Temperature-Dependent Efficiency Droop in GaN-Based Blue LEDs

The temperature-dependent efficiency droop in InGaN/GaN blue light-emitting diodes (LEDs) has been evaluated. Carrier freeze-out in p-GaN has a strong influence on forward current transport, leading to limited hole density and non-uniform distribution among the quantum wells. Auger recombination is primarily responsible for the observed LED-efficiency droop for temperatures T > 200 K. However, at lower temperatures, electron scan readily tunnel into the p-GaN side to directly compensate Mg acceptors, due to enhanced Coulomb screening. This reduces hole ionization and the emission efficiency. Experimental data agree well with a theoretical model, confirming the dominant role of leakage for the low-temperature efficiency droop.