Development of a gas-phase chemistry model for numerical prediction of MOVPE of GaN in industrial scale reactors
A mathematical model has been developed to describe gas-phase chemical transformations during MOVPE of GaN. Attention was paid primarily to the processes of formation and decomposition of the stable adduct compounds as a salient feature of CVD of group III-nitrides. The model relies upon estimation of the thermochemical properties of the feasible adducts, and detection of the predominant gas-phase species and reaction paths. No fitted parameters are necessary for a complete mathematical formulation due to the assumption of the partial equilibrium character of chemical behaviour of the considered gas mixture flows. The chemical model developed has been incorporated into a general numerical model of the MOCVD reactor. The last one is based on the complete Navier-Stokes equations for fluid dynamics simulation and takes into account all important physical processes such as conjugated heat transfer, radiation, multi-component diffusion as well as stiff gas-phase chemical reactions. Numerical simulation of commercial AIXTRON® reactors (a horizontal tube reactor AIX 200 and a multiwafer Planetary Reactor® AIX 2000) have been performed to obtain better understanding and optimization of nitride growth. Experimental growth conditions have been used as input parameters for calculations. Satisfactory agreement with the measured growth rate indicates a quantitatively appropriate prediction.