Quantum chemical study on gas-phase oligomerization in AlGaN MOCVD growth

The gas-phase oligomerization reaction path in the growth of AlGaN by MOCVD has been calculated using quantum chemical calculations with density functional theory. The oligomerization of two types amides DMAlNH2 and DMGaNH2 (including heterogeneous oligomerization and homogeneous oligomerization) and subsequent CH4 elimination reactions were investigated at different temperatures. The degree for formation of the various oligomers and the different types of oligomers that could appear at different temperature ranges has been analyzed. DMAlNH2 has a stronger oligomerization ability than DMGaNH2, and the presence of DMAlNH2 can promote DMGaNH2 to form heterogeneous oligomers, which successfully explains the gas phase scavenging effect. Dimers are mainly oligomers in gas phase and their CH4 elimination reactions are mainly intramolecular reactions rather than intermolecular reactions. Pure gas [MN] or [GaN] molecules are theoretically impossible to form.