Surface Morphology Evolution Mechanisms of InGaN/GaN Multiple Quantum Wells with Mixture N₂/H₂-Grown GaN Barrier

Surface morphology evolution mechanisms of InGaN/GaN multiple quantum wells (MQWs) during GaN barrier growth with different hydrogen (H₂) percentages have been systematically studied. Ga surface-diffusion rate, stress relaxation, and H₂ etching effect are found to be the main affecting factors of the surface evolution. As the percentage of H₂ increases from 0 to 6.25%, Ga surface-diffusion rate and the etch effect are gradually enhanced, which is beneficial to obtaining a smooth surface with low pits density. As the H₂ proportion further increases, stress relaxation and H₂ over- etching effect begin to be the dominant factors, which degrade surface quality. Furthermore, the effects of surface evolution on the interface and optical properties of InGaN/GaN MQWs are also profoundly discussed. The comprehensive study on the surface evolution mechanisms herein provides both technical and theoretical support for the fabrication of high-quality InGaN/GaN heterostructures.