High quality InAs films are grown on GaAs (0 0 1) substrates by low-pressure metalorganic vapor phase epitaxy. It is found that the combination of InAs buffer grown under low temperature and InAs epilayer grown under high temperature is essential to obtain high quality InAs films. The role of buffer layer is discussed. AFM observation on thick InAs film surface shows that step-flow growth mode takes place. The crystalline quality of InAs is characterized by transmission electron microscopy and X-ray diffraction. The crystalline quality improves with increase in film thickness. Residual strain due to thermal mismatch between InAs layers and GaAs substrates is investigated with X-ray diffraction. (C) 2004 Elsevier B.V. All rights reserved.