Photochemical vapor deposition (PCVD) of GaAs on fused silica, silicon and GaAs substrates is reported here. A 1000 watt Hg-Xe arc lamp is utilized as the light source with arsine and triethylgallium serving as the reactants. Epitaxial film growth is shown to occur for deposition on both GaAs and silicon substrates. These thin films are characterized using Auger electron spectroscopy, energy dispersive spectrometry, scanning electron microscopy and x-ray diffraction. The results of this study demonstrate the effectiveness in utilizing both photolysis and pyrolysis to achieve deposition.