Improved performance of GaN-based blue LEDs with the InGaN insertion layer between the MQW active layer and the n-GaN cladding layer

In this study, we demonstrate the effect of GaN-based blue light-emitting diodes (LEDs), using an InGaN layer inserted between the n-type GaN cladding layer and the active layer (InGaN/GaN multiple quantum well), on improving device performances. With a 20-mA current injection, the results indicate that the typical output power (or forward voltage) of light-emitting diodes grown with, and without, the InGaN insertion layer are approximately 18.1 (3.1) and 15.3(3.5) mW (V), respectively. This corresponds to an enhancement in output power (wall-plug efficiency) of around 18% (33%), with the use of the InGaN insertion layer. In addition, the electrostatic discharge (ESD) endurance voltages increased from 1000 V to 6000 V when the InGaN insertion layer was applied to the GaN/sapphire-based LEDs. The improvement of output power and ESD endurance voltage could be mainly due to the fact that the Si-doped InGaN insertion layer played the role of a current-spreading layer, which led to a lower possibility of junctions suffering a large current density in specific local sites.