Efficiency enhancement of ultraviolet light-emitting diodes with segmentally graded p-type AlGaN layer

Wang Lin-Yuan¹, Song Wei-Dong¹, Hu Wen-Xiao¹, Li Guang¹, Luo Xing-Jun¹, Wang Hu¹, Xiao Jia-Kai¹, Guo Jia-Qi¹, Wang Xing-Fu¹, Hao Rui³, Yi Han-Xiang³, Wu Qi-Bao^{2, ‡}, Li Shu-Ti^{1, §}

(a) Light output power and (b) normalized internal quantum efficiency as a function of injection current for the four LEDs. The inset in panel (a) is the EL spectrum collected at injection current of 100 mA.