In Situ Gravimetric Monitoring of Decomposition Rate from GaN Epitaxial Surface

Decomposition of GaN on its surface was investigated under atmospheric pressure using the in situ gravimetric monitoring (GM) method. Weight change of the GaN substrate both in the H2 carrier gas and in the He carrier gas ambient was monitored at temperatures ranging from 600°C to 950°C with and without the presence of NH3 flow. It was found that the GaN decomposition did not occur in the presence of NH3 flow both in the H2 carrier gas and in the He carrier gas. However, without NH3 flow, the decomposition rate of GaN drastically increased as the temperature increased in the H2 carrier gas, whereas the decomposition of GaN was negligible in the He carrier gas. Dependence of the decomposition rate on the H2 partial pressure in the carrier gas (P H 2 ) was also investigated, and it was found that the decomposition rate is proportional to the P H 2 3/2. These results indicate that the decomposition is governed by the reaction of GaN(surface)+3/2H2(g)→Ga(surface)+NH3(g).