Article
Physics, Applied
R. Akaike, M. Funato, Y. Kawakami
Summary: By using time-integrated photoluminescence and time-resolved PL spectroscopies, we investigated the IQEs of AlGaN/AlN QWs on (0001) c- and semipolar(1 1 over bar 02) r-planes in the far-UVC region. Stronger emissions were observed from r-QWs, especially at shorter wavelengths, indicating higher IQEs compared to c-QWs. The higher IQEs of r-QWs in the far-UVC region were attributed to shorter radiative lifetimes and an increase in a slow decay component, possibly due to a reduction in the number of nonradiative recombination centers. These findings highlight the superiority of the semipolar r-plane for fabricating far-UVC emitting QWs.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Hideaki Murotani, Atsushi Fujii, Ryota Oshimura, Takafumi Kusaba, Kenjiro Uesugi, Hideto Miyake, Yoichi Yamada
Summary: The study found that high-quality AlN templates have a significant impact on the internal quantum efficiency of AlGaN-based MQWs, showing excellent performance in radiative recombination. Even at high excitation power densities and 400 K, nonradiative recombination centers were almost fully saturated.
APPLIED PHYSICS EXPRESS
(2021)
Article
Materials Science, Multidisciplinary
Sebastian Walde, Cheng-Yao Huang, Chia-Lung Tsai, Wen-Hsuang Hsieh, Yi-Keng Fu, Sylvia Hagedorn, Hung-Wei Yen, Tien-Chang Lu, Markus Weyers, Chia-Yen Huang
Summary: The research successfully prepared high-power and high-quality UVC LED by engineering the lattice constants and dislocation densities of various layers in AlGaN-based UVC LEDs, providing an effective strategy for the preparation of corresponding devices.
Article
Materials Science, Multidisciplinary
Muhammad Usman, Tariq Jamil, Sana Saeed
Summary: The influence of the p-AlN layer on electron leakage in 232 nm ultraviolet wavelength light-emitting diodes was numerically investigated. It was found that employing p-AlN not only enhances hole concentration but also suppresses electron leakage notably.
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Ziquan Guo, Zhihui Li, Shouqiang Lai, Xiaoyang Hou, Xiaotong Fan, Chenming Zhong, Yue Lin, Guolong Chen, Guoheng Qin, Tao Gao, Nuoyi Fu, Yuan Shi, Xinqin Liao, Yi Lin, Yijun Lu, Weijie Guo, Zhong Chen
Summary: The temperature-dependent external quantum efficiency (EQE) droop of AlGaN-based UVC-LEDs with different Al contents at wavelengths of 265 nm, 275 nm, 280 nm, and 285 nm was comprehensively investigated. The recombination mechanisms in these UVC-LED samples were analyzed using the modified ABC model, revealing that the contribution of Shockley-Read-Hall recombination exceeds those of Auger recombination and carrier leakage at low electrical-current levels. At high electrical-current levels, Auger recombination and carrier leakage jointly dominate the EQE droop phenomenon. Experimental investigation of the inactivation efficiencies of various UVC light sources against Escherichia coli provides a technical reference for combating COVID-19.
Article
Nanoscience & Nanotechnology
Walter J. Shin, Ping Wang, Yi Sun, Sritoma Paul, Jiangnan Liu, Mackillo Kira, Moe Soltani, Zetian Mi
Summary: In this study, an enhanced Pockels effect in AlN-on-sapphire platform is demonstrated by utilizing AlGaN/AlN multiple quantum wells. Through experiments, resonators with multiple quantum wells show higher resonance shift compared to those without multiple quantum wells. Through a modal overlap analysis, the second-order susceptibility in the multiple quantum wells is found to be approximately 10-20 times higher than that of AlN.
Article
Engineering, Electrical & Electronic
Jianguo Zhao, Jiangyong Pan, Bin Liu, Tao Tao, Daihua Chen, Xianjian Long, Zhe Chuan Feng, Jianhua Chang
Summary: The optical properties of nonpolar AlGaN multiple quantum wells emitting at 280 nm were improved by reducing the densities of superficial pits and basal-plane stacking faults through carefully optimized dual nitridation. This led to a significantly improved emission and an internal quantum efficiency of 39% for nonpolar Al0.43Ga0.57N MQWs at emission wavelength of 279 nm.
IEEE PHOTONICS JOURNAL
(2021)
Article
Engineering, Electrical & Electronic
Tsung-Yen Liu, Shih-Ming Huang, Mu-Jen Lai, Rui-Sen Liu, Xiong Zhang, Yi-Tsung Chang, Lin-Jun Zhang, Ray-Ming Lin
Summary: This paper presents an AlGaN-based narrow-band ultraviolet-B (NB-UVB) light-emitting diode (LED) with a narrow electroluminescence peak and high external quantum efficiency, but with a decrease in light output power under 60 mA DC aging conditions.
ACS APPLIED ELECTRONIC MATERIALS
(2021)
Article
Physics, Condensed Matter
Gwenole Jacopin, Christian Frankerl, Nadine Tillner, Matthew John Davies, Georg Rossbach, Christian Brandl, Marc Patrick Hoffmann, Roland Zeisel, Axel Hoffmann, Hans-Juergen Lugauer
Summary: The influence of growth substrate on the internal quantum efficiency of deep ultraviolet light-emitting diodes was studied, revealing that MQWs grown on sapphire show more efficient carrier localization, leading to an improved IQE of the structure.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Valentin Jmerik, Dmitrii Nechaev, Kseniya Orekhova, Nikita Prasolov, Vladimir Kozlovsky, Dmitry Sviridov, Mikhail Zverev, Nikita Gamov, Lars Grieger, Yixin Wang, Tao Wang, Xinqiang Wang, Sergey Ivanov
Summary: Monolayer-scale GaN/AlN multiple quantum well structures grown on c-sapphire substrates under controllable metal-rich conditions exhibit bright UV emission. The structures have smooth surface topology and absence of stress at certain well thickness, enabling high-power UV emission under specific excitation conditions.
Article
Chemistry, Analytical
Ruiqiang Xu, Qiushi Kang, Youwei Zhang, Xiaoli Zhang, Zihui Zhang
Summary: AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) have great potential in applications such as sterilization, UV phototherapy, and biological monitoring. Although they have advantages in energy conservation, environmental protection, and easy miniaturization, the efficiency of AlGaN-based DUV LEDs is still low compared to InGaN-based blue LEDs. This paper introduces the research background of DUV LEDs, summarizes various methods to improve the efficiency of DUV LED devices from three aspects: internal quantum efficiency (IQE), light extraction efficiency (LEE), and wall-plug efficiency (WPE). Finally, the future development of efficient AlGaN-based DUV LEDs is proposed.
Article
Crystallography
Yi-Tsung Chang, Mu-Jen Lai, Rui-Sen Liu, Shu-Chang Wang, Xiong Zhang, Lin-Jun Zhang, Yu-Hsien Lin, Shiang-Fu Huang, Lung-Chien Chen, Ray-Ming Lin
Summary: This study found that the current droop in AlGaN-based UVB light-emitting diodes is more noticeable at higher temperatures, despite both the main and parasitic peaks decreasing in intensity with increasing temperature. However, the slower temperature droop does not occur when the forward current is increased to temperatures above 298 K. After a 6000-hour aging period, the emission wavelengths do not show obvious changes, while the intensity of the parasitic peak remains nearly unchanged. Therefore, the degradation in light output power during long-term operation is not significantly correlated to the presence of the parasitic peak.
Review
Physics, Applied
Yoichi Yamada, Hideaki Murotani, Noritoshi Maeda, M. Ajmal Khan, Masafumi Jo, Hideki Hirayama
Summary: The study validated an experimental method for evaluating the internal quantum efficiency of semiconductor light-emitting devices by comparing results of efficiency curve analysis with time-resolved photoluminescence spectroscopy. It also observed the significant contribution of excitons to optical gain formation in optically pumped AlxGa1-xN-based multiple quantum wells, potentially leading to higher performance of semiconductor laser diodes.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Jesus Canas, Anjali Harikumar, Stephen T. Purcell, Nevine Rochat, Adeline Grenier, Audrey Jannaud, Edith Bellet-Amalric, Fabrice Donatini, Eva Monroy
Summary: This article discusses the extension of AlxGa1-xN/AlN quantum dot technology for solid-state UV-C sources. It explores the impact of increasing the Al content in the quantum dots and reducing their growth time on the structural and optical properties. The study finds that while the internal quantum efficiency remains around 50% regardless of the Al content or emission wavelength, quantum dots emitting below 270 nm display bimodal luminescence due to fluctuations in their shape.
Review
Materials Science, Multidisciplinary
Muhammad Ajmal Khan, Noritoshi Maeda, Masafumi Jo, Yoichi Yamada, Hideki Hirayama
Summary: In this study, p-AlGaN-based UV-A light-emitting diodes were grown epitaxially in order to solve the problem of light absorption. The use of LP-MOVPE technology allowed for the reduction of threading dislocation density and improvement of internal quantum efficiency, resulting in enhanced performance of the UV-A emitters.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2022)
