A detailed chemical kinetics model for III-V metalorganic vapor-phase epitaxy (MOVPE) has been developed and tested in conjunction with actual growth data from a novel quartz showerhead vertical reactor. This reactor geometry solves the problem of limited optical access usually inherent in conventional showerhead designs. Emphasis has been put on the surface reactions that are important for the bulk-phase GaAs and InAs growth. Good agreement with available experiments on InGaAs was achieved concerning the growth rates of the film and the In incorporation coefficients. We further investigated the effect of gas inlet design on the growth rate and film concentration distribution. Optimal design and operating conditions are presented that should lead to more uniform films and higher source utilization efficiency over large-area substrates. InGaAs is selected as a model system, however, a variety of other material systems will be discussed (C) 2004 Elsevier B.V. All rights reserved.