DFT modeling of chemical vapor deposition of GaN from organogallium precursors. 2. Structures of the oligomers and thermodynamics of the association processes

The thermochemistry of association reactions of organogallium precursors fo r the GaN chemical vapor deposition (CVD) is studied. Geometries, relative energies, and vibrational frequencies of ring and cluster compounds [RGaNR '](n), [R2GaNR ' (2)](m), (n = 2-4, 6; m = 2-3; R, R ' = H, CH3) are obtain ed at the hybrid Hartree-Fock/density functional level of theory (B3LYP/pVD Z). Formation of the [RGaNR '](4) tetramer and [RGaNR '](6) hexamer species is thermodynamically favorable in the gas phase at temperatures up to 720 K (R = H, R ' = CH3) and 920-940 K (R = H, CH3, R ' = H). The thermodynamic analysis of the major gas-phase reactions indicates that association proce sses might play a key role in the GaN CVD under low-temperature-high-pressu re conditions.