Reduction of efficiency droop in InGaN-based blue LEDs

We have investigated the efficiency droop in InGaN based multiple-quantum light-emitting diodes (MQWs-LEDs) and double hetero-structure light-emitting diodes (DH-LEDs) by changing the barrier (both thickness and barrier height) within quantum wells. Our results show that for MQW-LEDs, with the decrease of barrier width from 12nm In 0.01 Ga 0.99 N to 3nm In 0.01 Ga 0.99 N, the external quantum efficiency (EQE) droop point is increased from 350 Acm -2 to >1000 Acm -2 , and the slope of EQE drop is also greatly reduced. When the barrier height of the MQW-LEDs is decreased, i.e. barriers changed from In 0.01 Ga 0.99 N (3nm) to In 0.06 Ga 0.94 N (3nm), the EL intensity is reduced to half. In the case of DH-LEDs, 6nm DH-LED shows the highest EL intensity and no EQE droop up to 1000 Acm -2 . When the active region of the DHLED is increased from 6nm to 12nm, the electroluminescence (EL) intensity is reduced to 70% of that of the 6nm DHLED, and the EQE shows negligible droop compared to the 6nm DH-LED due to both enhanced hole injection and reduced electron overflow. These results suggest that heavy effective mass of holes and low hole injection efficiency (due to relatively lower p-doping) leading to severe electron leakage are responsible for the efficiency droop.