High performance deep-ultraviolet light-emitting diodes with transverse electron injection

Abstract

Conventional structure deep-ultraviolet light-emitting diodes (DUV-LEDs) at short wavelengths typically suffer from electron overflow and low light-emitting efficiency. For solar-blind communication application, conventional DUV-LEDs are struggling to simultaneously implement high external quantum efficiency (EQE) and high modulation bandwidth. In this paper, we report that transverse structure LEDs can overcome abovementioned problems and achieve high EQE and high modulation bandwidth. The n-AlGaN free transverse structure LEDs have been demonstrated to yield high crystal quality multiple quantum wells (MQWs). Due to the transverse electron injection, transverse structure LEDs can confine electrons well within the MQWs and avoid electron overflow. To enhance the electron injection and light extraction characteristics, the narrow and long mesa designs were optimized by both experimental and theoretical-fit results. Finite-difference time domain simulation indicates that the n+-GaN layer of the transverse LEDs with the transverse MQWs mesa design does not degrade light extraction. The transverse structure LEDs attain the maximum light output power and EQE recorded to date for DUV-LEDs below 250 nm, respectively 14 mW and 1.72 %. Furthermore, the −3 dB modulation bandwidth can be achieved up to 416 MHz.