Theoretical study on the effect of H₂and NH₃on trimethylgallium decomposition process in GaN MOVPE

We investigate the decomposition process of trimethylgallium (TMGa) during GaN metal organic vapor phase epitaxy in detail by using ab inito calculations. We analyze the decomposition rate of TMGa by estimating Gibbs energy of activation including H2 as well as NH3 effects. Our obtained main reaction pathway of TMGa decomposition is as follows: Ga(CH3)3 + 3H2 + NH3 → Ga(CH3)2NH2 + 3H2 + CH4 → Ga(CH3)2H + 2H2 + NH3 +CH4 → GaCH3HNH2 + 2H2 + 2CH4 → GaCH3H2 + H2 + NH3 + 2CH4 → GaH2NH2 + H2 + 3CH4 → GaH3 + NH3 + 3CH4. Our proposed TMGa decomposition pathway can represent the actual epitaxial growth phenomenon by considering neither polymerization reactions nor radical reactions, which are now widely adopted in fluid simulations of crystal growth. Moreover, our proposed pathway is in good agreement with the experiments.