Effects of the substrate thickness and chip area on the light extraction efficiency of chip-scale liquid cup encapsulated AlGaN-based deep-ultraviolet light-emitting diodes

作者：Linbo Hao, Yanan Guo, Dongfang Su, Shen Wang, Xuejiao Sun, Tong Zhang, Xiaojun Jia, Yonghui Zhang, Zi‐Hui Zhang, Xuecheng Wei, Junxi Wang, Naixin Liu, JianYong LI, Jianchang Yan · 发表于：Optics Express · 年份：2025 · DOI：10.1364/oe.579872 · 被引用次数：3 · 研究领域：GaN-based semiconductor devices and materials、ZnO doping and properties、Thin-Film Transistor Technologies

The low light extraction efficiency (LEE) of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) has hindered the explosive growth of the application market. In this study, theoretical calculations reveal that the fluorinated liquid encapsulation can significantly alleviate the total internal reflection (TIR) at both the surface and sidewalls of DUV LED chips. Among various liquid encapsulation schemes, the chip-scale liquid cup shows the largest enhancement in the LEE of DUV LEDs because the inclined sidewall of the liquid cup can redirect light towards the center of the quartz hemisphere. Furthermore, the LEE of DUV LEDs increases with the increased sapphire substrate thickness and the decreased chip area. The trend is attributed to fewer internal reflections and less light absorption before photons reach the chip sidewalls. With the optimized chip encapsulation strategy, a maximum wall-plug efficiency (WPE) of 15% at 2 mA and a fitted LEE of 18.38% were obtained at an emission wavelength of 275 nm.