A new, large-scale, barrel-type MOCVD reactor which is capable of pro- ducing seven 3-inch wafers or fourteen 2-inch wafers at a time has been developed. Experiments and computer modelling studies of this geometry have been performed. The physical and electronic properties of n-type GaAs as a function of growth conditions are presented. Through the use of experimental design methods, the growth process has been optimized to yield highly uniform growth rates. The demonstrated uniformity supports the use of this reactor for production environments requiring 3-inch wafers.