268-nm AlGaN deep-ultraviolet LEDs on AlN substrates with 280 mW output power and wall-plug efficiency above 10% at 500 mA

Abstract

We report 268-nm AlGaN-based deep-ultraviolet light-emitting diodes (LEDs) grown on single-crystal AlN substrates and achieving an optical output power of 280 mW, an external quantum efficiency of 12.1%, and a wall-plug efficiency (WPE) of 10.5% at 500 mA under pulsed operation at room temperature. In sub-270-nm ultraviolet-C (UVC) LEDs on single-crystal AlN substrates, high-current WPE is still limited by insufficient current-injection efficiency and light-extraction efficiency. Here, these limitations are addressed through three complementary design elements: an O2-annealed Ni(2 nm)/Rh(100 nm) p-contact that provides ∼45% reflectance at 268 nm while reducing the forward voltage relative to a conventional Ni/Au contact; an optimized multiple-quantum-well active region incorporating a thin high-Al-content last quantum barrier before the last quantum well to redistribute radiative recombination and suppress overflow-related droop; and a hemispherical quartz lens attached to the AlN substrate backside to improve light extraction. These results demonstrate an effective design strategy for achieving high-power, high-efficiency operation in sub-270-nm UVC LEDs.