Computational chemistry predictions of kinetics and major reaction pathways for germane gas-phase reactions

Gas-phase reaction pathways for GeH4 decomposition are proposed and the relevant reaction rates are evaluated by transition-state theory with molecular structures and thermochemical data predicted by ab initio molecular orbital calculations, specifically Hartree-Fock with second-order Moller-Plesset perturbation theory Pressure and temperature effects are included in computed unimolecular reaction rates through the application of Rice-Ramsperger-Kassel-Marcus theory. Quantum-Rice-Ramsperger-Kassel theory is used to estimate the relative rates of stabilization and chemical activation pathways for the insertion of GeH2 into GeH4 to form Ge2H6 and Ge2H4, respectively. The predicted and measured reaction rates agree well with reactions for which experimental kinetic data have been reported. The developed GeH4 decomposition mechanism is subsequently used in a finite-element reactor simulation of germanium deposition to demonstrate the utility of quantum chemistry for developing kinetic rates required in realistic macroscopic models of deposition processes. Contribution of gas-phase reactions to the germanium growth rate is predicted to be important at pressures higher than 1 Torr and temperatures greater than 1000 K.