Improvement of GaN-based light-emitting diodes using p-type AlGaN/GaN superlattices with a graded Al composition

We investigated the effect of graded Al composition in the p-type AlGaN/GaN superlattices (SLs) of InGaN/GaN multiple quantum well light-emitting diodes (LEDs) to improve their performance. The light output power and external quantum efficiency (EQE) of LEDs with Al composition grading was increased compared with those of LEDs without Al grading, indicating that the efficiency droop was reduced. The improved output power and EQE of LEDs with a graded Al composition was attributed to the increased hole injection by the reduced AlGaN barrier height and the suppression of potential spikes between the graded AlGaN and GaN layers in SLs.