The selective area, metalorganic vapor-phase epitaxy of gallium arsenide on silicon substrates was investigated. Low-temperature arsenic passivation of the silicon surface was realized at 650 degrees C. A two-step growth method was used to deposit the GaAs films with an optimum nucleation temperature of 400 degrees C. Layers nucleated at 350 degrees C or below were found to be polycrystalline whereas those nucleated at 400 degrees C and above were single crystal. The X-ray diffraction full-width-at-half-maximum decreased from 890 to 775 arcsec for a 1.0-mu m-thick GaAs layer grown on unpatterned versus patterned Si (100) wafers. The 77 K photoluminescence peak position was 1.489 and 1.498 eV for a 1.0-mu m-thick GaAs layer on unpatterned and patterned substrates, respectively. Based on the photoluminescence peak shift, we find that selective area growth of GaAs on Si improves film crystallinity while reducing the in plane strain in the film by 35%. (C) 2007 Elsevier B.V. All rights reserved.