SPA Monitoring of GaN Movpe Surface

ABSTRACTFor the purpose of clarifying the growth mechanism of GaN metal-organic vapor phase epitaxy (MOVPE), the GaN surface during the growth on the (0001) sapphire substrate were in-situ monitored by surface photo-absorption (SPA) method. Ga-rich and N-rich surfaces can be distinguished by their reflectivities. It is found that the surface stoichiometry changes with the substrate temperature and with the carrier gas. In the nitrogen carrier gas, a N-rich GaN surface is stably formed at temperatures up to about 1000°C under NH3 flow. In contrast, the surface in H2 carrier gas is N-rich below 720°C, but becomes Ga-rich above 850°C. The desorption kinetics indicates that H2 enhances the N desorption.