Faculty Profiles - AMANO, Hiroshi

Papers - AMANO, Hiroshi

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

Nagata K., Makino H., Miwa H., Matsui S., Boyama S., Saito Y., Kushimoto M., Honda Y., Takeuchi T., Amano H.

Applied Physics Express Vol. 14 ( 8 ) 2021.8

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

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

Open Access

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

Ando Y., Deki M., Watanabe H., Taoka N., Tanaka A., Nitta S., Honda Y., Yamada H., Shimizu M., Nakamura T., Amano H.

Applied Physics Express Vol. 14 ( 8 ) 2021.8

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

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

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

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

JOURNAL OF CRYSTAL GROWTH Vol. 566 2021.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Crystal Growth

The electrical properties and structural defects of p-type GaN layers with Mg concentrations from 8.0 × 1018 to 8.3 × 1019 cm−3 grown by halide vapor phase epitaxy (HVPE) were investigated. In all samples, p-type conduction was confirmed at room temperature. The hole concentration at room temperature decreased in a heavily Mg-doped sample. By analyzing the results of Hall-effect measurements at various temperatures, the acceptor concentration decreased in a heavily Mg-doped sample, whereas the compensating donor concentration increased. These results affect the decrease in the hole concentration. The hole mobility decreased with increasing acceptor concentration. In the heavily Mg-doped sample, pyramidal inversion domains (PIDs) were formed. The size of each PID in an HVPE-grown sample is in good agreement with that Mg-doped GaN layers grown by metalorganic vapor phase epitaxy (MOVPE). Thus, the formation mechanism of PIDs in HVPE-grown samples is possibly the same as that in MOVPE-grown samples. Energy-dispersive X-ray spectroscopy shows that Mg atoms accumulate in PIDs, which suggests that Mg atoms in PIDs are electrically inactive, inhibiting the increase in the acceptor concentration. These results are useful guidelines for fabricating p-type GaN layers with higher hole concentrations by HVPE.

DOI： 10.1016/j.jcrysgro.2021.126173

Web of Science

Scopus

赤﨑勇先生のご逝去を悼む

天野浩

応用物理 Vol. 90 ( 7 ) page： 455 - 455 2021.7

赤﨑　勇先生を偲んで Open Access

天野浩

日本物理学会誌 Vol. 76 ( 7 ) page： 478 - 478 2021.7

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

Liao Y., Chen T., Wang J., Ando Y., Cai W., Yang X., Watanabe H., Hirotani J., Tanaka A., Nitta S., Honda Y., Chen K.J., Amano H.

Japanese Journal of Applied Physics Vol. 60 ( 7 ) 2021.7

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

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

Scopus

Isamu Akasaki: The Pioneer of Blue LEDs and his Collaboration with <i>pss</i> OBITUARY Open Access

Amano, H

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE Vol. 218 ( 14 ) 2021.7

Non-polar true-lateral GaN power diodes on foreign substrates Open Access

Wang, J; Yu, G; Zong, H; Liao, YQ; Lu, WF; Cai, WT; Hu, XD; Xie, YH; Amano, H

APPLIED PHYSICS LETTERS Vol. 118 ( 21 ) 2021.5

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

We have demonstrated non-polar GaN power diodes (Schottky barrier diode and p-n junction diode) on foreign substrates featuring the true-lateral p-n and metal-semiconductor junctions. The diodes were fabricated on GaN islands laterally overgrown on the mask-patterned sapphire and Si substrates by metalorganic vapor phase epitaxy. The anode and cathode were formed on the opposed a-plane sidewalls of the island, making the device architecture essentially like the 90° rotation of the desired true-vertical power diodes. The ideality factor of the Schottky barrier diode remained 1.0 (from 1.00 to 1.05) over 7 decades in current. Specifically, a high critical electric field of 3.3 MV/cm was demonstrated on the p-n junction diode with avalanche capability. These performances reveal a strong potential of non-polar GaN with the true-lateral junctions for high power applications.

DOI： 10.1063/5.0051552

Open Access

Web of Science

Scopus

The stability of graphene and boron nitride for III-nitride epitaxy and post-growth exfoliation. Open Access

Park JH, Yang X, Lee JY, Park MD, Bae SY, Pristovsek M, Amano H, Lee DS

Chemical science Vol. 12 ( 22 ) page： 7713 - 7719 2021.5

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

A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material. However, when graphene, a representative 2-D material, is present on substrates that have a nitrogen atom, graphene loss occurs. Although this phenomenon has remained a hurdle for over a decade, restricting the advantages of applying graphene in the growth of III-nitride materials, few previous studies have been conducted. Here, we report the stability of graphene on substrates containing oxygen or nitrogen atoms. Graphene has been observed on highly decomposed Al2O3; however, graphene loss occurred on decomposed AlN at temperatures over 1300 °C. To overcome graphene loss, we investigated 2-D hexagonal boron nitride (h-BN) as an alternative. Unlike graphene on AlN, it was confirmed that h-BN on AlN was intact after the same high-temperature process. Moreover, the overgrown AlN layers on both h-BN/AlN and h-BN/Al2O3could be successfully exfoliated, which indicates that 2-D h-BN survived after AlN growth and underlines its availability for the vdWE/RE of III-nitrides with further mechanical transfer. By enhancing the stability of the 2-D material on the substrate, our study provides insights into the realization of a novel epitaxy concept.

DOI： 10.1039/d1sc01642c

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

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( SB ) page： SBBD03 2021.5

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

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

APPLIED PHYSICS EXPRESS Vol. 14 ( 5 ) page： 051003 2021.5

Micro-Light Emitting Diode: From Chips to Applications

Parbrook Peter J., Corbett Brian, Han Jung, Seong Tae-Yeon, Amano Hiroshi

LASER & PHOTONICS REVIEWS Vol. 15 ( 5 ) page： 2000133 2021.5

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

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

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

Experimental demonstration of GaN IMPATT diode at X-band

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

APPLIED PHYSICS EXPRESS Vol. 14 ( 4 ) page： 046501 2021.4

Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes

Sim Kee-Baek, Kim Su-Kyung, Lee Hwa-Seub, Lee Sang-Youl, Seong Tae-Yeon, Amano Hiroshi

ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY Vol. 10 ( 4 ) page： 045005 2021.4

Numerical simulation of ammonothermal crystal growth of GaN-current state, challenges, and prospects Open Access

Crystals Vol. 11 ( 4 ) page： 356 2021.4

Strain-induced yellow to blue emission tailoring of axial InGaN/GaN quantum wells in GaN nanorods synthesized by nanoimprint lithography. Open Access

Avit G, Robin Y, Liao Y, Nan H, Pristovsek M, Amano H

Scientific reports Vol. 11 ( 1 ) page： 6754 2021.3

Progress in Modeling Compound Semiconductor Epitaxy: Unintentional Doping in GaN MOVPE

Kangawa Yoshihiro, Kusaba Akira, Kempisty Pawel, Shiraishi Kenji, Nitta Shugo, Amano Hiroshi

CRYSTAL GROWTH & DESIGN Vol. 21 ( 3 ) page： 1878 - 1890 2021.3

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

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

APPLIED PHYSICS EXPRESS Vol. 14 ( 3 ) page： 036505 2021.3

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

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

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

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Papers - AMANO, Hiroshi