Article
Optics
Yiwei Cao, Quanjiang Lv, Tianpeng Yang, Tingting Mi, Xiaowen Wang, Wei Liu, Junlin Liu
Summary: High-efficiency 278 nm AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) with a bidirectional-staircase-barrier (BSB) structure were studied. The experimental results showed that the proposed BSB structure achieved a maximum external quantum efficiency (EQE) of 8.47% and a wall-plug efficiency (WPE) of 7.01%. Compared to the reference structure, the EQE and WPE were improved by 32% and 31%, respectively. Numerical simulations demonstrated that the BSB structure enhanced electron confinement, improved hole injection, and increased hole concentration in the active region by 170%. The BSB structure also improved the radiative recombination rate and quantum efficiency of the DUV-LEDs.
JOURNAL OF LUMINESCENCE
(2023)
Article
Engineering, Electrical & Electronic
Kangwei Peng, Shouqiang Lai, Mengchun Shen, Saijun Li, Lijie Zheng, Yurong Dai, Jilan Chen, Lihong Zhu, Guolong Chen, Shuli Wang, Hao-Chun Kuo, Yijun Lu, Zhong Chen, Tingzhu Wu
Summary: AlGaN and GaN sidewalls were transformed into AlxGa2-xO3 and Ga2O3, respectively, through thermal oxidation to enhance the optoelectrical characteristics of DUV LEDs. The thermally oxidized AlxGa2-xO3 sidewall greatly improves the light extraction efficiency of lateral light.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Optics
Shudan Xiao, Huabin Yu, Hongfeng Jia, Muhammad Hunain Memon, Rui Wang, Haochen Zhang, Haiding Sun
Summary: In this study, an N-polar AlGaN-based deep-ultraviolet light-emitting diode incorporating a tunnel junction as the p-side contact layer was proposed and demonstrated to have improved performance compared to regular N-polar LEDs.
Article
Optics
Shengjun Zhou, Zhefu Liao, Ke Sun, Ziqi Zhang, Yinzuo Qian, Pengfei Liu, Peng Du, Jingjing Jiang, Zhenxing Lv, Shengli Qi
Summary: This study develops ultrathin tunnel junction (UTJ) deep-UV light-emitting diodes (LEDs) with a low operating voltage of 5.7 V. The formation of Ohmic contact between high-work-function Ni/Au and Mg-Si co-doped n(+)- Al0.45Ga0.55N layer in UTJ is discovered. A high-efficiency sterilization deep-UV light source integrated with 120 UTJ deep-UV LED chips is developed.
LASER & PHOTONICS REVIEWS
(2023)
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
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, Applied
Peng Du, Lang Shi, Sheng Liu, Shengjun Zhou
Summary: Numerical simulation shows that utilizing InAlGaN/AlGaN electron blocking layer can improve the performance of deep ultraviolet LED, especially when optimizing the In composition. Replacing it with InAlGaN/AlGaN superlattice EBL further enhances the performance.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Yusuke Matsukura, Tetsuhiko Inazu, Cyril Pernot, Naoki Shibata, Maki Kushimoto, Manato Deki, Yoshio Honda, Hiroshi Amano
Summary: In this study, the relationship between light output power and the optical thickness of the p-layers in AlGaN-based deep ultraviolet light-emitting diodes was investigated. By adjusting the thickness of the high-Al-composition p-AlGaN clad layer, there was a significant change in light output power, with a maximum of 385 mW achieved at an emission wavelength of 275 nm. The maximum external quantum efficiency reached 15.7% at 10 mA.
APPLIED PHYSICS EXPRESS
(2021)
Article
Materials Science, Multidisciplinary
Xinyi Xia, Sergei Stepanoff, Aman Haque, Douglas E. Wolfe, Simon Barke, Peter J. Wass, Fan Ren, John W. Conklin, S. J. Pearton
Summary: 270 nm AlGaN UV Light-Emitting Diodes (LEDs) were exposed to 1-5 Mrad fluences of Co-60 & gamma;-rays. The highest fluence resulted in a -40% reduction in optical output, without inducing significant midgap emission. The decrease in optical output was attributed to the creation of non-radiative states within the active regions, while the irradiation caused small increases in forward and reverse current.
Article
Optics
Qifeng Lyu, Huaxing Jiang, Kei May Lau
Summary: The study demonstrates the first integration of monolithically integrated UV LEDs and visible-blind UV PDs on Si substrate, achieving high sensitivity and low dark current. By optimizing the structure and materials, it offers potential for various applications with high-performance UV PDs and LEDs.
Article
Chemistry, Multidisciplinary
Mu-Jen Lai, Rui-Sen Liu, Tsung-Yen Liu, Shih-Ming Huang, Ray-Ming Lin, Yi-Tsung Chang, Jian-Bin Wu, Wen-Hong Sun, Xiong Zhang, Lung-Chien Chen
Summary: This paper investigates the use of silicone encapsulation in an AlN-based ceramic lead frame between a UVB-LED chip and a quartz glass cover, resulting in enhanced light output power compared to structures without encapsulation. Although the LOP degradation rates in the two types of silicone-containing packaging were different, they were not correlated with the appearance of cracks in the encapsulating silicone during long-term operation. The slow degradation rates of LOPs in these packaging structures were mainly attributed to the further deterioration of encapsulated silicone after cracks appeared under UVB irradiation.
APPLIED SCIENCES-BASEL
(2021)
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.
Article
Optics
Yu-Hsuan Hsu, Kang-Wei Peng, Yi-Hsin Lin, Ming-Chun Tseng, Su-Hui Lin, Meng-Chun Shen, Ting-Zhu Wu, Zhong Chen, Ray-Hua Horng
Summary: This study fabricated high-voltage, low-current DUV-LEDs with better current spreading and enhanced reflective mirror effect, resulting in higher power output and efficiency compared to traditional devices. It has potential applications in high-voltage circuits to eliminate extra power consumption.
Article
Engineering, Electrical & Electronic
Joosun Yun, Hideki Hirayama
Summary: By optimizing the AlGaN metasurface and comparing different flip-chip structures, it is found that the combination of inclined sidewall and AlGaN metasurface can effectively improve the light-extraction efficiency of AlGaN-based deep-ultraviolet light-emitting diodes.
IEEE PHOTONICS JOURNAL
(2021)
Article
Physics, Condensed Matter
Saad Rasheed, Muhammad Usman, Shazma Ali, Laraib Mustafa, Hamid Ali
Summary: We have utilized AlInGaN graded layers instead of conventional combination of three p-type layers to improve the performance of UV LEDs. The effects of graded quaternary layers on efficiency droop were investigated. Our proposed structure (LED K2) showed a high peak efficiency of approximately 68% and a significantly reduced efficiency droop of -41% compared to LED K1. The improved efficiency in LED K2 can be attributed to enhanced carrier overlap or recombination in the multiquantum wells.
PHYSICA B-CONDENSED MATTER
(2023)
Article
Nanoscience & Nanotechnology
Tianbao Li, Chenyang Liu, Zhe Zhang, Bin Yu, Hailiang Dong, Wei Jia, Zhigang Jia, Chunyan Yu, Lin Gan, Bingshe Xu
Article
Nanoscience & Nanotechnology
Ruimei Yin, Wei Jia, Hailiang Dong, Zhigang Jia, Tianbao Li, Chunyan Yu, Zhuxia Zhang, Bingshe Xu
Summary: The study showed that green InGaN light-emitting diodes utilizing quaternary Al0.05In0.1Ga0.85N quantum barriers with low Al content could effectively reduce the electric field, improve carrier distribution uniformity, alleviate efficiency droop, optimize band pulldown and Fermi levels, thereby enhancing internal quantum efficiency.
Article
Chemistry, Physical
Pengda Huang, Dong Hu, Qingjiang Zhao, Tianbao Li, Bingshe Xu
Summary: InGaN nanorods were grown by a low-cost HCVD method, and p-n heterojunction nInGaN/p-Cu2O photoanodes were successfully constructed by electrodeposition to address the low carrier separation efficiency. The optimized InGaN/Cu2O photoelectrodes with uniform morphology exhibited a maximum photocurrent density of 4.2 mA cm-2 at 1.23 V vs. RHE, which was 8.4 times higher than that of pure InGaN nanorod photoelectrodes. The study demonstrated that constructing p-n heterojunctions greatly enhanced the carrier separation efficiency and alleviated the charge transfer kinetic bottleneck at the photoelectrodes.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Chemistry, Physical
Qingjiang Zhao, Pengda Huang, Dong Hu, TianBao Li, Bingshe Xu
Summary: In this study, a passivation treatment using In2O3 nanoparticles was applied to the surface of hematite, effectively reducing the high-density surface state and improving the photoelectrochemical (PEC) water splitting performance. Additionally, the addition of NiFe(OH)(x) as a cocatalyst further enhanced the kinetics of the oxygen evolution reaction. The optimized Ti-Fe2O3/In2O3/NiFe(OH)(x) compound photoanode achieved a superior photocurrent density of 2.6 mA cm(-2) at 1.23 V vs. RHE, which is more than six times that of pure hematite. This finding offers a potential avenue for overcoming the limitation of high surface-state density in photoelectrodes.