Films of varying composition were deposited on masked InP substrates using metalorganic chemical vapor deposition and the selective area epitaxy technique. The growth rate enhancement and perturbed composition as a function of mask geometry were measured for each film and also calculated using a vapor phase diffusion model which incorporated an indium diffusion parameter and a gallium diffusion parameter. The parameters were found to be a function of film composition. Consideration of the physical meaning of the parameters suggested that the gallium incorporation constant increased in the high wavelength alloys. An InGaAs film was deposited on a substrate masked with a dielectric pattern of the type used in the fabrication of integrated photonic devices, An increase in modeling accuracy was obtained using knowledge of the alloy composition dependence in the modeling parameters. (C) 2002 Elsevier Science B.V. All rights reserved.