Simulation of flow and growth phenomena in a close-spaced reactor

Effects of operating conditions and reactor geometry on flow patterns, growth rate and growth rate uniformity in vertical, close-spaced reactors for metalorganic vapor phase epitaxy (MOVPE) are described. Finite element solutions of three-dimensional models of transport phenomena in a close-spaced reactor establish that the individual jets that comprise the gas injector do not penetrate close to the substrate despite its proximity. There is complete mixing of group III and group V reactants in the gas phase prior to any surface reactions. Analysis of growth rate dependence on flow rate, pressure and disk rotation rate shows that ideal stagnation flow can be achieved in a close-spaced reactor. At low rotation rates, growth rate and growth rate uniformity are independent of pressure, even at 1 atm. At higher rotation rates and a reactor height of 16 mm, calculations predict increasing growth uniformity with increasing pressure. The transition from the stagnation flow regime to a classical rotating-disk-reactor regime with increasing reactor height is delineated for various operating conditions. Experiments on the growth of GaAs/AlAs epilayers are consistent with numerical predictions. The applicability of dimensionless number based analysis of close-spaced reactors is also discussed. (C) 1998 Elsevier Science B.V. All rights reserved.