Homo- and hetero-epitaxial gallium arsenide (GaAs) films have been deposited on single crystalline GaAs substrates of (100) orientation and on silicon (Si) substrates of 30 off the (100) orientation by ArF excimer laser (193 nm) induced metalorganic chemical vapor deposition (MOCVD). Homoepitaxial GaAs films of good structural perfection have been deposited at 425° - 500°C, and their single crystallinity has been confirmed by transmission electron microcopy. The carrier concentration decreases with increasing AsH3/(CH3)3Ga molar ratio and with decreasing substrate temperature. The use of lower growth rate during the initial stage of deposition is necessary to obtain heteroepitaxial GaAs films on. Si substrates with good structural perfection. The transmission electron microscopic examination of GaAs films of 0.15-0.2 μm thickness deposited on Si substrates at 500°C has shown that the stacking faults were present in the GaAs films; however, there are no apparent threading dislocations in the surface region of the GaAs film. The GaAs films deposited on Si were also evaluated by the electroreflectance and Raman spectra. The electroreflectance spectra indicated that the carrier concentration distribution on the surface is uniform. The Raman spectra at different regions of the film are reproducible indicating the good quality of the deposited GaAs films.