Studies on the homoepitaxial growth of unintentionally doped GaAs by atmospheric pressure organometallic chemical vapor deposition using triethylarsenic and trimethylgallium have been carried out, and the effects of growth temperature, V/III ratio, and flow rate on film characteristics are reported. Mirrorlike epitaxial layers ofn‐type GaAs were obtained at substrate temperatures of 540–650 °C and at V/III ratios of 6.7–11. The carrier concentrations for these films were approximately 1016–1017cm−3, and from secondary ion mass spectroscopic analysis, the predominant epilayer impurities were determined to be both carbon and silicon.