Studies on Reduction of Efficiency Droop in InGaN/GaN Multiple Quantum Well LEDs

GaN-based light emitting diodes (LEDs) have attracted extensive attention for their potential applications in energy saving solid-state lightning. However, InGaN/GaN multiple quantum well (MQW) devices suffer from efficiency droop. Although the physical origin of the droop is still under debate, the device structure and material composition play an important role for its minimization. In this simulation work, we have considered LEDs that consist of three pairs of GaN/InGaN layers with thickness values 10 nm/3 nm, respectively forming MQWs. Such MQWs are sandwiched between p-AlGaN electron blocking layer and AlGaN/GaN superlattice insertion layer and have conduction and valence band diagrams of trapezoidal shapes realized by grading In content accordingly. Our results show that for trapezoidal wells the electron and hole distribution peaks occur near the centre of the well thereby increasing the radiative recombination probability. The output power of our proposed LED increases more rapidly with the current density as compared with conventional LEDs. Furthermore, the quantum efficiency of our LEDs reduces 3.92% only in contrast to 34% for conventional LED at the current density of 200 A/cm2.