in all devices and the temperature‐dependent breakdown voltages reveal that the breakdowns are caused by avalanche multiplication, which is also the same as those reported in impurity‐doped GaN p‐n diodes. These results indicate that DPD is a promising doping technology for GaN‐based power devices overcoming any issues associated with conventional impurity doping.

DOI： 10.1002/pssr.202200127

Web of Science

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/pssr.202200127

Dual-peak electroluminescence spectra generated from Aln/12Ga1-n/12N (n=2, 3, 4) for AlGaN-based LEDs with nonflat quantum wells Reviewed

Y. Nagasawa, K. Kojima, A. Hirano, M. Ippommatsu, Y. Honda, H. Amano, S. F. Chichibu

Journal of Physics D: Applied Physics Vol. 55 ( 25 ) page： 255102 1 - 11 2022.6

“Regrowth-free” fabrication of high-current-gain AlGaN/GaN heterojunction bipolar transistor with N-p-n configuration

Takeru Kumabe, Hirotaka Watanabe, Yuto Ando, Atsushi Tanaka, Shugo Nitta, Yoshio Honda, Hiroshi Amano

Applied Physics Express Vol. 15 ( 4 ) page： 046506 - 046506 2022.4

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

Abstract

An AlGaN/GaN heterojunction bipolar transistor (HBT) with N-p-n configuration was fabricated by the “regrowth-free” method, resulting in a contamination-free emitter-base AlGaN/GaN heterojunction. The low-bias-power-based low-damage inductively coupled plasma–reactive ion etching was employed in this study for emitter mesa definition instead of the conventional selective-area-regrowth technique. The method successfully minimized the etching-induced damage in the p-GaN base layer and the contamination at the emitter-base AlGaN/GaN heterojunction. Consequently, the fabricated device exhibited a high current gain of 25, the highest current density of 15.0 kA cm−2, and the lowest on-state voltage offset of 0.75 V ever reported for AlGaN/GaN HBTs.

DOI： 10.35848/1882-0786/ac6197

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1882-0786/ac6197/pdf

Sputtered polycrystalline MgZnO/Al reflective electrodes for enhanced light emission in AlGaN-based homojunction tunnel junction DUV-LED

Taichi Matsubara, Kengo Nagata, Maki Kushimoto, Shigekazu Tomai, Satoshi Katsumata, Yoshio Honda, Hiroshi Amano

Applied Physics Express Vol. 15 ( 4 ) 2022.4

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

In this study, we enhanced the emission power of AlGaN-based tunnel junction deep-ultraviolet LEDs (TJ LEDs) by using a MgZnO and aluminum stacked structure as UV reflective electrodes on the anode side. The emission wavelength of the fabricated TJ LED was 284 nm, and the emission power was 57.3 mW at 63 A cm-2. The polycrystalline MgZnO enabled both conductivity and UV transmittance to be achieved, approximately doubling with a reflectance of the fabricated TJ LED at 284 nm compared to conventional TJ LED with Ti/Al. These factors contributed to the increased emission power of TJ LEDs.

DOI： 10.35848/1882-0786/ac5acf

Web of Science

Scopus

Structural design optimization of 279 nm wavelength AlGaN homojunction tunnel junction deep-UV light-emitting diode

Kengo Nagata, Satoshi Anada, Hiroshi Miwa, Shinichi Matsui, Shinya Boyama, Yoshiki Saito, Maki Kushimoto, Yoshio Honda, Tetsuya Takeuchi, Hiroshi Amano

Applied Physics Express Vol. 15 ( 4 ) page： 044003 - 044003 2022.4

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

Abstract

We demonstrated the structural optimization of AlGaN tunnel junction (TJ) deep-ultraviolet light-emitting diodes by changing the thickness and impurity concentrations of p+-type and n+-type AlGaN constituting the TJ. By decreasing the total thickness of the TJ to 23 nm, the operating voltage reached a minimum of 8.8 V at 63 A cm−2. Further decrease in TJ thickness markedly increases the operating voltage. This finding implies that the depletion layer width becomes greater than the TJ thickness if it is smaller than 12 nm. Therefore, we conclude that the TJ thickness must be greater than the depletion layer width.

DOI： 10.35848/1882-0786/ac60c7

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1882-0786/ac60c7/pdf

Visualization of depletion layer in AlGaN homojunction p–n junction

Kengo Nagata, Satoshi Anada, Yoshiki Saito, Maki Kushimoto, Yoshio Honda, Tetsuya Takeuchi, Kazuo Yamamoto, Tsukasa Hirayama, Hiroshi Amano

Applied Physics Express Vol. 15 ( 3 ) 2022.3

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

<title>Abstract</title>
We analyzed the p–n junction of an aluminum gallium nitride (AlGaN) homojunction tunnel junction (TJ) deep-ultraviolet light-emitting diode by phase-shifting electron holography. We clearly obtained a phase image reflecting the band alinement of the p–n homojunction and derived a depletion layer width of approximately 10 nm. In addition, the observed depletion layer width for the AlGaN TJ was in good agreement with the simulated one reflecting the diffusion profile of Mg and Si, thus enabling a discussion on the electrical conduction mechanism for an AlGaN p-n junction.

DOI： 10.35848/1882-0786/ac53e2

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1882-0786/ac53e2/pdf

Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN

Yuta Itoh, Hirotaka Watanabe, Yuto Ando, Emi Kano, Manato Deki, Shugo Nitta, Yoshio Honda, Atsushi Tanaka, Nobuyuki Ikarashi, Hiroshi Amano

Applied Physics Express Vol. 15 ( 2 ) 2022.2

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

We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100 °C with two beam currents. Photoluminescence spectra suggest that low-beam-current implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the density of intrinsic dislocation loops, suggesting decreases in the densities of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

DOI： 10.35848/1882-0786/ac481b

Web of Science

Scopus

Threshold increase and lasing inhibition due to hexagonal-pyramid-shaped hillocks in AlGaN-based DUV laser diodes on single-crystal AlN substrate

Maki Kushimoto, Ziyi Zhang, Yoshio Honda, Leo J. Schowalter, Chiaki Sasaoka, Hiroshi Amano

Japanese Journal of Applied Physics Vol. 61 ( 1 ) page： 010601 - 010601 2022.1

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

Abstract

The presence of hexagonal-pyramid-shaped hillocks (HPHs) in AlGaN epitaxial films affects device characteristics; this effect is significant in DUV laser diodes (LDs) on AlN substrates, where the presence of HPHs under the p-electrode increases the threshold current density and inhibits the lasing. In this study, we investigated the difference between the lasing characteristics of LDs with and without HPHs. It was found that in the presence of HPHs, the threshold excitation power density increased and the slope efficiency decreased by optical excitation. To investigate the cause of these phenomena, we performed structural, optical, and electrical analyses of the HPHs. Various imaging techniques were used to directly capture the characteristics of the HPHs. As a result, we concluded that HPHs cause the degradation of LD characteristics due to a combination of structural, optical, and electrical factors.

DOI： 10.35848/1347-4065/ac3a1d

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/ac3a1d/pdf

Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg Reviewed

Shun Lu, Manato Deki, Jia Wang, Kazuki Ohnishi, Yuto Ando, Takeru Kumabe, Hirotaka Watanabe, Shugo Nitta, Yoshio Honda, Hiroshi Amano

Applied Physics Letters Vol. 119 ( 24 ) page： 242104 - 242104 2021.12

Discrete wavelengths observed in electroluminescence originating from Al1/2Ga1/2N and Al1/3Ga2/3N created in nonflat AlGaN quantum wells Reviewed

Yosuke Nagasawa, Kazunobu Kojima, Akira Hirano, Hideki Sako, Ai Hashimoto, Ryuichi Sugie, Masamichi Ippommatsu, Yoshio Honda, Hiroshi Amano, Shigefusa F Chichibu

Journal of Physics D: Applied Physics Vol. 54 ( 48 ) page： 485107-1 - 10 2021.12

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Papers - HONDA, Yoshio