SIMULATION OF CARBON DOPING OF GAAS DURING MOVPE

We present a kinetic model for carbon incorporation during metalorganic vapor phase epitaxy (MOVPE) of GaAs, using trimethylgallium (TMG) and either arsine (AsH3) or trimethylarsenic (TMAs) as growth precursors. The proposed mechanism for the TMG-TMAs-AsH3-H-2 system involves 20 gas phase species, 23 gas phase reactions, 14 surface species and 64 surface reactions. The proposed carbon incorporation mechanism is based on the surface formation of Ga-carbene species leading to carbon placement on the arsenic lattice position as observed experimentally. The kinetic mechanism is implemented in a simple reactor model to allow investigations of the reaction pathways without additional complications arising from simulation of complex transport phenomena. The reaction mechanism reflects reported decomposition data for the reactants. Model predictions of carbon concentration levels are in good agreement with published trends in carbon incorporation levels with temperature and the V/III ratio. In particular, the model predicts high carbon incorporation rates when using TMAs and a reduction in carbon concentration levels as AsH3 is added to the reaction mixture in increasing amounts.