Faculty Profiles - AMANO, Hiroshi

Papers - AMANO, Hiroshi

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Characteristics of 2DEG generated at the heterointerface of an AlN/GaN structure grown on an AlN substrate using metal organic vapor phase epitaxy Open Access

Yoshikawa, A; Kumabe, T; Sugiyama, S; Arai, M; Suda, J; Amano, H

JOURNAL OF APPLIED PHYSICS Vol. 137 ( 19 ) 2025.5

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

A pseudomorphic AlN/GaN structure was grown on an AlN substrate using metalorganic vapor phase epitaxy (MOVPE). The Hall effect characteristics of two-dimensional electron gas induced at the interface between AlN and GaN and the properties of high-electron-mobility transistors (HEMTs) fabricated using the proposed AlN/GaN structures were investigated. The Hall effect measurements indicated that the electron mobility at room temperature was 294 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup>, the sheet carrier density was 1.1 × 10<sup>13</sup> cm<sup>−2</sup>, and the sheet resistance was 1930 Ω/sq. Cross-sectional transmission electron microscopy images revealed an extremely abrupt interface between the AlN and GaN layers. By contrast, surface atomic force microscopy measurements indicated that GaN exhibited a clear step-terrace surface and the AlN barrier layer exhibited the signs of transitioning to island-like growth. Furthermore, the HEMT devices exhibited clear transistor characteristics with a source-drain breakdown voltage of 2.3 kV and an ON/OFF ratio of >10<sup>7</sup>. These findings demonstrate the potential of MOVPE for fabricating AlN/GaN on AlN substrates, showing the inherent potential of AlN as a substrate.

DOI： 10.1063/5.0255068

Quantum efficiency characteristics of low-threading-dislocation-density InGaN photocathode grown on GaN substrate

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

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Vol. 43 ( 3 ) 2025.5

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

The dependence of the quantum efficiency (QE) of a Cs/O-activated negative-electron-affinity (NEA) state InGaN photocathode on threading dislocation density (TDD) was investigated. InGaN photocathodes with different TDDs were grown on sapphire and GaN substrates by metal-organic vapor-phase epitaxy (MOVPE). The TDDs were 1 × 10<sup>9</sup> cm<sup>−2</sup> on the sapphire substrate and less than 5 × 10<sup>6</sup> cm<sup>−2</sup> on the GaN substrate. After the activation of the NEA state of InGaN photocathode surfaces by Cs/O, the QEs were 1.1% on the sapphire substrate and 0.91% on the GaN substrate. Despite a TDD difference of approximately two orders of magnitude, the QEs were comparable. The results show that the QE is not limited by the high TDD in the InGaN photocathode.

DOI： 10.1116/6.0004199

Modeling and Designing a GaN-Growth Reactor With Halogen-Free Vapor Phase Epitaxy: NH<sub>3</sub> Decomposition at the Catalytic Surface of Components to Replicate Parasitic Polycrystal Formation Open Access

Shimazu, H; Nishizawa, SI; Nitta, S; Amano, H; Nakamura, D

IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Vol. 38 ( 2 ) page： 311 - 323 2025.5

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Semiconductor Manufacturing

Achieving long-duration, large bulk GaN growth is crucial to supply low-cost, high-quality GaN. Halogen-free vapor phase epitaxy (HF-VPE) is a promising method for bulk GaN growth but faces challenges due to severe polycrystals deposition on reactor components, such as the source-gas nozzles, which impedes stable, extended growth. In this study, we developed models to simulate the polycrystal deposition in HF-VPE-GaN growth conditions by including surface reactions of GaN formation and NH3 decomposition. Moreover, we devised conditions for controlling gas flow and interdiffusion to suppress polycrystal deposition around the source-gas nozzles. Experimental results aligned with simulations, showing that increasing the distance between Ga and NH<inf>3</inf> nozzles and replacing the sheath gas from H<inf>2</inf> to N<inf>2 </inf>effectively minimized polycrystal formation. The findings confirm that reducing NH<inf>3</inf> concentration through catalytic surface decomposition on refractory components is crucial to polycrystal suppression. Optimizing nozzle dimensions and gas species synergistically controls the gas flow and interdiffusion. The constructed models contribute to advancing the design of polycrystal suppressive structures and conditions for long-duration bulk GaN growth.

DOI： 10.1109/TSM.2025.3558328

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 2025.4

Language：English Publishing type：Research paper (scientific journal) Publisher：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 2025.4

Language：English Publishing type：Research paper (scientific journal) Publisher：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 2025.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 18 ( 3 ) 2025.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 64 ( 2 ) 2025.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 18 ( 1 ) 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 13426 2025

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

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

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

Advances in Deep Ultraviolet Semiconductor Laser: From Material Challenges to Device Performance

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

2025 Conference on Lasers and Electro Optics Europe and European Quantum Electronics Conference CLEO Europe Eqec 2025 2025

Language：English Publishing type：Research paper (scientific journal) Publisher：2025 Conference on Lasers and Electro Optics Europe and European Quantum Electronics Conference CLEO Europe Eqec 2025

AlGaN-based deep ultraviolet (DUV) laser diodes (LDs) have garnered significant attention for a wide range of applications, including sterilization, sensing, and high-precision laser processing, owing to their compact size, high efficiency, and environmentally friendly properties. Despite these advantages, achieving practical device performance has been challenging due to the difficulty in realizing high-quality crystal growth and efficient carrier injection.

DOI： 10.1109/CLEO/EUROPE-EQEC65582.2025.11110927

Magnesium Intercalation in Gallium Nitride for Enhanced P-Type Doping and Device Performance

Wang J., Amano H.

Proceedings of the 16th IEEE International Conference on Electron Devices and Solid State Circuits Edssc 2025 page： 52 - 54 2025

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the 16th IEEE International Conference on Electron Devices and Solid State Circuits Edssc 2025

P-type doping in gallium nitride (GaN) has traditionally relied solely on substitutional magnesium (Mg) incorporation. However, persistent limitations such as low hole mobility, limited hole concentration, and poor ohmic contact remain unresolved. Interstitial magnesium, long regarded as a deep-level compensating impurity detrimental to p-type doping, exhibits unexpected behavior at exceptionally high concentrations. This study demonstrates that, under such conditions, interstitial Mg atoms self-organize into aligned single-atomic layers, a phenomenon known as intercalation. Each Mg layer induces periodic polarity transitions in GaN, which may account for the experimentally observed increase in ionized acceptors and hole concentration post-intercalation. Furthermore, the uniaxial strain generated by these interstitial Mg layers modifies the valence band structure and enhances hole mobility. These synergistic advantages are attributed to '2D-doping' effects which offer fresh insights into semiconductor doping mechanisms. Crucially, achieving this 2D-doping regime requires only thermal annealing of a metallic Mg thin film deposited on GaN, offering a scalable and industrially viable pathway to overcome the constraints of conventional substitutional Mg doping. This discovery holds broad implications for optoelectronic and power device applications.

DOI： 10.1109/EDSSC64492.2025.11182923

Sn-doped n-type GaN freestanding layer: Thermodynamic study and fabrication by halide vapor phase epitaxy Reviewed Open Access

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

Journal of Crystal Growth Vol. 648 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 11 ( 4 ) 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 11 ( 4 ) 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 6 ( 11 ) page： 7960 - 7971 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 66 ( Supplement ) page： s2 - s2 2024.11

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 Vol. 221 ( 21 ) 2024.11

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

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