Monolayer GaN/AlGaN LEDs operating in the UV-B band

To date, the performance of AlGaN-based mid and deep ultraviolet (UV) light-emitting diodes (LEDs) is limited by the presence of a high density of defects, quantum-confined Stark effect, inefficient doping, and optical polarization transition from transverse electric to transverse magnetic mode in high Al-content AlGaN quantum wells. In this study, we address some of these fundamental challenges by utilizing monolayer (ML) GaN active regions in AlGaN-based UV LEDs. We show, both theoretically and experimentally, that charge carrier recombination occurs predominantly via the excitonic transition in ML GaN active regions, wherein the exciton binding energy exceeds 0.12 eV. We further demonstrate that double ML UV LEDs emitting at 300 nm exhibit an external quantum efficiency and a wall-plug efficiency of 5.6% and 3.5%, respectively, with excellent spectral stability.