MOLECULAR-ORBITAL CALCULATIONS ON METHYL ALKYLS AND HYDRIDES USED IN THE ORGANOMETALLIC VAPOR-PHASE EPITAXY OF SOME III-V-SEMICONDUCTOR FILMS .1.

We report ab initio and semiempirical calculations of the equilibrium geometries, bond strengths, and vibrational spectra of NH3, PH3, AsH3, (CH3)3Al, (CH3)3Ga, (CH3)3In, N(CH3)3, P(CH3)3, As(CH3)3, and some of their derived adducts as a function of basis set and of self-consistent field approximation. We compare our results to recent IR and Raman data, and to standard thermochemical data. We obtain very good agreement with experimental geometries, good agreement with experimental bond strengths, and only fair agreement (10%-20%) with experimental vibrational spectra. We argue that this purely theoretical approach is, with qualification, appropriate for predicting thermochemical parameters for gas-phase reactions that occur in organometallic vapor phase epitaxy of III-V semiconductor thin films. We expect to make reasonable predictions for barriers to chemical reactions, while use of our predictions of free energies will probably require care.