Influence of Thickness of p-InGaN Layer on the Device Physics and Material Qualities of GaN-Based LEDs With p-GaN/ InGaN Heterojunction

The influence of the thickness of a p-InGaN layer on the device physics and the material qualities of GaN-based light-emitting diodes (LEDs) are investigated in both numerical and experimental ways. A promoted structure of p-GaN/In0.005Ga0.95N (80/120 nm) heterojunction has been found to remarkably improve the LED's performance. It is demonstrated by the experimental results that the light output power and wall-plug efficiency of such LED increase by 44.63% and 60.66% with a comparison to the conventional LED, respectively. Theoretical calculation reveals that thickening the p-InGaN layer will increase the number of holes accumulating in the p-GaN/InGaN heterojunction and modify the energy band profile of electron blocking layer, which makes it more favorable for carriers to inject into multiple quantum wells (MQWs). However, it is unfortunately found that overthickening the p-InGaN layer will make its crystalline quality degrade and finally affect the MQWs. The thickness of the p-InGaN layer should be carefully controlled at about 120 nm; otherwise, the performance of LED will be severely damaged by the increasing electrical resistance and the enhanced nonradiative recombination in MQWs, which is resulted from the material degradation in p-InGaN layer and MQWs. This paper demonstrates a possibility for achieving high-performance LEDs with the p-GaN/InGaN heterojunction and is of great interest for the commercial development of GaN-based LEDs.