Using tertiary-butyl arsine as a group V precursor, GaAs epitaxial layers have been grown on both (1 1 1)A- and (1 0 0)-oriented GaAs substrates in N2 ambient using the atmospheric metalorganic chemical deposition technique. The surface morphology and optical properties of the GaAs homoepitaxial layers were studied in detail. It is found that both the surface morphologies and optical properties of GaAs layers on (1 1 1)A GaAs substrates depend much more strongly on the combination of growth temperature and V/III input molar ratio, compared to the epitaxial layers on (1 0 0) plane GaAs. The photoluminescence (PL) emission efficiency increases with increasing growth temperature in the region 550–650 °C for both (1 1 1)A and (1 0 0) GaAs epitaxial layers. At room temperature, the PL emission intensity of the (1 1 1)A GaAs epilayer grown under optimum growth conditions is 67 times as strong as that of the same run-grown (1 0 0) GaAs epilayer.