COMPLEX FLOW PHENOMENA IN VERTICAL MOCVD REACTORS - EFFECTS ON DEPOSITION UNIFORMITY AND INTERFACE ABRUPTNESS

The structure of axisymmetric flow patterns in vertical MOCVD reactors is studied with emphasis on their effect on deposition rate uniformity and interface abruptness. Flow visualizations by illuminating TiO//2 seed particles in a sheet of laser light are used to illustrate forced and mixed convection flows. Excellent agreement between experimental observations and model predictions is demonstrated. Simulations show that the film thickness uniformity is affected by susceptor edge, reactor wall and buoyancy effects. Furthermore, nonlinear interactions between transport processes lead to multiple steady flows for typical operating conditions. The deposition of GaAs and AlAs from Ga(CH//3)//3, Al(CH//3)//3 and AsH//3 are used as case studies. Simulations of solid and gas phase concentration transients in the growth of AlAs/GaAs interfaces illustrate the effects flow structures have on interface abruptness.