研究者詳細 - 天野　浩

論文 - 天野　浩

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Observation of 2D-magnesium-intercalated gallium nitride superlattices. 査読有り

Wang J, Cai W, Lu W, Lu S, Kano E, Agulto VC, Sarkar B, Watanabe H, Ikarashi N, Iwamoto T, Nakajima M, Honda Y, Amano H

Nature 631 巻 ( 8019 ) 頁： 67 - 72 2024年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nature

Since the demonstration of p-type gallium nitride (GaN) through doping with substitutional magnesium (Mg) atoms1,2, rapid and comprehensive developments, such as blue light-emitting diodes, have considerably shaped our modern lives and contributed to a more carbon-neutral society3–5. However, the details of the interplay between GaN and Mg have remained largely unknown6–11. Here we observe that Mg-intercalated GaN superlattices can form spontaneously by annealing a metallic Mg film on GaN at atmospheric pressure. To our knowledge, this marks the first instance of a two-dimensional metal intercalated into a bulk semiconductor, with each Mg monolayer being intricately inserted between several monolayers of hexagonal GaN. Characterized as an interstitial intercalation, this process induces substantial uniaxial compressive strain perpendicular to the interstitial layers. Consequently, the GaN layers in the Mg-intercalated GaN superlattices exhibit an exceptional elastic strain exceeding −10% (equivalent to a stress of more than 20 GPa), among the highest recorded for thin-film materials12. The strain alters the electronic band structure and greatly enhances hole transport along the compression direction. Furthermore, the Mg sheets induce a unique periodic transition in GaN polarity, generating polarization-field-induced net charges. These characteristics offer fresh insights into semiconductor doping and conductivity enhancement, as well as into elastic strain engineering of nanomaterials and metal–semiconductor superlattices13.

DOI： 10.1038/s41586-024-07513-x

15 GHz GaN Hi-Lo IMPATT Diodes With Pulsed Peak Power of 25.5 W 査読有り

Kawasaki, S; Kumabe, T; Deki, M; Watanabe, H; Tanaka, A; Honda, Y; Arai, M; Amano, H

IEEE TRANSACTIONS ON ELECTRON DEVICES 71 巻 ( 3 ) 頁： 1408 - 1415 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Transactions on Electron Devices

The p+-n-n - n+ structure, known as Hi-Lo structure, was investigated in gallium nitride (GaN) single-drift-region (SDR) impact ionization avalanche transit-time (IMPATT) diodes to improve the output power and efficiency. The 15 GHz GaN Hi-Lo IMPATT diode was designed according to the Scharfetter and Gummel model under realistic conditions, suppressing the tunneling current (<10-4 cm2) and breakdown voltage (< 400 V). Even in such conditions, the calculated efficiency was higher than that of the p+-n abrupt junction structure and the improvement of RF characteristics was expected. The fabricated GaN Hi-Lo IMPATT diodes showed a clear avalanche breakdown and a pulsed microwave oscillation in the frequency range from 15 to 17 GHz. The maximum peak output power of 25.5 W and the efficiency of 2% were achieved, showing the highest values on microwave band GaN IMPATT diodes, and we confirmed that the Hi-Lo structure is effective for the high-power and high-efficiency operation of GaN IMPATT diodes.

DOI： 10.1109/TED.2023.3345822

Demonstration of AlGaN-on-AlN p-n Diodes With Dopant-Free Distributed Polarization Doping 査読有り

Kumabe T., Yoshikawa A., Kawasaki S., Kushimoto M., Honda Y., Arai M., Suda J., Amano H.

IEEE Transactions on Electron Devices 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Transactions on Electron Devices

Nearly ideal vertical Al<inline-formula> <tex-math notation="LaTeX">$_{\textit{x}}$</tex-math> </inline-formula>Ga<inline-formula> <tex-math notation="LaTeX">$_{\text{1}-\textit{x}}$</tex-math> </inline-formula>N (<inline-formula> <tex-math notation="LaTeX">$\text{0.7} \leq \textit{x} < \text{1.0}$</tex-math> </inline-formula>) p-n diodes are fabricated on an aluminum nitride (AlN) substrate. Distributed polarization doping (DPD) was employed for both p-type and n-type layers of the p-n junction, instead of conventional impurity doping, to overcome the major bottleneck of AlN-based material: the control of conductivity. Capacitance–voltage measurements revealed that the net charge concentration agreed well with the DPD charge concentration expected from the device layer structure. The fabricated devices exhibited a low turn-on voltage of 6.5 V, a low differential specific ON-resistance of 3 M<inline-formula> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula>, electroluminescence (maximum at 5.1 eV), and an ideality factor of 2 for a wide range of temperatures (room temperature—573 K). Moreover, the breakdown electric field was 7.3 MV cm<inline-formula> <tex-math notation="LaTeX">$^{-\text{1}}$</tex-math> </inline-formula>, which was almost twice as high as the reported critical electric field of GaN at the same doping concentration. These results clearly demonstrate the usefulness of DPD in the fabrication of high-performance AlN-based power devices.

DOI： 10.1109/TED.2024.3367314

Junction Diameter Dependence of Oscillation Frequency of GaN IMPATT Diode Up to 21 GHz 査読有り

Kawasaki, S; Kumabe, T; Ando, Y; Deki, M; Watanabe, H; Tanaka, A; Honda, Y; Arai, M; Amano, H

IEEE ELECTRON DEVICE LETTERS 44 巻 ( 8 ) 頁： 1328 - 1331 2023年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Electron Device Letters

An experimental study on the effects of junction capacitance and current density on the oscillation characteristics of GaN single-drift-region (SDR) impact ionization avalanche transit-time (IMPATT) diodes were carried out using GaN p+-n abrupt junction diodes of various diameters, 200, 150, and 100 μ m , with a depletion layer width of 2 μ m. The fabricated diodes showed a clear avalanche breakdown at 315 V and a pulsed microwave oscillation with a peak output power exceeding 30 dBm. The oscillation frequency depended on junction diameter and current density. It was widely modulated from 8.56 to 21.1 GHz with decreasing junction diameter and increasing current density. The highest oscillation frequency was obtained with a current density of 13.8 kA/cm2 and a junction diameter of 100 μ m. A numerical calculation based on Read-type small-signal theory was carried out and found to well explain the experimental results.

DOI： 10.1109/LED.2023.3285938

Reverse Leakage Mechanism of Dislocation-Free GaN Vertical p-n Diodes 査読有り

Kwon, W; Kawasaki, S; Watanabe, H; Tanaka, A; Honda, Y; Ikeda, H; Iso, K; Amano, H

IEEE ELECTRON DEVICE LETTERS 44 巻 ( 7 ) 頁： 1172 - 1175 2023年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Electron Device Letters

The reverse leakage mechanism of threading dislocation (TD)-free gallium nitride (GaN) vertical p-n diode was investigated in various temperature range, and it was compared with that of the p-n diode having a threading dislocation density (TDD) of around 10^6 cm -2. The reverse leakage current was increased markedly by increasing the temperature from 400 K, the dominant mechanism was explained by thermionic and Poole-Frenkel emissions for TD-free and high-TDD p-n diodes, respectively. At high temperatures and electric fields, the leakage current of the high TDD p-n diode showed 2 times higher than the TD-free p-n diode. These results indicate that the performance of vertical GaN devices, especially when employed at high temperatures and electric fields, can be enhanced by removing TDs.

DOI： 10.1109/LED.2023.3274306

Hole mobility limiting factors in dopant-free p-type distributed polarization-doped AlGaN 査読有り Open Access

Kumabe, T; Kawasaki, S; Watanabe, H; Honda, Y; Amano, H

APPLIED PHYSICS LETTERS 122 巻 ( 25 ) 2023年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Letters

We investigated the hole mobility limiting factors in dopant-free p-type distributed polarization-doped (DPD) AlGaN layers by an experimental method. p-DPD AlGaN exhibited a higher hole mobility than GaN:Mg with a similar room temperature hole concentration across all temperature ranges owing to the absence of ionized impurity scattering. In addition, unlike in n-DPD AlGaN, alloy scattering was not always critical in p-DPD AlGaN. The extracted alloy scattering potential was only 0.3 eV, which resulted in a reduced effect of alloy scattering and originated from a small valence band offset in the GaN/AlN heterojunction system. The results suggest that DPD principally enables the fabrication of low-resistance p-type nitride semiconductor thin films as a result of the high hole concentration and high hole mobility.

DOI： 10.1063/5.0155363

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

Cai, WT; Furusawa, Y; Wang, J; Park, JH; Liao, YQ; Cheong, HJ; Nitta, S; Honda, Y; Pristovsek, M; Amano, H

APPLIED PHYSICS LETTERS 121 巻 ( 21 ) 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Letters

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

Tuning the p-type doping of GaN over three orders of magnitude via efficient Mg doping during halide vapor phase epitaxy 査読有り Open Access

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

JOURNAL OF APPLIED PHYSICS 132 巻 ( 14 ) 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

The precise control of Mg concentration ([Mg]) in p-type GaN layers from 2.3 × 1016 to 2.0 × 1019 cm-3 was demonstrated by halide vapor phase epitaxy (HVPE) on n-type GaN (0001) freestanding substrates. [Mg] in GaN layers could be controlled well by varying the input partial pressure of MgCl2 formed by a chemical reaction between MgO solid and HCl gas under the thermodynamic equilibrium condition. In the sample with [Mg] of 2.0 × 1019 cm-3, a step-bunched surface was observed because the surface migration of Ga adatoms was enhanced by the surfactant effect of Mg atoms. The samples show high structural qualities determined from x-ray rocking curve measurements. The acceptor concentration was in good agreement with [Mg], indicating that almost all Mg atoms act as acceptors. The compensating donor concentrations in the samples were higher than the concentrations of Si, O, and C impurities. We also obtained the Mg acceptor level at a sufficiently low net acceptor concentration of 245 ± 2 meV. These results show that the HVPE method is promising for fabricating GaN vertical power devices, such as n-channel metal-oxide-semiconductor field-effect transistors.

DOI： 10.1063/5.0122292

Laser slice thinning of GaN-on-GaN high electron mobility transistors 査読有り Open Access

Tanaka, A; Sugiura, R; Kawaguchi, D; Wani, Y; Watanabe, H; Sena, H; Ando, Y; Honda, Y; Igasaki, Y; Wakejima, A; Ando, Y; Amano, H

SCIENTIFIC REPORTS 12 巻 ( 1 ) 頁： 7363 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

As a newly developed technique to slice GaN substrates, which are currently very expensive, with less loss, we previously reported a laser slicing technique in this journal. In the previous report, from the perspective of GaN substrate processing, we could only show that the GaN substrate could be sliced by a laser and that the sliced GaN substrate could be reused. In this study, we newly investigated the applicability of this method as a device fabrication process. We demonstrated the thinning of GaN-on-GaN high-electron-mobility transistors (HEMTs) using a laser slicing technique. Even when the HEMTs were thinned by laser slicing to a thickness of 50 mm after completing the fabrication process, no significant fracture was observed in these devices, and no adverse effects of laser-induced damage were observed on electrical characteristics. This means that the laser slicing process can be applied even after device fabrication. It can also be used as a completely new semiconductor process for fabricating thin devices with thicknesses on the order of 10 mm, while significantly reducing the consumption of GaN substrates.

DOI： 10.1038/s41598-022-10610-4

Continuous-wave lasing of AlGaN-based ultraviolet laser diode at 274.8 nm by current injection 査読有り Open Access

Zhang, ZY; Kushimoto, M; Yoshikawa, A; Aoto, K; Schowalter, LJ; Sasaoka, C; Amano, H

APPLIED PHYSICS EXPRESS 15 巻 ( 4 ) 2022年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

We demonstrated continuous-wave lasing of an AlGaN-based ultraviolet laser diode, fabricated on a single-crystal AlN substrate when operating at 5 °C. The threshold current density and device series resistance were reduced by improvements to the epitaxial structure and electrode arrangement. A peak wavelength of 274.8 nm was observed for lasing at a drive current over 110 mA, which corresponded to a threshold current density of 3.7 kA cm-2. The operating voltage at the threshold current was as low as 9.6 V.

DOI： 10.35848/1882-0786/ac6198

Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg 査読有り Open Access

Lu, S; Deki, M; Wang, J; Ohnishi, K; Ando, Y; Kumabe, T; Watanabe, H; Nitta, S; Honda, Y; Amano, H

APPLIED PHYSICS LETTERS 119 巻 ( 24 ) 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Letters

We have demonstrated a fabrication process for the Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg. An Ohmic contact with a contact resistance of 0.158 ω cm2 is realized on p-GaN ([Mg] = 1.3 × 1017 cm-3). The contact resistance of p-type GaN with higher Mg concentration ([Mg]=1.0 × 1019 cm-3) can also be reduced to 2.8 × 10-5 ω cm2. A localized contact layer is realized without any etching or regrowth damage. The mechanism underlying this reduced contact resistance is studied by scanning transmission electron microscopy with energy dispersive x-ray spectroscopy and secondary ion mass spectrometry, representing a mutual diffusion of Ga and Mg atoms on the interface. Reductions in the barrier height and surface depletion width with the nitrogen-annealed Mg layer are confirmed by XPS and Hall effect measurements qualitatively.

DOI： 10.1063/5.0076764

Smart-cut-like laser slicing of GaN substrate using its own nitrogen 査読有り Open Access

Tanaka, A; Sugiura, R; Kawaguchi, D; Yui, T; Wani, Y; Aratani, T; Watanabe, H; Sena, H; Honda, Y; Igasaki, Y; Amano, H

SCIENTIFIC REPORTS 11 巻 ( 1 ) 頁： 17949 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

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

Comparative study of quantum efficiency for InGaN photocathodes using various alkali metals Open Access

Idei M., Koizumi A., Sato D., Nishitani T., Honda Y., Amano H.

Journal of Vacuum Science and Technology B 44 巻 ( 1 ) 2026年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B

This study investigated the influence of various alkali metal coatings on the quantum efficiency (QE) characteristics and durability of InGaN photocathodes. The InGaN semiconductor crystal was grown on sapphire substrates using the metal-organic vapor-phase epitaxy method. InGaN photocathodes were fabricated by coating the InGaN surface following heat cleaning in ultrahigh vacuum with Li, Na, K, Rb, and Cs using two methods: the single-alkali metal coating (SAC) method, where only the alkali metal was coated, and the Yo-Yo method, where the alkali metal and oxygen were coated alternately. A negative correlation was observed between the work function of each alkali metal and QE for InGaN photocathodes coated by both the SAC and Yo-Yo methods. For Na, K, Rb, and Cs coatings for both the SAC and Yo-Yo methods, the excitation photon energy dependence of QE showed a threshold near the InGaN bandgap energy. In the excitation power density dependence of QE, the QE reduced exponentially with increasing excitation light power density in the range of 10<sup>−1</sup>–10<sup>5</sup>W/cm<sup>2</sup>. Furthermore, in the durability evaluation, a trend of improved durability with increasing atomic mass of each alkali metal was observed. The durability of the InGaN photocathode with coating Cs/O showed the best performance. In contrast, when Li was used in both the SAC and Yo-Yo methods, the QE was approximately 1 order of magnitude lower than the other alkali metals, and it remained nearly constant regardless of the excitation light power density dependence of QE.

DOI： 10.1116/6.0005129

Characterization of Quaternary Al<sub>x</sub>Ga<sub>1-(x+y)</sub>In<sub>y</sub>N (<i>x</i> ≈ 0.5 and <i>y</i> ≤ 0.12) Metalorganic Vapor Phase Epitaxy Growth Focusing on Unintentionally Incorporated Impurities

Yamada, Y; Kumabe, T; Watanabe, H; Nitta, S; Honda, Y; Amano, H

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 262 巻 ( 12 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Status Solidi B Basic Research

Quaternary AlGaInN has attracted attention because its physical properties such as bandgap, polarization, and lattice constant can be independently changed by controlling the AlN, GaN, and InN mole fractions. However, the complexity of crystal growth is problematic, and reducing unintentionally incorporated impurities that cause carrier scattering and compensation is crucial. In this study, about 30-nm-thick Al<inf>x</inf>Ga<inf>1−(x+y)</inf>In<inf>y</inf>N (x ≈ 0.5 and y ≤ 0.12) is grown on GaN on sapphire by metalorganic vapor phase epitaxy under various growth conditions to systematically analyze the relationship between growth conditions and oxygen and carbon concentrations ([O] and [C], respectively) as well as surface morphology and to elucidate the factors affecting [O] and [C]. [O] is decreased in samples grown at low growth rates and high growth temperatures. This can be attributed to the realization of a smooth surface morphology free of V-pits and trench defects. [C] is decreased in samples grown at a low total of group III source flow rates. The [C] of UID-GaN and that of AlGaInN at various TMI flow rates suggest that TMA mainly affects [C]. Therefore, the key to impurity reduction is to obtain a smooth surface morphology and to promote the adequate decomposition of TMA.

DOI： 10.1002/pssb.202500028

All-GaN-Based Monolithic MIS-HEMT Integrated Micro-LED Pixels for Active-Matrix Displays

Furusawa, Y; Cai, WT; Cheong, HJ; Honda, Y; Amano, H

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 222 巻 ( 23 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Status Solidi A Applications and Materials Science

An all-GaN-based monolithic active-matrix micro-LED system that integrates metal-insulator-semiconductor high-electron-mobility transistors (MIS HEMTs) with light-emitting diodes (LEDs) is demonstrated. The proposed structure employs direct electron injection from the 2D electron gas (2DEG) in a HEMT, serving as the n-type layer, into the quantum wells of the LEDs. A 2-HEMT-1-LED pixel configuration is fabricated with one epitaxial growth, enabling the precise control of LED light output through a combination of select and drive HEMTs. The fabricated pixel achieved a maximum optical output density of 0.5 Wcm<sup>−2</sup>. A 2 × 2 pixel matrix is constructed with row and column lines connected via select HEMTs, demonstrating the capability of the 2-HEMT-1-LED pixel configuration for individual LED control.

DOI： 10.1002/pssa.202500044

Electron Spin Resonance and Photoluminescence Studies of Carbon-Induced Point Defects in GaN: Influence of Doping Concentration and Method

Honda, A; Watanabe, H; Kato, T; Honda, Y; Amano, H

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 262 巻 ( 12 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Status Solidi B Basic Research

The potential to modify the substitution of carbon (C) atom for gallium (Ga) or nitrogen (N) or the occupancy of the interstitial site for the different methods of C doping in gallium nitride is investigated. Herein, two types of samples with C doping concentrations of 1 × 10<sup>17</sup>, 1 × 10<sup>18</sup>, and 1 × 10<sup>19</sup> cm<sup>−3</sup> are prepared by supplying acetylene (C<inf>2</inf>H<inf>2</inf>) gas during growth and C autodoping. Based on the analysis of electron spin resonance and photoluminescence, it appears that the point defect generated by C substitution for the N site (C<inf>N</inf>) is formed in the C-doped sample with C<inf>2</inf>H<inf>2</inf> gas at C concentration of 1 × 10<sup>17</sup> cm<sup>−3</sup>, and the defect changes to the C interstitial (C<inf>i</inf>) at C concentrations of 1 × 10<sup>18</sup>–1 ×10<sup>19</sup> cm<sup>−3</sup>. In contrast, the C<inf>i</inf> defect is formed in the C autodoped samples at C concentrations of 1 × 10<sup>17</sup>–1 × 10<sup>18</sup> cm<sup>−3</sup> and changed to the C<inf>N</inf> defect at C concentration of 1 × 10<sup>19</sup> cm<sup>−3</sup>. These results indicate the possibility that the formation mechanism of yellow luminescence band is different depending on the C doping method even at the same C concentration.

DOI： 10.1002/pssb.202500012

On-State Current Increasing Structure of Source-Connected Polarization Superjunction Transistor

Kokubo E., Watanabe H., Deki M., Tanaka A., Nitta S., Honda Y., Amano H.

Physica Status Solidi A Applications and Materials Science 222 巻 ( 23 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Status Solidi A Applications and Materials Science

A structure is proposed for increasing the on-state current in a polarization superjunction (PSJ) field effect transistor (FET) using gallium nitride (GaN). A PSJ FET can achieve a high breakdown voltage, but in the simplest PSJ FET structure, the PSJ structure and the gate are integrated, so the input capacitance will increase, which is disadvantageous for high-speed switching. Therefore, a structure in which the PSJ structure is connected to the source electrode has been proposed. By connecting the PSJ structure to the source, the capacitance of the PSJ structure is on the output side, where it has little effect on switching. However, those structures suffer from reduced on-state current. To address this issue, a structure is investigated that increases the on-state current because the PSJ structure is etched into a comb shape, and a current path in the on-state is provided separately from the PSJ structure. It is confirmed that the on-state current can be improved by etching the PSJ region. The V<inf>BD</inf>·I<inf>D,sat</inf> product is calculated to evaluate the effectiveness of the comb-shaped PSJ structure. It is possible to improve the V<inf>BD</inf>·I<inf>D, sat</inf> product by 2.17 times compared to the PSJ FET without PSJ structure etching.

DOI： 10.1002/pssa.202500046

Understanding the Ga Polar n-GaN Surface after Mg Diffusion Process

Singh, S; Wang, J; Watanabe, H; Fregolent, M; De Santi, C; Meneghini, M; Badami, O; Asubar, JT; Amano, H; Sarkar, B

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 222 巻 ( 23 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Status Solidi A Applications and Materials Science

This work reports on the control of the n-GaN surface using a simple Mg diffusion process. It is shown that the Mg diffusion process enables a GaN surface without Fermi-level pinning. The process results in the realization of n-GaN unipolar camel diodes where increasing the metal work function leads to an incremental barrier height increase. Notably, the camel diode yields a record Schottky barrier height, indicating the possibility of improving the reverse characteristics of future GaN unipolar diodes.

DOI： 10.1002/pssa.202500090

Highly Oriented Epitaxial Hexagonal Boron Nitride Multilayers on High-Temperature-Resistant Single-Crystal Aluminum Nitride (0001). Open Access

Yang X, Pristovsek M, Nitta S, Honda Y, Ohtake A, Sakuma Y, Hiroto T, Ishida T, Ikezawa M, Guo Q, Amano H

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 12 巻 ( 46 ) 頁： e09354 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advanced Science

The epitaxy of high-quality hexagonal boron nitride (hBN) multilayers on dielectric wafers is essential for hBN applications but remains challenging. Herein, highly-oriented hBN multilayers grown on single-crystal aluminum nitride (AlN)—AlN on sapphire and bulk AlN substrates—via metalorganic vapor phase epitaxy and high-temperature annealing is reported. Hexagonal AlN (0001) not only provides a crystallographically commensurate base for hBN epitaxy but is thermally stable for hBN annealing up to 1800 °C, enabling the first instance of large-area multilayer hBN with both superior out-of-plane and in-plane alignments grown directly on dielectrics using a fully industry-compatible approach. Elevated temperatures also reduce carbon and allow control over the separation of related single photon emission centers in hBN. These centers exhibit a record-narrow wavelength distribution (578 ± 5 nm) with small zero-phonon linewidths down to 1.44 meV, indicating the high uniformity of the achieved multilayer hBN films. This work paves an industry-compatible way toward producing highly-oriented homogeneous hBN multilayers on dielectrics, promising for future device and integration applications.

DOI： 10.1002/advs.202509354

Complete-Mapping Bidirectional Light Communication Using Monolithic III-Nitrides Based Photonic Circuit

Xie M., Qi Z., Wang L., Jiang Y., Gao X., Liang Y., Yuan J., Gao X., Shi Z., Liu Y., Amano H., Guo Y., Wang Y.

ACS Photonics 12 巻 ( 10 ) 頁： 5630 - 5638 2025年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Photonics

III-nitrides based multiquantum well (MQW) structures exhibit unique advantages due to their spectral overlap between electroluminescence and responsivity spectra, facilitating seamless integration of light emission, detection, modulation, and transmission within a single chip. Here, we demonstrate a dynamically reconfigurable bidirectional light communication system using a monolithic III-nitrides based photonic circuit operating approximately in the wavelength range from 385 to 410 nm. Optical isolators and electrical isolation trenches effectively reduce optical and electrical crosstalk down to picoampere levels. Identical MQW diodes interchangeably serve as transmitters and receivers, facilitating simultaneous on-chip transmission of video and audio signals via two parallel optical links. Additionally, the dynamically switchable emitting and detecting functionalities of MQW diodes enable bidirectional communication through a single waveguide, highlighting monolithic III-nitrides photonic integration as a promising approach for next-generation complete-mapping light communication networks and decentralized computational systems.

DOI： 10.1021/acsphotonics.5c01345

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