The effects of material intermixing, group V atom desorption and exchange on the surface morphology of InP wetting layers on GaAs substrates were studied by varying the growth temperature and coverage in metalorganic vapor phase epitaxy. Tertiarybutylphosphine (TBP) was used as the phosphorus source and the surface morphology was characterized by atomic force microscopy. The observations showed that the morphology depends strongly on the growth parameters and deteriorates with increasing temperature and decreasing InP coverage. It was verified that the main reason for the morphology impairment is the strongly temperature dependent group V atom exchange and desorption within several monolayers on the sample surface during exposures of the GaAs surface to TBP. However, a smooth morphology could be obtained within a wide temperature range by depositing at least a complete monolayer of InP. (C) 2004 Elsevier B.V. All rights reserved.