Performance enhancement of ultraviolet light-emitting diodes by manipulating Al composition of InGaN/AlGaN superlattice strain release layer

InGaN/AlGaN ultraviolet light-emitting diodes (UV LEDs) suffer from residual in-plane compressive stress and poor carrier injection efficiency. Here, we simultaneously reduce the stress and improve the carrier concentration in In0.018Ga0.982N/Al0.05Ga0.95N multiple quantum wells by optimizing the Al composition of the underlying InGaN/AlGaN superlattice strain release layer (SRL). On the one hand, higher Al composition of SRL can reduce the residual in-plane compressive stress of epilayers, which is beneficial for increasing radiative recombination rate. On the other hand, higher Al composition can enhance the effective barrier height in SRL, which can decelerate electrons and prevent holes from transporting into the n-region. As a result, the light output power of UV LEDs with In0.01Ga0.99N/Al0.06Ga0.94N SRL is 19.3% higher than that of UV LEDs with In0.01Ga0.99N/Al0.02Ga0.98N SRL at 100 mA.