Quantum chemistry study on reaction paths of GaN/AlN grown by MOCVD

The reaction paths of GaN/AlN thin film grown by MOCVD were calculated by quantum chemical calculations with density functional theory. In particular, the temperature effect on the reaction paths between the group-III metalorganic source, TMX and group-V source, NH3 was investigated. The results show that: when T≤473.15 K, TMX and NH3 become ligand adduct TMX:NH3 spontaneously; when T≥573.15 K, TMX:NH3 tends to decompose back into TMX and NH3; when 473.15 K≤T≤573.15 K, the adduct reaction is in equilibrium. When temperature increases, the probability of the formation of amide DMX:NH2 increases. The pyrolysis of TMX and MMX require high temperatures for activation, while DMX into MMX is easier to occur. When T>873.15 K, DMGa into MMGa occurs spontaneously; when T>1273.15 K, DMAl into MMAl occurs spontaneously. With radical CH3 participation, the energy barrier for TMX→DMX (X=Ga, Al) is in between 30-40 kcal/mol, only half of that in direct pyrolysis. With radical H participation, the energy barrier for TMX→DMX (X=Ga, Al) is further reduced, only about 16-20 kcal/mol. Apparently the participation of H radicals will promote the TMX pyrolysis greatly. ©, 2015, Chinese Ceramic Society. All right reserved.