Numerical study of AlGaN growth by MOVPE in an AIX200 RF horizontal reactor

The prediction of MOVPE processes requires the modelling of numerous coupled transport phenomena for momentum, mass and heat including temperature dependent physical properties and chemical reactions. In the present paper, the numerical simulation is used as a tool to identify and distinguish systematically the important parameters in the AlGaN growth process. A reliable prediction of the essential parameters in MOVPE production devices, in particular of the deposition rates, requires accurate model parameters and realistic approximations of operating conditions entering as boundary conditions in the simulation process. However, the lack of microscopic data for the transport phenomena of the participating gases and the uncertainties in quantifying the reaction kinetics are major obstacles towards the use of the numerical simulation as a reliable design tool. To overcome this difficulty, a systematic study of the AlGaN growth process is presented. The sensitivity of different approaches for the computation of gas-mixture transport coefficients with respect to the heat and mass transport and thus, the deposition rates, is studied. For the chemistry mechanisms under consideration, the rates of reactions for the adduct and oligomer formation and decomposition are studied. These data were predicted in accordance with the corresponding data available in the literature. According to the results obtained, the adduct and oligomer formation is much more important in the AlN growth process than in the GaN growth process. The presented parametrical variations allow the assessment of the models used. Besides that, they allow to distinguish the main reaction pathways and thus to improve the understanding of the chemical kinetics. In order to confirm that, experimental results are presented for validation wherever possible.