研究者詳細 - 天野　浩

論文 - 天野　浩

分割表示 867 件中 21 - 40 件目／全件表示 >>

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

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 2025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：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

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

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

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 2025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：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

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 Open Access

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

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 2025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：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

Vertical GaN p-n diode with deeply etched mesas by contactless photo-electrochemical etching Open Access

Toyoda, H; Kwon, W; Watanabe, H; Tsukamoto, R; Furusawa, Y; Itoh, Y; Honda, Y; Amano, H

APPLIED PHYSICS EXPRESS 18 巻 ( 3 ) 2025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：Applied Physics Express

GaN p-n diodes were fabricated by contactless photo-electrochemical (PEC) etching, and their electrical characteristics were evaluated. A high vertical etching rate of 80 nm min<sup>−1</sup>, which is usable for device fabrication etching processes, was achieved using a H₃PO₄ based electrolyte containing S₂O₈<sup>2</sup>⁻ ions and intense UV light. The sidewalls after etching were perpendicular to the substrate owing to the directivity of UV light. Vertical GaN p-n diodes with deeply etched mesas were fabricated by contactless PEC etching and avalanche breakdown was confirmed. The results point to an alternative method of fabricating high-performance GaN power devices.

DOI： 10.35848/1882-0786/adbc43

Normally-off AlGaN/GaN MIS-HEMTs with high 2DEG mobility enabled by shallow recess and oxygen plasma treatment Open Access

Ishiguro, M; Sekiyama, K; Baratov, A; Maeda, S; Igarashi, T; Tajuddin, NSBA; Islam, N; Terai, S; Yamamoto, A; Kuzuhara, M; Sarkar, B; Amano, H; Asubar, JT

JAPANESE JOURNAL OF APPLIED PHYSICS 64 巻 ( 2 ) 2025年2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：Japanese Journal of Applied Physics

We demonstrate a normally-off operation in Al<inf>2</inf>O<inf>3</inf>/AlGaN/GaN MIS-HEMTs with a high two-dimensional electron gas (2DEG) mobility enabled by a shallow recess channel structure and oxygen plasma treatment. In the channel region, the original 25-nm-thick AlGaN barrier layer was thinned down to 9 nm, which in principle, should yield a normally-on operation. However, we show that a pre-insulator deposition oxygen plasma treatment shifts the threshold voltage to +1.4 V. The relatively thick AlGaN barrier facilitated a minimal sacrifice of channel 2DEG mobility retaining a value as high as 1800 cm<sup>2</sup>V<sup>−1</sup>s<sup>−1</sup>, resulting in a high drain current of 600 mA mm<sup>−1</sup>.

DOI： 10.35848/1347-4065/adb256

Fabrication of GaN vertical junction barrier Schottky diode by Mg diffusion from shallow N/Mg ion-implantation segment Open Access

Kwon, W; Itoh, Y; Tanaka, A; Watanabe, H; Honda, Y; Amano, H

APPLIED PHYSICS EXPRESS 18 巻 ( 1 ) 2025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：Applied Physics Express

A vertical GaN p-n junction diode (PND) and junction barrier Schottky diode (JBSD) were fabricated by selective Mg diffusion. Mg was diffused from a shallow N/Mg ion-implantation segment to a depth of 800 nm with a concentration of 1 × 10<sup>17</sup>-3 × 10<sup>18 </sup>cm<sup>−3</sup> by annealing with an AlN capping layer at 1300 ℃ for 5 min under atmospheric N<inf>2</inf> pressure. The PND and JBSD exhibited specific on-resistances of 2.3-2.6 mΩ cm<sup>2</sup> and repeatable breakdowns at 1.95 kV without degradation in breakdown voltage or leakage current. Additionally, the JBSD achieved a high-on/off ratio of 9.1 × 10<sup>7</sup> between 1.5 V and −1 kV.

DOI： 10.35848/1882-0786/ada71a

High-speed modulation of probe current using scanning electron microscope with photocathode technology

Nishitani T., Sato D., Arakawa Y., Niimi K., Yasuda M., Koizumi A., Iijima H., Honda Y., Amano H.

Proceedings of SPIE the International Society for Optical Engineering 13426 巻 2025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：Proceedings of SPIE the International Society for Optical Engineering

Semiconductor inspection technology using e-beam-based voltage contrast (VC) observation provides information on the electrical state and characteristics of terminals with less than 100 nm size, such as the source, drain, and gate in a MOSFET. In VC observation, a nanometer-sized electron beam causes charge accumulation in the target electrode, which is detected as bright or dark according to its electrical state and characteristics. For reproducibility of VC observations for semiconductor inspection, it is essential to release the charge accumulation due to electron beam irradiation of the terminal via leakage currents around the terminal surface. For VC observation of target terminals in the field of view in SEM imaging, electron irradiation time can be used for charge accumulation and unirradiated time for release of charge accumulation within the electron beam scanning. Therefore, it is possible to repeatedly observe VC changes by appropriate selection of the irradiated electron beam current and scanning speed, in addition to the selection of the electron energy. In addition, more fine modulation of the irradiated electron beam current is essential to obtain VC observations with a higher dynamic range, but such modulation should not result in changes in the position or image quality of the SEM image. In this study, an SEM equipped with a photocathode electron gun (PC-SEM) was used to investigate the effect of beam current modulation by photoemission on the SEM image quality of position and focus. Furthermore, in VC observations integrating the local beam current modulation technology of the PC-SEM, the irradiation current was modulated only for the gate plugs in an nMOSFET, and changes in the contrast of the drain plugs were investigated.

DOI： 10.1117/12.3050433

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

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

Physica Status Solidi A Applications and Materials Science 2025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：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

Technological Advancements in AlGaN-Based Deep Ultraviolet Laser Diodes

Kushimoto M., Zhang Z., Yoshikawa A., Aoto K., Honda Y., Sasaoka C., Amano H.

Cs Mantech 2025 2025 International Conference on Compound Semiconductor Manufacturing Technology 2025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：Cs Mantech 2025 2025 International Conference on Compound Semiconductor Manufacturing Technology

AlGaN-based deep-ultraviolet (DUV) laser diodes (LDs) are expected to be applied to various applications such as sterilization, sensing, and laser processing as compact, efficient, and eco-friendly deep-ultraviolet light sources. To realize laser diodes operating in the DUV wavelength range (200 nm to 280 nm), our research group has achieved major breakthroughs such as high-quality AlGaN thin film crystals grown on AlN single-crystal substrates and p-type conductivity control through distributed polarization doping. As a result, pulsed lasing at room temperature was demonstrated. Furthermore, continuous-wave (CW) lasing has been successfully achieved by suppressing dislocation formation through stress concentration suppression and further design improvements. In this presentation, we will review the research results of our group on DUV LD devices and describe the key technologies that played an important role in these achievements.

Sn-doped n-type GaN freestanding layer: Thermodynamic study and fabrication by halide vapor phase epitaxy 査読有り

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

Journal of Crystal Growth 648 巻 2024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：Journal of Crystal Growth

Results of a thermodynamic study of Sn doping and fabrication of a Sn-doped GaN freestanding layer with high structural quality by halide vapor phase epitaxy (HVPE) are described in this paper. Thermodynamic analysis revealed that SnCl2 and/or SnCl act as Sn precursors through the reaction between Sn metal and HCl gas. The equilibrium partial pressures of SnCl2 and SnCl increase with the input HCl partial pressure. To generate Sn precursors effectively, it is desirable that the reaction between Sn metal and HCl gas occurs in the inert gas ambient. On the basis of results of the thermodynamic study, the Sn-doped GaN freestanding layer with a Sn concentration of 5.7 × 1019 cm−3 is fabricated by removing the GaN seed substrate after HVPE growth. The Sn-doped GaN freestanding layer has high crystal quality, and the lattice constants along the c- and a-axes of the Sn-doped GaN freestanding layer are larger than those of the GaN seed substrate because of the high electron density and the size effect of Sn atoms.

DOI： 10.1016/j.jcrysgro.2024.127923

InGaN-based blue and red micro-LEDs: Impact of carrier localization

Park J.H., Pristovsek M., Han D.P., Kim B., Lee S.M., Hanser D., Parikh P., Cai W., Shim J.I., Lee D.S., Seong T.Y., Amano H.

Applied Physics Reviews 11 巻 ( 4 ) 2024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 Reviews

Herein, we investigate micro-light-emitting diodes (μLEDs) ranging in size from 160 × 160 to 10 × 10 μm2 and report that the differences in the behavior of InGaN-based blue (∼460 nm) and red (∼600 nm) μLEDs are related to carrier localization. The external quantum efficiency (EQE) of blue μLEDs decreases with size regardless of sidewall conditions, whereas that of red μLEDs is insignificant due to carrier localization. Atomic probe tomography examination of 30%, 15%, and 7.5% indium-concentrated InGaN layers used in red μLEDs shows that higher indium concentrations result in greater indium fluctuations, which promote carrier localization and thus shorten the diffusion length of carriers. Finally, by observing the peak wavelength of electroluminescence and the current density at peak EQE for both blue and red μLEDs, we find that radiative recombination rate in μLEDs is likely to be chip size dependent.

DOI： 10.1063/5.0195261

(Ultra)wide bandgap semiconductor heterostructures for electronics cooling

Cheng Z., Huang Z., Sun J., Wang J., Feng T., Ohnishi K., Liang J., Amano H., Huang R.

Applied Physics Reviews 11 巻 ( 4 ) 2024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 Reviews

The evolution of power and radiofrequency electronics enters a new era with (ultra)wide bandgap semiconductors such as GaN, SiC, and β-Ga2O3, driving significant advancements across various technologies. The elevated breakdown voltage and minimal on-resistance result in size-compact and energy-efficient devices. However, effective thermal management poses a critical challenge, particularly when pushing devices to operate at their electronic limits for maximum output power. To address these thermal hurdles, comprehensive studies into thermal conduction within semiconductor heterostructures are essential. This review offers a comprehensive overview of recent progress in (ultra)wide bandgap semiconductor heterostructures dedicated to electronics cooling and are structured into four sections. Part 1 summarizes the material growth and thermal properties of (ultra)wide bandgap semiconductor heterostructures. Part 2 discusses heterogeneous integration techniques and thermal boundary conductance (TBC) of the bonded interfaces. Part 3 focuses on the research of TBC, including the progress in thermal characterization, experimental and theoretical enhancement, and the fundamental understanding of TBC. Parts 4 shifts the focus to electronic devices, presenting research on the cooling effects of these heterostructures through simulations and experiments. Finally, this review also identifies objectives, challenges, and potential avenues for future research. It aims to drive progress in electronics cooling through novel materials development, innovative integration techniques, new device designs, and advanced thermal characterization. Addressing these challenges and fostering continued progress hold the promise of realizing high-performance, high output power, and highly reliable electronics operating at the electronic limits.

DOI： 10.1063/5.0185305

Growth and Characterization of High Internal Quantum Efficiency Semipolar (101̅3) GaN-Based Light Emitting Diodes

Hu N., Park J.H., Wang J., Amano H., Pristovsek M.

ACS Applied Electronic Materials 6 巻 ( 11 ) 頁： 7960 - 7971 2024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：ACS Applied Electronic Materials

We report on the growth and characterization of semipolar (101̅3) InGaN/GaN light-emitting diodes (LEDs) on m-plane (101̅0) sapphire with high internal quantum efficiencies (IQEs). Based on earlier work on obtaining untwinned (101̅3) GaN templates on m-plane sapphire, we also succeeded in smoothing the relatively unstable (101̅3) surface using very low V/III ratios during metal-organic vapor phase epitaxy and in the growth of n-and p-doped layers to produce LEDs. Fitting the current-dependent emission, we found high IQEs, up to 86% at 460 nm. The IQEs decreased toward longer wavelengths, similar as for conventional Ga-polar (0001) oriented LEDs. However, the semipolar (101̅3) LEDs have their maximum IQE at much higher current densities than the polar (0001) LEDs due to the higher overlap between electron and hole wave function while maintaining a positive polarization. Together, this makes the (101̅3) orientation very attractive for future blue LEDs.

DOI： 10.1021/acsaelm.4c01312

窒化物半導体結晶の魅力と人・社会・地球への貢献 Open Access

天野浩

日本結晶学会誌 66 巻 ( Supplement ) 頁： s2 - s2 2024年11月

Study on Degradation of Deep-Ultraviolet Laser Diode

Zhang, ZY; Yoshikawa, A; Kushimoto, M; Sasaoka, C; Amano, H

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 221 巻 ( 21 ) 2024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：Physica Status Solidi (A) Applications and Materials Science

The degradation of an AlGaN-based deep-ultraviolet laser diode during operation is studied. A rapid increase in threshold current without any facet mirror damage under direct current stress below the threshold current is observed, which is considered to limit the lifetime of continuous wave lasing to the level of seconds. The evolution of current–light and current–voltage characteristics suggests that the dominant mechanism of degradation is the increased loss of carriers before they can reach the active layer, i.e., the decrease in carrier injection efficiency. The decrease in emission intensity, which is more pronounced at lower current densities, and subsequent increase in sub-threshold current indicate the increase in defect density under current stress, which is similar to the well-analyzed degradation mechanism found in AlGaN-based light-emitting diodes.

DOI： 10.1002/pssa.202300946

Experimental study of gain characteristics in relation to quantum-well width of deep-ultraviolet laser diodes

Zhang Z., Kushimoto M., Yoshikawa A., Aoto K., Sasaoka C., Amano H.

Applied Physics Letters 125 巻 ( 18 ) 2024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：Applied Physics Letters

The gain characteristics of electrically injected AlGaN-based deep-ultraviolet laser diodes were studied with respect to their quantum-well (QW) width dependence by the analysis of the threshold currents and gains for various cavity lengths. Among the fabricated QWs with widths of d = 9, 4.5, and 3 nm, the QW with the smallest width of 3 nm was found to have the highest material gain and lowest transparency carrier density. In contrast to recent arguments in favor of wider QWs for deep-ultraviolet laser diodes, the strategy of narrowing QWs is still found to be effective in practical terms of reducing the threshold current density.

DOI： 10.1063/5.0240488

Discovering the incorporation limits for wurtzite AlP<inf>y</inf>N<inf>1−y</inf> grown on GaN by metalorganic vapor phase epitaxy 査読有り

Yang X., Furusawa Y., Kano E., Ikarashi N., Amano H., Pristovsek M.

Applied Physics Letters 125 巻 ( 13 ) 2024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：Applied Physics Letters

We report on the growth of AlPN on GaN/sapphire templates by metalorganic vapor phase epitaxy using tertiarybutylphosphine (tBP) and NH3 as group-V precursors. P is easy to incorporate into the group-III lattice site, forming PAl anti-site defects and shrinking lattice constants that are even beyond AlN since Al is larger than P. We found that higher temperatures favor P incorporation on the N-sublattice, forming AlPyN1−y, while growth temperatures below 1000 °C result in dominant P incorporation on the Al-sublattice, forming PAl anisites. Similarly, larger NH3 flows stabilize GaN, leading to flat interfaces, but favor the formation of PAl. Furthermore, the P incorporation into AlPyN1−y is non-linear. At very low tBP flows, it initially increases to reach a maximum. Further increasing the tBP flow increases mostly the incorporation of P on the Al-sublattice, and the c-lattice constant decreases again. This leaves a small window of low V/III ratios below 5 and low P/N ratios of 1% or smaller, leading up to ∼4% P incorporation at typical growth temperatures of GaN. However, at such low V/III ratios, GaN is not stable even with N2 carrier gas and requires optimized switching sequences to minimize its decomposition and preserve flat interfaces. Eventually, a 10 nm coherent layer of AlP0.01N0.99 could be reproducibly grown on top of GaN channels with a smooth surface, an abrupt AlPN/GaN interface, and a two-dimensional electron gas with an electron mobility of ∼675 cm2/V s and a sheet carrier density of 1.5 × 1013 cm−2 at room temperature.

DOI： 10.1063/5.0225115

Hole transport mechanism at high temperatures in p-GaN/AlGaN/GaN heterostructure 査読有り

Sikder, B; Hossain, T; Xie, QY; Niroula, J; Rajput, NS; Teo, KH; Amano, H; Palacios, T; Chowdhury, N

APPLIED PHYSICS LETTERS 124 巻 ( 24 ) 2024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

This Letter reports an investigation of hole transport in p-GaN/AlGaN/GaN heterostructures through experimental and theoretical analyses under varied conditions. Highly non-linear current-voltage (I-V) characteristics, obtained via the linear transmission line method measurements, are utilized for this study. At low bias voltage, the transport can be ascribed to the Schottky nature of the contact, while at high bias, the conduction is observed to be governed by space-charge limited current (SCLC). The Schottky characteristics (Schottky barrier height and non-ideality factor) and the SCLC exponent were analyzed for devices with varying contact spacings and at different high temperatures. The SCLC exponent, m, is in the range of 2 ≤ m ≤ 4 depending on the applied voltage range, revealing the existence of the trap states in the channel region. The findings of this work indicate that the charge injection, field-induced ionization, and trap states in the p-GaN channel are critical factors in the current transport of p-GaN/AlGaN/GaN heterostructure.

DOI： 10.1063/5.0203344

Recent advances in micro-pixel light emitting diode technology 査読有り

Park, JH; Pristovsek, M; Amano, H; Seong, TY

APPLIED PHYSICS REVIEWS 11 巻 ( 2 ) 2024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 Reviews

Display technology has developed rapidly in recent years, with III-V system-based micro-light-emitting diodes (μLEDs) attracting attention as a means to overcome the physical limitations of current display systems related to their lifetime, brightness, contrast ratio, response time, and pixel size. However, for μLED displays to be successfully commercialized, their technical shortcomings need to be addressed. This review comprehensively discusses important issues associated with μLEDs, including the use of the ABC model for interpreting their behavior, size-dependent degradation mechanisms, methods for improving their efficiency, novel epitaxial structures, the development of red μLEDs, advanced transfer techniques for production, and the detection and repair of defects. Finally, industrial efforts to commercialize μLED displays are summarized. This review thus provides important insights into the potential realization of next-generation display systems based on μLEDs.

DOI： 10.1063/5.0177550

Impacts of vacancy complexes on the room-temperature photoluminescence lifetimes of state-of-the-art GaN substrates, epitaxial layers, and Mg-implanted layers 査読有り

Chichibu, SF; Shima, K; Uedono, A; Ishibashi, S; Iguchi, H; Narita, T; Kataoka, K; Tanaka, R; Takashima, S; Ueno, K; Edo, M; Watanabe, H; Tanaka, A; Honda, Y; Suda, J; Amano, H; Kachi, T; Nabatame, T; Irokawa, Y; Koide, Y

JOURNAL OF APPLIED PHYSICS 135 巻 ( 18 ) 2024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：Journal of Applied Physics

For rooting the development of GaN-based optoelectronic devices, understanding the roles of midgap recombination centers (MGRCs), namely, nonradiative recombination centers and deep-state radiative recombination centers, on the carrier recombination dynamics is an essential task. By using the combination of time-resolved photoluminescence and positron annihilation spectroscopy (PAS) measurements, the origins of major MGRCs in the state-of-the-art GaN epilayers, bulk crystals, and Mg-implanted layers were identified, and their concentrations were quantified for deriving the capture coefficients of minority carriers. In this article, potential standardization of the room-temperature photoluminescence lifetime for the near-band-edge emission ( τ PL RT ) as the concentration of major MGRCs well below the detection limit of PAS is proposed. For n-GaN substrates and epilayers grown from the vapor phase, τ PL RT was limited by the concentration of carbon on N sites or divacancies comprising a Ga vacancy (VGa) and a N vacancy (VN), [VGaVN], when carbon concentration was higher or lower, respectively, than approximately 1016 cm−3. Here, carbon and VGaVN act as major deep-state radiative and nonradiative recombination centers, respectively, while major MGRCs in bulk GaN crystals were identified as VGa(VN)3 vacancy clusters in Na-flux GaN and VGa or VGaVN buried by a hydrogen and/or VGa decorated with oxygen on N sites, VGa(ON)3-4, in ammonothermal GaN. The values of τ PL RT in n-GaN samples are compared with those of p-GaN, in which τ PL RT was limited by the concentration of VGa(VN)2 in Mg-doped epilayers and by the concentrations of VGaVN and (VGaVN)3 in Mg-implanted GaN right after the implantation and after appropriate activation annealing, respectively.

DOI： 10.1063/5.0201931

　前のページ - 次のページ　