Abstract:The density functional theory (DFT) of quantum chemistry was used to study the gasphase parasitic reactions in AlNMOCVD growth for UV optoeletronic devices. The reaction pathways of three oligomers of [DMAlNH2]2, [MMAlNH]2 and [MMAlNH]3 with NH3 were investigated, which were related with gaseous nanoparticle generation. By comparing the Gibbs free energy difference of ΔG and transition state barrier of ΔG*, the direction and probability of the related reactions were determined. The results show that there are two competition pathways for [DMAlNH2]2. When T is less than 749 K, the reaction path is dominated by bimolecular reaction with [Al(NH2)3]2 as the product. When T is more than 749 K, it is dominated by intramolecular reaction with [MMAlNH]2 as the product, since the reactions always take the path with lower energy barrier. The other two oligomers of [MMAlNH]2 and [MMAlNH]3 both tend to the bimolecular reaction with NH3 to form the more stable gas products of [AlNHNH2]2 and [AlNHNH2]3 with CH4 elimination. The [Al(NH2)3]2, [AlNHNH2]2 and [AlNHNH2]3 are probably the end gas precursors for surface reactions and for nanoparticle generation in AlNMOCVD process.