Investigation of nitridation time on the quality of AlGaN/GaN heterojunction grown on AlN-sputtered sapphire substrate

Abstract The influence of nitridation time on the quality of AlGaN/GaN heterojunction grown on AlN-sputtered sapphire substrate is systematically investigated. The atomic force microscope images show that the samples possess a smooth surface (the root mean square roughness less than 0.4 nm). Raman spectroscopy are performed to explore the residual stress of the samples, the different compressive stress of the samples explain the different two-dimensional electron gas (2DEG) densities between AlGaN/GaN heterojunction. Benefiting from the enhanced crystalline quality, an extremely high electron mobility of 2DEG is realized. More importantly, the mechanism of the nitridation on dislocation evaluation is also revealed and identified by the cross-section transmission electron microscope.