Greatly Enhanced Wall-Plug Efficiency of N-polar AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

In this work, we numerically investigate the N-polar AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) over the Ga-polar DUV LEDs. The light output power has increased from 7.1 mW of Ga-polar DUV LED to 18.8 mW of N-polar DUV LED at 60 mA, and the wall-plug efficiency (WPE) of N-polar DUV LED is boosted by 104% at 60 mA with the same structure of Ga-polar conventional DUV LED. Furthermore, the higher operation voltage of N-polar DUV LED induced by the large energy difference between the p-type interlayer and the p-GaN hole supplier is noted. To reduce the operation voltage of N-polar DUV LED, the structure with a staircase-like p-type interlayer is proposed. The incorporation of staircase-like aluminum composition p-type interlayer mitigates the large potential barrier for holes injection, and the operation voltage is comparable to the Ga-polar DUV LED. The reduced operation voltage further promotes the WPE of N-polar DUV LEDs. Thus, combined with the promoted electron blocking ability and the mitigated potential barrier for holes of N-polar DUV LED, the greatly enhanced WPE is as high as 4.9% at 60 mA, which is 2.88 times higher than the Ga-polar DUV LED.