Optimization of metal-organic chemical vapor deposition regrown n-GaN

GaN devices for high-frequency and high-power applications often need n-doped GaN layers on top of their structures. Such layers can be either grown in an epitaxial reactor or formed by implantation or annealing of Si-containing layers (e.g., a SiO2 mask). These processes are typically performed at high temperatures, which generate the undesired effect of atom diffusion between the different epitaxial layers; consequently, the electrical performance of the final device will be hampered. Herein, an optimized epitaxial growth process of n-GaN layers is developed with the focus on minimizing the atom diffusion process, while preserving a high material quality and excellent electrical characteristics, such as very low contact resistance for n-GaN ohmic contacts or high electron mobility in GaN npin structures. A low growth temperature process combined with improved growth conditions to minimize the incorporation of impurities is successfully optimized and demonstrated on different epitaxial reactors.