Faculty Profiles - HONDA, Yoshio

Papers - HONDA, Yoshio

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Multiple electron beam generation from InGaN photocathode

Daiki Sato, Haruka Shikano, Atsushi Koizumi, Tomohiro Nishitani, Yoshio Honda, Hiroshi Amano

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Vol. 39 ( 6 ) 2021.12

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

In this study, we generated 25 multielectron beam (MEB) using an InGaN photocathode with a negative electron affinity state irradiating with 25 multilaser beam. The uniformity of the MEB and the total electron beam current were evaluated. A laser beam was split into 25 laser beams using a spatial light modulator. The coefficient of variation (CV) of laser power was 20%. The CV of quantum efficiency was 1.1%. The CV of electron beam current was 12%, and the total current was about 1.2 mu A. These results will enhance the development of the MEB-defect inspection using the InGaN photocathode.

DOI： 10.1116/6.0001272

Web of Science

Vertical GaN p+-n junction diode with ideal avalanche capability grown by halide vapor phase epitaxy Reviewed

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

Applied Physics Letters Vol. 119 ( 15 ) page： 152102 - 152102 2021.10

Effective neutron detection using vertical-type BGaN diodes Reviewed

Takayuki Nakano, Ken Mochizuki, Takuya Arikawa, Hisaya Nakagawa, Shigeyoshi Usami, Yoshio Honda, Hiroshi Amano, Adrian Vogt, Sebastian Schütt, Michael Fiederle, Kazunobu Kojima, Shigefusa F. Chichibu, Yoku Inoue, Toru Aoki

Journal of Applied Physics Vol. 130 ( 12 ) page： 124501-1 - 10 2021.9

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

In this study, vertical-type thick BGaN PIN diodes were successfully fabricated to improve the neutron capture rate of BGaN diodes by improving the BGaN epitaxial growth technique. In this technique, 5-μm-thick epitaxial growth was achieved using trimethylboron as a B metal-organic source, which suppressed the gas-phase reaction. The α-particle energy spectrum, the neutron pulse signal, and the residual energy of particles emitted from a neutron capture reaction were measured using the fabricated BGaN diodes by performing radiation detection measurements. The detected signal position in the neutron detection signal spectrum was similar to that of 2.3 MeV α-particles. These results indicate that vertical-type BGaN diodes can be used as effective neutron detectors.

DOI： 10.1063/5.0051053

Web of Science

Scopus

Smart-cut-like laser slicing of GaN substrate using its own nitrogen

Atsushi Tanaka, Ryuji Sugiura, Daisuke Kawaguchi, Toshiki Yui, Yotaro Wani, Tomomi Aratani, Hirotaka Watanabe, Hadi Sena, Yoshio Honda, Yasunori Igasaki, Hiroshi Amano

Scientific Reports Vol. 11 ( 1 ) page： 17949 2021.9

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

We have investigated the possibility of applying lasers to slice GaN substrates. Using a sub-nanosecond laser with a wavelength of 532 nm, we succeeded in slicing GaN substrates. In the laser slicing method used in this study, there was almost no kerf loss, and the thickness of the layer damaged by laser slicing was about 40 µm. We demonstrated that a standard high quality homoepitaxial layer can be grown on the sliced surface after removing the damaged layer by polishing.

DOI： 10.1038/s41598-021-97159-w

Web of Science

Scopus

PubMed

Gallium nitride wafer slicing by a sub-nanosecond laser: effect of pulse energy and laser shot spacing

Hadi Sena, Atsushi Tanaka, Yotaro Wani, Tomomi Aratani, Toshiki Yui, Daisuke Kawaguchi, Ryuji Sugiura, Yoshio Honda, Yasunori Igasaki, Hiroshi Amano

Applied Physics A: Materials Science and Processing Vol. 127 ( 9 ) 2021.9

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

Gallium nitride (GaN)-based devices surpass the traditional silicon-based power devices in terms of higher breakdown voltage, faster-switching speed, higher thermal conductivity, and lower on-resistance. However, heteroepitaxial GaN growths like GaN on sapphire are not suitable for power devices due to the threading dislocation densities as high as 108/cm2. Recently, homoepitaxial GaN growth has become possible thanks to the native GaN substrates with dislocation densities in the order of 104/cm2 but the extremely high cost of the GaN substrates makes the homoepitaxy method unacceptable for industrial applications, and the slicing of wafers for reusing them is an effective solution for cost reduction. In this study, we will investigate a route for slicing the GaN single crystal substrate by controlling the laser pulse energy and changing the distance between each laser shot. The 2D and 3D crack propagations are observed by a multiphoton confocal microscope, and the cross section of samples is observed by a scanning electron microscope (SEM). The results showed that two types of radial and lateral cracking occurred depending on the pulse energy and shot pitch, and controlling them was of importance for attaining a smooth GaN substrate slicing. Cross-sectional SEM images showed that at suitable pulse energy and distance, crack propagation could be controlled with respect to the irradiation plane.

DOI： 10.1007/s00339-021-04808-y

Web of Science

Scopus

Reduction in operating voltage of AlGaN homojunction tunnel junction deep-UV light-emitting diodes by controlling impurity concentrations

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

Applied Physics Express Vol. 14 ( 8 ) 2021.8

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

We reduced the operating voltage of AlGaN homojunction tunnel junction (TJ) deep-ultraviolet (UV) light-emitting diodes (LEDs) by two approaches: the suppression of carbon incorporation and the doping of a high concentration of silicon in an n+-AlGaN layer. The AlGaN homojunction TJ deep-UV LEDs had a significantly reduced forward voltage upon suppressing the incorporation of carbon in the n+-AlGaN layer. The suppression of electron compensation by carbon in nitrogen sites and the doping of a high concentration of silicon in an n+-AlGaN layer are important for reducing the operating voltage of AlGaN homojunction TJ deep-UV LEDs.

DOI： 10.35848/1882-0786/ac0fb6

Web of Science

Scopus

Impact of gate electrode formation process on Al<inf>2</inf>O<inf>3</inf>/GaN interface properties and channel mobility

Yuto Ando, Manato Deki, Hirotaka Watanabe, Noriyuki Taoka, Atsushi Tanaka, Shugo Nitta, Yoshio Honda, Hisashi Yamada, Mitsuaki Shimizu, Tohru Nakamura, Hiroshi Amano

Applied Physics Express Vol. 14 ( 8 ) 2021.8

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

The interface properties of GaN metal-insulator-semiconductor (MIS) structures with a gate electrode metal deposited by electron beam (EB) or resistive heating evaporation were investigated. Also, the impact of the interface properties on the channel mobility in GaN MIS field-effect transistors was investigated. It was confirmed that interface charges including both interface states and positive fixed charges were introduced to an Al2O3/GaN interface by the formation of a gate electrode by EB evaporation. Consequently, the introduced interface charges degraded the electron mobility in the MIS channel.

DOI： 10.35848/1882-0786/ac0ffa

Web of Science

Scopus

Improving light output power of AlGaN-based deep-ultraviolet light-emitting diodes by optimizing the optical thickness of p-layers

Yusuke Matsukura, Tetsuhiko Inazu, Cyril Pernot, Naoki Shibata, Maki Kushimoto, Manato Deki, Yoshio Honda, Hiroshi Amano

Applied Physics Express Vol. 14 ( 8 ) page： 084004 - 084004 2021.8

Electrical properties and structural defects of p-type GaN layers grown by halide vapor phase epitaxy Reviewed

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

Journal of Crystal Growth Vol. 566 page： 126173 - 126173 2021.7

Vertical GaN-on-GaN nanowire Schottky barrier diodes by top-down fabrication approach

Yaqiang Liao, Tao Chen, Jia Wang, Yuto Ando, Wentao Cai, Xu Yang, Hirotaka Watanabe, Jun Hirotani, Atsushi Tanaka, Shugo Nitta, Yoshio Honda, Kevin J. Chen, Hiroshi Amano

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( 7 ) 2021.7

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

An optimized top-down approach was utilized to fabricate vertical GaN-on-GaN nanowire Schottky barrier diodes (NWSBDs) in this letter. The suppressed reverse leakage current and enhanced breakdown voltage (BV) of the vertical GaN NWSBDs are attributed to the reduced electric field at the interface of the Schottky junction achieved through the dielectric reduced surface field technique. As-fabricated NWSBD delivers a low turn-on voltage of 0.80 V, a near-unity ideality factor of 1.04, along with a soft BV of 480 V. The measured soft BV is comparable with the avalanche BV of the p-n diode with a similar net doping concentration in the drift region.

DOI： 10.35848/1347-4065/ac06b5

Web of Science

Etching-induced damage in heavily Mg-doped p-type GaN and its suppression by low-bias-power inductively coupled plasma-reactive ion etching

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

Japanese Journal of Applied Physics Vol. 60 ( SB ) 2021.5

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

Inductively coupled plasma–reactive ion etching (ICP–RIE)-induced damage in heavily Mg-doped p-type GaN ([Mg] = 2 × 1019 cm−3) was investigated by low-temperature photoluminescence (PL) and depth-resolved cathodoluminescence (CL) spectroscopy. From PL measurements, we found broad yellow luminescence (YL) with a maximum at around 2.2–2.3 eV, whose origin was considered to be isolated nitrogen vacancies (VN), only in etched samples. The depth-resolved CL spectroscopy revealed that the etching-induced YL was distributed up to the electron-beam penetration depth of around 200 nm at a high ICP–RIE bias power (Pbias). Low-bias-power (low-Pbias) ICP–RIE suppressed the YL and its depth distribution to levels similar to those of an unetched sample, and a current–voltage characteristic comparable to that of an unetched sample was obtained for a sample etched with Pbias of 2.5 W.

DOI： 10.35848/1347-4065/abd538

Web of Science

Scopus

Impact of heat treatment process on threshold current density in AlGaN-based deep-ultraviolet laser diodes on AlN substrate

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

Applied Physics Express Vol. 14 ( 5 ) page： 051003 - 051003 2021.5

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

Abstract

The electroluminescence (EL) uniformity of AlGaN-based deep UV laser diodes on AlN substrate was analyzed by using the EL imaging technique. Although nonuniform EL patterns were observed, the uniformity was improved by changing the position of the p-electrode. The threshold current density was also reduced by suppressing the inhomogeneity of the EL. Cathodoluminescence analysis revealed that the cause of the non-uniformity is the degradation of the active layer and the nonuniformity emission formed by rapid thermal annealing at high temperature after mesa structure formation.

DOI： 10.35848/1882-0786/abf443

Web of Science

Other Link： https://iopscience.iop.org/article/10.35848/1882-0786/abf443/pdf

Discrete AlN mole fraction of n/12 (n = 4–8) in Ga-rich zones functioning as electron pathways created in nonflat AlGaN layers grown on high-miscut sapphire substrates

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

Journal of Applied Physics Vol. 129 ( 16 ) page： 164503 - 164503 2021.4

Experimental demonstration of GaN IMPATT diode at X-band

Seiya Kawasaki, Yuto Ando, Manato Deki, Hirotaka Watanabe, Atsushi Tanaka, Shugo Nitta, Yoshio Honda, Manabu Arai, Hiroshi Amano

Applied Physics Express Vol. 14 ( 4 ) 2021.4

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

We report the first experimental demonstration of microwave oscillation in GaN impact ionization avalanche time transit (IMPATT) diodes at the X-band. The device used in this study is a single drift diode with a p+–n simple abrupt junction and vertical mesa termination. The reverse I–V characteristic of the diode shows low leakage current, clear avalanche breakdown, and high avalanche capability, as required for IMPATT operation. Microwave testing is performed in an X-band waveguide circuit with a reduced-height waveguide resonant cavity. Oscillations are observed at 9.52 GHz at a power of ∼56 mW.

DOI： 10.35848/1882-0786/abe3dc

Web of Science

Scopus

Numerical Simulation of Ammonothermal Crystal Growth of GaN—Current State, Challenges, and Prospects

Saskia Schimmel, Daisuke Tomida, Tohru Ishiguro, Yoshio Honda, Shigefusa Chichibu, Hiroshi Amano

Crystals Vol. 11 ( 4 ) page： 356 - 356 2021.4

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

Numerical simulations are a valuable tool for the design and optimization of crystal growth processes because experimental investigations are expensive and access to internal parameters is limited. These technical limitations are particularly large for ammonothermal growth of bulk GaN, an important semiconductor material. This review presents an overview of the literature on simulations targeting ammonothermal growth of GaN. Approaches for validation are also reviewed, and an overview of available methods and data is given. Fluid flow is likely in the transitional range between laminar and turbulent; however, the time-averaged flow patterns likely tend to be stable. Thermal boundary conditions both in experimental and numerical research deserve more detailed evaluation, especially when designing numerical or physical models of the ammonothermal growth system. A key source of uncertainty for calculations is fluid properties under the specific conditions. This originates from their importance not only in numerical simulations but also in designing similar physical model systems and in guiding the selection of the flow model. Due to the various sources of uncertainty, a closer integration of numerical modeling, physical modeling, and the use of measurements under ammonothermal process conditions appear to be necessary for developing numerical models of defined accuracy.

DOI： 10.3390/cryst11040356

Web of Science

Fabrication of GaN cantilever on GaN substrate by photo-electrochemical etching

Takehiro Yamada, Yuto Ando, Hirotaka Watanabe, Yuta Furusawa, Atsushi Tanaka, Manato Deki, Shugo Nitta, Yoshio Honda, Jun Suda, Hiroshi Amano

Applied Physics Express Vol. 14 ( 3 ) 2021.3

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

Photo-electrochemical (PEC) etching is a promising technique for fabricating GaN microelectromechanical systems devices. In this study, we demonstrate the fabrication of GaN cantilevers by the bandgap-selective PEC etching of an InGaN superlattice sacrificial layer. By using an InGaN superlattice as a sacrifice layer, we found the PEC etching rate became higher than using a normal InGaN layer. As a result, the InGaN superlattice was completely etched and we fabricated GaN-based cantilevers whose resonance characteristics were measured. The Young’s modulus of GaN was determined from the resonance characteristics of GaN cantilevers to be the same as the highest value reported previously.

DOI： 10.35848/1882-0786/abe657

Web of Science

Scopus

Boundary Conditions for Simulations of Fluid Flow and Temperature Field during Ammonothermal Crystal Growth—A Machine-Learning Assisted Study of Autoclave Wall Temperature Distribution Reviewed

Saskia Schimmel, Daisuke Tomida, Makoto Saito, Quanxi Bao, Toru Ishiguro, Yoshio Honda, Shigefusa Chichibu, Hiroshi Amano

Crystals Vol. 11 ( 3 ) page： 254 -1 - 27 2021.3

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

Thermal boundary conditions for numerical simulations of ammonothermal GaN crystal growth are investigated. A global heat transfer model that includes the furnace and its surroundings is presented, in which fluid flow and thermal field are treated as conjugate in order to fully account for convective heat transfer. The effects of laminar and turbulent flow are analyzed, as well as those of typically simultaneously present solids inside the autoclave (nutrient, baffle, and multiple seeds). This model uses heater powers as a boundary condition. Machine learning is applied to efficiently determine the power boundary conditions needed to obtain set temperatures at specified locations. Typical thermal losses are analyzed regarding their effects on the temperature distribution inside the autoclave and within the autoclave walls. This is of relevance because autoclave wall temperatures are a convenient choice for setting boundary conditions for simulations of reduced domain size. Based on the determined outer wall temperature distribution, a simplified model containing only the autoclave is also presented. The results are compared to those observed using heater-long fixed temperatures as boundary condition. Significant deviations are found especially in the upper zone of the autoclave due to the important role of heat losses through the autoclave head.

DOI： 10.3390/cryst11030254

Web of Science

Development of pulsed TEM equipped with nitride semiconductor photocathode for high-speed observation and material nanofabrication Reviewed

Hidehiro Yasuda, Tomohiro Nishitani, Shuhei Ichikawa, Shuhei Hatanaka, Yoshio Honda, Hiroshi Amano

Quantum Beam Science Vol. 5 ( 1 ) page： 5 - 5 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：{MDPI} {AG}

The development of pulsed electron sources is applied to electron microscopes or electron beam lithography and is effective in expanding the functions of such devices. The laser photocathode can generate short pulsed electrons with high emittance, and the emittance can be increased by changing the cathode substrate from a metal to compound semiconductor. Among the substrates, nitride-based semiconductors with a negative electron affinity (NEA) have good advantages in terms of vacuum environment and cathode lifetime. In the present study, we report the development of a photocathode electron gun that utilizes photoelectron emission from a NEA-InGaN substrate by pulsed laser excitation, and the purpose is to apply it to material nanofabrication and high-speed observation using a pulsed transmission electron microscope (TEM) equipped with it.

DOI： 10.3390/qubs5010005

Web of Science

Scopus

Suppression of the regrowth interface leakage current in AlGaN/GaN HEMTs by unactivated Mg doped GaN layer

T. Liu, H. Watanabe, S. Nitta, J. Wang, G. Yu, Y. Ando, Y. Honda, H. Amano, A. Tanaka, Y. Koide

Applied Physics Letters Vol. 118 ( 7 ) 2021.2

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

The leakage current caused by the Si pileup at the regrowth interface of AlGaN/GaN high electron mobility transistors (HEMTs) is significantly suppressed by the semi-insulating Mg-doped GaN layer. Mg is unintentionally doped and can be originated from the graphite susceptor of metal organic vapor phase epitaxy. Before regrowth of the AlGaN/GaN heterostructure, the GaN template is treated with hydrochloric acid (HCl) and hydrogen peroxide/potassium hydroxide (H2O2/KOH) solution to promote the adsorption of Mg on the GaN surface. The Mg-doped GaN channel layer is highly resistive due to the passivation of hydrogen. The p-n junction formed by the weakly p-type Mg-doped GaN layer and the n-type Si pileup layer depletes the excess electrons at the regrowth interface. As a result, the off-state drain leakage current of the HEMT device can be decreased by two orders of magnitude at 40 V.

DOI： 10.1063/5.0034584

Scopus

Optical properties of neodymium ions in nanoscale regions of gallium nitride: erratum

Shin-Ichiro Sato, Manato Deki, Hirotaka Watanabe, Shugo Nitta, Yoshio Honda, Tomoaki Nishimura, Brant C. Gibson, Andrew D. Greentree, Hiroshi Amano, Takeshi Ohshima

Optical Materials Express Vol. 11 ( 2 ) page： 524 - 524 2021.2

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Papers - HONDA, Yoshio