Enhancing the light extraction efficiency for AlGaN-based DUV LEDs with a laterally over- etched p-GaN layer at the top of truncated cones

It is known that light extraction efficiency (LEE) for AlGaN-based deep ultraviolet light-emitting didoes (DUV LEDs) can be enhanced by using truncated cone arrays with inclined sidewalls. In this work, the air-cavity-shaped inclined sidewall is applied and the p-GaN layer at the top of the truncated cone is laterally over-etched so that more light escape paths are generated for AlGaN-based DUV LEDs. The experimental results manifest that when compared with DUV LEDs only having the air-cavity-shaped inclined sidewall, the optical power for the DUV LEDs with laterally over-etched p-GaN at the top of the truncated cone is enhanced by 30% without sacrificing the forward bias. It is because the over-etched p-GaN makes little effect on the carrier injection and does not affect the ohmic contact resistance. Moreover, the simulation results show that the truncated cone with laterally over-etched p-GaN layer can enhance the LEE because the reduced p-GaN area can suppress the optical absorption and supplies additional light paths for DUV photos. Then, more light will be reflected into escape cones at the sapphire side. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The light extraction efficiency (LEE) for AlGaN-based DUV LEDs can be enhanced by using air-cavity-shaped inclined sidewalls and laterally over-etched p-GaN layers at the top of truncated cones, which generates more light escape paths. This method increases optical power by 30% without affecting forward bias or carrier injection. Additionally, simulations show that the over-etched p-GaN layer reduces optical absorption and provides extra light paths for DUV photons to improve LEE.