The authors report comparative studies of the deposition of GaP on (001) GaAs, as-polished (001)Si, SiO2-coated (001)Si, nanoscopically roughened (001)Si, and polycrystalline GaP surfaces by organometallic chemical vapor deposition using trimethylgallium (TMG) and phosphine (PH3) sources. The thicknesses of the GaP films increase or decrease exponentially toward the edge of wafers. This functional dependence implies one-dimensional gas-phase diffusion of a reactive species, possibly H-P=Ga-CH3, generated by heterogeneous catalysis according to the reactivity of the different surfaces to the decomposition of PH3. Deposition on (001)Si depends on the type of nanoscopic roughness of the substrate. (c) 2010 American Vacuum Society. [DOI: 10.1116/1.3442805]