Cathodoluminescence characteristics of large-scale in-rich InGaN grains and effect of low-energy electron-beam irradiation

GaN and InGaN single-layer and InGaN/GaN multi-quantum-well (MQW) structure s were grown in sequence on sapphire (0001) substrates by using metalorgani c chemical vapor deposition, and the luminescence characteristics: of each layer were investigated employing room-temperature cathodoluminescence (CL) . Large-scale In-rich grains several microns in width were observed in the monochromatic CL image, presumably formed at the InGaN MQW layer. The CL sp ectra measured at In-rich grains showed a slight red-shift and an enhanced peak intensity. The effect of low-energy electron beam irradiation on the l uminescence characteristics of each layer was investigated, and a monotonic decrease of the peak intensity was observed as a function of the irradiati on dose. The reduction ratio of the normalized integrated intensity due to irradiation damage was found to be lower in In-rich InGaN than in GaN.