Enhanced light output power from AlGaN-based deep ultraviolet LEDs achieved by a four-in-one mesa structure

This study aimed to investigate the impact of mesa geometry on the light output characteristics of AlGaN-based 275 nm deep ultraviolet light-emitting diodes (DUV-LEDs). By dividing the original single-junction mesa into four parts and connecting them serially (four-in-one), high-voltage (HV) DUV-LEDs with rectangular, hexagonal, circular, triangular, and square submesas were realized, achieving significant enhancement of the light output power (LOP) and wall-plug efficiency (WPE). The LOP of HV DUV-LEDs with hexagonal submesas has been promoted substantially compared to that of the original DUV-LEDs. Among the investigated five different types of submesas, hexagonal-type HV DUV-LEDs can achieve the highest LOP and WPE due to the higher sidewall light extraction. Furthermore, it is also demonstrated that pulse current driving can reduce the self-heating effect of HV DUV-LEDs.