The Effect of Nanometer‐Scale V‐Pit Layer on the Carrier Recombination Mechanisms and Efficiency Droop of GaN‐Based Green Light‐Emitting Diodes

Abstract

The effects of nanometer‐scale V‐pits layer with different parameters on the carrier recombination mechanisms and efficiency droop of GaN‐based green light‐emitting diodes (LEDs) are investigated. Under optimized growth conditions, the threading dislocations (TDs) are surrounded by V‐pits layer with six (10–11) side wall facets. The V‐pits layer contains sidewall multiple quantum wells (MQWs) with bandgap several hundred millielectronvolts higher than that of c‐plane MQWs. This higher bandgap acts as a barrier for carriers and prevents them from reaching the dislocations, which can effectively suppress the nonradiative recombination. Analysis suggests that the V‐pits enhance hole injection into deeper MQWs, which is confirmed by the secondary ion mass spectroscopy profiles of Mg and Al. With the aid of the V‐pits layer, holes can be injected into deeper MQWs, which reduce the carrier concentration within individual QWs. Therefore, the Auger‐related efficiency droop can be suppressed. The results show that LED with 200 nm LT‐GaN + 40 nm n‐GaN V‐pits layer is able to deliver an improvement in the light output power by 189% as compared with reference LED without V‐pits layer. At 200 mA, the efficiency droop for LED with200 nm LT‐GaN + 40 nm n‐GaN V‐pits is 25.9%, which is much smaller than 34.7% for reference LED without V‐pits.