Robust reaction-transport models of MOVPE reactors

A simple gas-phase and surface kinetic model describing the Metallorganic Vapor Phase Epitaxy (MOVPE) of GaAs from trimethyl-gallium (TMG) and arsine has been extracted from reported reaction mechanisms through sensitivity analysis. This model was coupled with fundamental descriptions of the flow, heat and mass transfer in MOVPE reactors. All the uncertainties of the model were lumped into the two rate constants of the surface growth reaction. Finite element simulations of GaAs growth in a rotating-disk MOVPE reactor reported in the literature were used to fit the two unknown rate constants. Without any adjustment, the model could predict observed growth rates at higher susceptor rotational rates. A more serious robustness test was the fully coupled 2-D simulation of GaAs growth in a horizontal MOVPE reactor by using a state-of-the-art code (MPSalsa) developed at Sandia National Laboratories. The model predicted observed growth rates reasonably well in 2-D fully coupled simulations of flow, heat and mass transfer. Further development of the kinetic model by testing different kinetic scenario in 2- and 3-d simulations and by using data obtained at kinetically-limited growth conditions is planned in order to develop a reactor-independent simulator of the MOVPE of GaAs. Such a model will be essential for the development of a conceptual virtual MOVPE reactor, which can be used for reactor design, optimization and model-based control.