Faculty Profiles - AMANO, Hiroshi

Papers - AMANO, Hiroshi

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The photoemission characteristic of InGaN in NEA activation under heating

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

JSAP Annual Meetings Extended Abstracts Vol. 2022.1 ( 0 ) page： 1343 - 1343 2022.2

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

Itoh, Y; Watanabe, H; Ando, Y; Kano, E; Deki, M; Nitta, S; Honda, Y; Tanaka, A; Ikarashi, N; Amano, H

APPLIED PHYSICS EXPRESS Vol. 15 ( 2 ) 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Express

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

Defect characterization of { 10 1 ¯ 3 } GaN by electron microscopy Reviewed

Kusch G., Frentrup M., Hu N., Amano H., Oliver R.A., Pristovsek M.

Journal of Applied Physics Vol. 131 ( 3 ) 2022.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Applied Physics

Advances in obtaining untwinned (10 1 ¯3)-oriented semi-polar GaN enable a new crystal orientation for the growth of green and red LED structures. We present a scanning electron microscopy study that combines the structural characterization of electron channeling contrast imaging with the optical characterization of cathodoluminescence hyperspectral imaging on a (10 1 ¯ 3) GaN layer. An extensive defect analysis revealed that the dominant defects consist of basal plane stacking faults (BSFs), prismatic stacking faults, partial dislocations, and threading dislocations. With a defect density of about an order of magnitude lower than in comparable. The optical properties of the defects have been characterized from 10 to 320 K, showing BSF luminescence at room temperature indicating a reduced density of non-radiative recombination centers in the as-grown samples compared to established semi- and non-polar orientations. Our findings suggest that growth along (10 1 ¯3) has the potential for higher radiative efficiency than established semi-polar orientations.

DOI： 10.1063/5.0077084

Perspective on thermal conductance across heterogeneously integrated interfaces for wide and ultrawide bandgap electronics Reviewed

Cheng, Z; Graham, S; Amano, H; Cahill, DG

APPLIED PHYSICS LETTERS Vol. 120 ( 3 ) 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

Heterogeneous integration is important to create multi-functionality in future electronic devices. However, few thermal studies of the interfaces formed in these integrated devices have been reported before. Recently, integrated interfaces by surface-Activated bonding were found to have high thermal boundary conductance, which provides a solution for heat dissipation of GaN and β-Ga2O3-based power electronics. Here, we review the recent progress on the interfacial thermal transport across heterogeneously integrated interfaces, including transferred van der Waals force bonded interfaces, surface-Activated bonded interfaces, plasma bonded interfaces, and hydrophilic bonded interfaces. This Perspective specifically focuses on applications of thermal management strategies of electronics, especially power electronics. Finally, the challenges, such as high-Throughput thermal measurements of buried interfaces, thermal property-structure relations of interfaces bonded under different conditions, theoretical understanding of interfacial thermal transport, and device demonstrations, are pointed out.

DOI： 10.1063/5.0077039

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

Kushimoto, M; Zhang, ZY; Honda, Y; Schowalter, LJ; Sasaoka, C; Amano, H

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( 1 ) 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

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

Ohmic Contact to <i>p</i>-Type GaN Enabled by Post-Growth Diffusion of Magnesium Reviewed

Wang, J; Lu, S; Cai, WT; Kumabe, T; Ando, Y; Liao, YQ; Honda, Y; Xie, YH; Amano, H

IEEE ELECTRON DEVICE LETTERS Vol. 43 ( 1 ) page： 150 - 153 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Electron Device Letters

We demonstrated the formation of excellent Ohmic contact to p-type GaN (including the plasma etching-damaged p-type GaN which otherwise exhibited undetectable current within ±5 V) by the post-growth diffusion of magnesium. The specific contact resistivity on the order of 10-4Omega cm2 (extracted at V=0 V) was achieved on the plasma-damaged p-GaN with linear current-voltage characteristics by the transfer length method (TLM) measurement. The improvement in current by a factor of over 109 was also obtained on the plasma-damaged p-n junction diode after the same Mg-treatment. These experimental results indicate a great potential of post-growth diffusion of Mg to overcome the bottleneck of forming a good Ohmic contact to p-GaN.

DOI： 10.1109/LED.2021.3131057

Frontier electronics in memory of Professor Isamu Akasaki Invited

Amano, H

GALLIUM NITRIDE MATERIALS AND DEVICES XVII Vol. 12001 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of SPIE - The International Society for Optical Engineering

ISAMU AKASAKI, crystal grower, a pioneer of GaN-based blue light-emitting diodes (LEDs), and a Nobel Laureate in Physics, passed away because of pneumonia on April 1, 2021 at the age of 92. According to the Nobel Foundation, the LED lamp holds considerable promise for improving the quality of life of over 1.5 billion people worldwide who lack access to electricity grids. Owing to its low power requirements, it can be powered by cheap local solar energy. In this article, his pursuit of blue LEDs for 20 years is described.

DOI： 10.1117/12.2619005

An Accurate Approach to Develop Small Signal Circuit Models for AlGaN/GaN HEMTs Using Rational Functions and Dependent Current Sources Reviewed

Jadhav, A; Ozawa, T; Baratov, A; Asubar, JT; Kuzuhara, M; Wakejima, A; Yamashita, S; Deki, M; Nitta, S; Honda, Y; Amano, H; Roy, S; Sarkar, B

IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY Vol. 10 page： 797 - 807 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Journal of the Electron Devices Society

In this paper, a technique to develop small signal circuit (SSC) models of AlGaN/GaN high electron mobility transistors (HEMTs) using dependent current sources is presented. In this technique, experimentally measured broadband Y-parameters of AlGaN/GaN HEMTs are mathematically modeled as a sum of pole-residue terms. By representing each pole-residue term as a dependent current source, it is possible to develop an accurate SSC models for HEMTs which otherwise may not be possible using passive resistive-inductive-capacitive elements. The accuracy of the proposed SSC model is validated against the conventional SSC model using a 2nd, 3rd and 4th order rational function representation of the admittance branches of AlGaN/GaN HEMTs. Therefore, the proposed SSC model turns out to be highly robust in nature and can take care of any form of the transfer functions of the admittance branches between the gate, drain, and source terminal of an AlGaN/GaN HEMT.

DOI： 10.1109/JEDS.2022.3208028

Promising Results of National Project by Japanese Ministry of the Environment to Develop GaN on GaN Power Devices and Prove their Usefulness in Real Systems

Otoki Y., Shibata M., Mishima T., Ohta H., Mori Y., Imanishi M., Tamura S., Kidera K., Takino J., Okayama Y., Watanabe K., Okamoto N., Honda Y., Yamamoto M., Shiozaki K., Amano H.

2022 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2022 page： 237 - 242 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：2022 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2022

Exciting high performance power electronic devices have been widely demonstrated and manufactured using GaN epitaxial layers, but the majority of these devices have been fabricated on lattice mismatched substrates, including SiC, Si, or sapphire. Unfortunately, using lattice mismatched substrates inevitably introduces high concentrations of point defects and dislocations into the GaN epilayers, and these defects degrade the electrical performance of the fabricated GaN devices. Also, the mismatch of lattice constant and coefficient of thermal expansion cause strain and wafer bowing in the GaN epi, which further degrade the quality material for device fabrication. Using lattice matched GaN substrates provides solutions to these problems. In 2014, the Ministry of the Environment launched a national project to develop the required technology and to prove the superiority of GaN on GaN devices in real systems, with more than 10 partnerships from academia and industry. The project included work in several areas, including GaN substrate growth, GaN epitaxy, material characterization, and fabrication of devices and ICs for application in various systems. Large area GaN substrates have been grown with low defect densities, which has enabled fabrication of new types of vertical and horizontal GaN devices. The GaN devices have been used in servers, solar cell power conditioners, microwave ICs, distribution transformers, electric vehicle power converters. The performance improvements were compared with conventional approaches in each case. An “ALL GaN vehicle” has also been demonstrated, in which GaN devices are used in all power components. In this talk, we will present these results which show the great potential of GaN on GaN devices in the industry.

Development of Desktop Air Curtain System to Block Aerosols in Exhaled Breath

TAKAMURE Kotaro, SAKAMOTO Yasuaki, YAGI Tetsuya, IWATANI Yasumasa, AMANO Hiroshi, UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2022 ( 0 ) page： S055-10 2022

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

<p>A desktop-type air curtain device capable of being installed on a desk to protect healthcare workers from infectious diseases was developed. Pseudo-exhaled air containing aerosol particles emitted from a mannequin was blown toward the air curtain generated by the air curtain device. The aerosol blocking effect of the air curtain device was investigated using particle image velocimetry measurements. Air curtain flow was maintained inside the gate of the air curtain device. The aerosol particles approaching the air curtain device were observed to abruptly bend towards the suction port without passing through the gate, signifying that the aerosol particles were blocked by the air curtain flow.</p>

DOI： 10.1299/jsmemecj.2022.s055-10

Collection and Inactivation Abilities of Virus Flowing in a Return Air Channel with a DUV- LED

TAKAMURE Kotaro, IWATANI Yasumasa, SAKAMOTO Yasuaki, YAGI Tetsuya, AMANO Hiroshi, UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2022 ( 0 ) page： S055-11 2022

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

<p>A virus inactivation unit that can inactivate viruses was developed using deep ultraviolet (DUV) LEDs that emit DUV rays with a wavelength of 280 nm. The flow characteristics of virus particles inside the virus inactivation unit were investigated using numerical simulations. The percentage of particles colliding on the inner wall of the virus inactivation unit is 56 %. Especially, many particles collide with the partition plates behind the sharp-turn parts.</p>

DOI： 10.1299/jsmemecj.2022.s055-11

Blocking and collecting effect of aerosol particles by desktop air curtain system

TAKAMURE Kotaro, KOBAYASHI Daisuke, MUTO Hiromasa, HARUKI Taketo, AMANO Hiroshi, YAGI Tetsuya, IWATANI Yasumasa, UCHIYAMA Tomomi

The Proceedings of the Fluids engineering conference Vol. 2022 ( 0 ) page： OS03-22 2022

Uniting a III-Nitride Transmitter, Waveguide, Modulator, and Receiver on a Single Chip Reviewed

Xie, MY; Jiang, Y; Gao, XM; Cai, W; Yuan, JL; Zhu, HB; Wang, YJ; Zeng, XF; Zhang, ZY; Liu, YH; Amano, H

ADVANCED ENGINEERING MATERIALS Vol. 23 ( 12 ) 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Advanced Engineering Materials

The integration of III-nitride electronics and photonics is of great interest toward future computing systems with low power consumption. Multifunctioning multiple quantum well (MQW) diodes can address the challenging issue for on-chip integration of a light source, which is a key component to drive the photonic circuits. Herein, a transmitter, waveguide, modulator, and receiver are monolithically integrated on a III-nitride-on-silicon platform to perform light emission, transmission, modulation, and detection simultaneously. Both the receiver and modulator exhibit sufficient sensitivity to optical signals from the transmitter, which has an identical InGaN/AlGaN multiple quantum well (MQW) structure because the III-nitride diode provides spectral overlap between the emission and absorption spectra. On-chip data communication among these optical components is achieved using light, and the effective wavelength range is from 365 to 385 nm, in which multifunctional devices can be operated.

DOI： 10.1002/adem.202100582

Discrete wavelengths observed in electroluminescence originating from Al<inf>1/2</inf>Ga<inf>1/2</inf>N and Al<inf>1/3</inf>Ga<inf>2/3</inf>N created in nonflat AlGaN quantum wells Reviewed

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

Journal of Physics D: Applied Physics Vol. 54 ( 48 ) 2021.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Physics D: Applied Physics

When nonflat Al x Ga1-x N quantum wells (QWs) for producing 285 nm light emitting diodes (LEDs) were fabricated on n-AlGaN on AlN templates with dense macrosteps on c(0001) sapphire substrates with a 1.0 miscut relative to the m[1-100] axis, composite electroluminescence (EL) spectra from both inclined and terrace zones in Al x Ga1-x N QWs (x∼ 1/3) were generated owing to compositional and thickness modulations. The shoulder or main peaks in composite EL spectra tended to locate at fixed discrete wavelengths of ∼287, ∼292, and ∼296 nm from 12 nonuniform 285 nm LED wafers that were involved in nonnegligible run-to-run drift, even though these wafers were fabricated using the same source gas flow parameters for metal-organic vapor phase epitaxy. The discrete wavelengths of ∼287, ∼292, and ∼296 nm were attributed to EL from Al1/3Ga2/3N QWs with thicknesses of 8, 9, and 10 monolayers (ML), respectively, by referring to the results of cathodoluminescence (CL) analysis. Also, when nonflat Al x Ga1-x N QWs (x∼ 1/2) for 265 nm LEDs were grown, single-peak-like EL spectra were mainly generated from the inclined zones in nonflat QWs. The EL spectra taken from four nonuniform 265 nm LED wafers tended to show weak structures or main peaks at ∼257, ∼261, ∼266, and ∼271 nm, which were also attributed to emissions from Al1/2Ga1/2N QWs with thicknesses of 5, 6, 7, and 8 ML, respectively, by referring to CL analysis results. The creation of Al1/3Ga2/3N and Al1/2Ga1/2N in nonflat QWs in this work was in agreement with the results of our previous studies that indicated the creation of metastable Al n/12Ga1-n/12N (n: consecutive natural numbers). Furthermore, QW thicknesses of consecutive n ML may imply that Al1/3Ga2/3N and Al1/2Ga1/2N have 1 ML configurations of Al and Ga atoms on a c(0001) plane.

DOI： 10.1088/1361-6463/ac2065

Multiple electron beam generation from InGaN photocathode Reviewed

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

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics

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 μA. These results will enhance the development of the MEB-defect inspection using the InGaN photocathode.

DOI： 10.1116/6.0001272

Modified Small Signal Circuit of AlGaN/GaN MOS-HEMTs Using Rational Functions Reviewed

Jadhav, A; Ozawa, T; Baratov, A; Asubar, JT; Kuzuhara, M; Wakejima, A; Yamashita, S; Deki, M; Nitta, S; Honda, Y; Amano, H; Roy, S; Sarkar, B

IEEE TRANSACTIONS ON ELECTRON DEVICES Vol. 68 ( 12 ) page： 6059 - 6064 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Electron Devices

Conventional lumped small signal circuit (SSC) models of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) are derived from the low frequency portion of the experimentally measured ${Y}$ -parameters. Consequently, these models cannot faithfully capture the high frequency behavior of the device. In this work, modified SSC models of AlGaN/GaN MOS-HEMTs are developed by fitting the entire broadband measured ${Y}$ -parameters of the device with rational functions. These rational functions are then physically realized using additional passive circuit elements added to the conventional SSC model. The accuracy of the proposed SSC models can be improved by increasing the order of the rational functions. The proposed models are demonstrably more accurate than the conventional SSC models in estimating the higher order poles and zeroes present in the experimentally measured ${Y}$ -parameters of AlGaN/GaN MOS-HEMTs.

DOI： 10.1109/TED.2021.3119528

Vertical GaN p<SUP>+</SUP>-n junction diode with ideal avalanche capability grown by halide vapor phase epitaxy (vol 119, 152102, 2021) Reviewed

Ohnishi, K; Kawasaki, S; Fujimoto, N; Nitta, S; Watanabe, H; Honda, Y; Amano, H

APPLIED PHYSICS LETTERS Vol. 119 ( 20 ) 2021.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

After the paper was published,1we found errors in the manuscript shown in page 152102-2. In the original published article, the SIMS detec-tion limits of [O] and [H] were written as 7 × 1015and 3 × 1015cm-3, respectively. The corrected detection limits of [O] and [H] are 6 × 1015and 3 × 1016cm-3, respectively. The SIMS depth profiles shown in Fig. 2(b) and the conclusions of the paper are not affected by this erratum.

DOI： 10.1063/5.0077364

OBITUARY Isamu Akasaki Reviewed

Amano, H

PHYSICS TODAY Vol. 74 ( 11 ) page： 63 - 63 2021.11

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

Ohnishi, K; Kawasaki, S; Fujimoto, N; Nitta, S; Watanabe, H; Honda, Y; Amano, H

APPLIED PHYSICS LETTERS Vol. 119 ( 15 ) 2021.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

A vertical GaN p+-n junction diode with an ideal breakdown voltage was grown by halide vapor phase epitaxy (HVPE). A steep p+-n interface was observed even with the use of the HVPE method. No Si-accumulating layer was formed at the p+-n interface because of the continuous HVPE growth from the n-type drift layer to the p-type layer. This method provides improved electrical properties compared with the regrowth of p-type GaN layers. The minimum ideality factor of approximately 1.6 was obtained. The breakdown voltage increased from 874 to 974 V with the increase in the temperature from 25 to 200 °C, which suggests that avalanche multiplication causes the breakdown. The temperature-dependent breakdown voltage was in good agreement with the breakdown voltage calculated using the ideal critical electric field. These results indicate that HVPE is promising for the fabrication of vertical GaN power devices.

DOI： 10.1063/5.0066139

Effective neutron detection using vertical-type BGaN diodes Reviewed

Nakano, T; Mochizuki, K; Arikawa, T; Nakagawa, H; Usami, S; Honda, Y; Amano, H; Vogt, A; Schuett, S; Fiederle, M; Kojima, K; Chichibu, SF; Inoue, Y; Aoki, T

JOURNAL OF APPLIED PHYSICS Vol. 130 ( 12 ) 2021.9

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

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

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