Improvement of blue InGaN/GaN light-emitting diodes with graded indium composition wells and barriers

We present a numerical study on the effect of graded indium well and barrier structures having different compositions in InGaN/GaN-based light-emitting diodes (LEDs) on their optical and electrical properties. Compared with conventional LEDs, the output power of the proposed LEDs was found to increase by a factor of ~2.4, and the efficiency droop reduced greatly. In addition, the turn-on voltage was reduced by using an InGaN well and barrier structure having a graded indium composition. These improvements are believed to result from the enhancement in the hole-injection efficiency, as well as the spatial distribution overlap between the electrons and holes in multiple quantum wells.