The thermochemistry of association reactions of organogallium precursors for the GaN chemical vapor deposition (CVD) is studied. Geometries, relative energies, and vibrational frequencies of ring and cluster compounds [RGaNR′] n , [R 2 GaNR′ 2 ] m , (n ) 2-4, 6; m ) 2-3; R, R′ ) H, CH 3 ) are obtained at the hybrid Hartree-Fock/density functional level of theory (B3LYP/pVDZ). 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′ ) CH 3 ) and 920-940 K (R ) H, CH 3 , R′ ) H). The thermodynamic analysis of the major gas-phase reactions indicates that association processes might play a key role in the GaN CVD under low-temperaturehigh-pressure conditions.