The influence of reactor pressure on rate-limiting factors and reaction pathways in MOVPE of GaAs

Abstract

A quantitative model for homoepitaxial deposition of GaAs on (111)Ga using Ga(CH 3) 3 and AsH 3 has been extended to consider the effects of temperature, flow rate, and inlet gas composition on the process behavior at different reactor pressures. When the pressure is reduced, surface kinetics and thermal diffusion become more important relative to gas-phase reactions and diffusion, although the extent of the shift depends on the method used to lower the pressure. In addition, the dominant species and reaction pathways change with operating conditions, e.g., some species that adsorb at atmospheric pressure tend to desorb preferentially when the pressure is lower. Results for impinging-jet and rotating-disk reactors indicate that the relative importance of diffusion and kinetics is dependent on the reactor configuration. However, the different systems exhibit similar trends in behavior, and these trends agree closely with available experimental data. The model also shows that neither replacement of H 2 carrier gas with He nor addition of CH 4 to the inlet gas mixture have an appreciable effect on the process behavior over a wide range of operating conditions.