Efficiency of light emission in high aluminum content AlGaN quantum wells

Abstract

High quality multiple quantum well ${\mathrm{Al}}_{0.35}{\mathrm{Ga}}_{0.65}\mathrm{N}$ active layers with narrow wells designed for ultraviolet (UV) light-emitting diodes using the phonon engineering approach are characterized using quasi-steady-state and time-resolved photoluminescence spectroscopy. The photoluminescence intensity decrease with temperature increasing from $10\text{to}300\mathrm{K}$ was very small, and the upper limit of the internal quantum efficiency (IQE) of up to 70% was estimated based on this temperature dependence. Carrier lifetime measurements yielded the lower bound of the IQE to be $\sim 35\%$ under optical pumping, whereas IQE of $\sim 25\%$ was estimated from the measured external quantum efficiency and the light extraction efficiency calculated by ray tracing. The observed photoluminescence features and the high IQE are interpreted as a consequence of strong carrier (exciton) localization.