ABINITIO MOLECULAR-ORBITAL STUDY OF THE GAAS HYDRIDES

The interaction of GaH(x) (x = 0-3), electron deficient in the valence shell, and of AsH(x) (x = 0-3), electron rich in the valence shell, has been studied by using ab initio molecular orbital methods, which include Moller-Plesset correlation corrections to the fourth order, MP4SDTQ. In most instances, Hartree-Fock (HF) optimizations were used to determine local minima, and in a few cases, MP2 = Full optimizations or MCSCF optimizations were also employed. This research corroborates the work reported by others for the electronic states of GaH, GaH2, GaH3, AsH, AsH2, AsH3, and GaAs. We report two structures for (GaAs)2(dimer); the lowest energy conformer appears to be a special case of mu-bridged Ga-As2-Ga. Monovalent Ga is proposed to explain the lowest energy structure of GaAsH2. The lowest energy tetrahydride, H2Ga-AsH2, is a classical Lewis structure. A double Lewis acid/base adduct, (H2Ga-AsH2)2, which can be interpreted in terms of mu-bridging, is the dimer structure. This research supports the formation of Lewis acid/base adducts in the thin-film deposition of GaAs by chemical vapor deposition.