The evolution of the microstructure and morphology of metal-organic vapor-phase epitaxy-grown InAs films on (100) GaAs

The large lattice mismatch (7%) between InAs and GaAs leads to a complex microstructure with many misfit-derived defects. The dependence of the microstructure and morphology of InAs films, deposited on (100) GaAs substrates via metal-organic vapor-phase epitaxy (MOVPE), on growth parameters and the substrate miscut was studied. The InAs crystal microstructure was evaluated by X-ray diffraction rocking curves, pole figures and by cross-sectional transmission electron microscopy (TEM). At high growth temperatures and high V/III ratios, multiple tilting of the InAs crystal lattice resulted in domains misoriented by 4-7 degrees with respect to each other. Low-angle grain boundaries separating the misoriented grains were observed in cross-sectional TEM micrographs. Low growth temperatures or low V/III ratios resulted in a singly oriented InAs film aligned with the GaAs. Atomic force microscopy (AFM) was employed to determine the surface morphology of InAs thin films and uncoalesced islands. The island areal number-density decreased and island size increased with increasing growth temperature. A smoother InAs surface morphology was observed for the films deposited at a low growth temperature or low V/III ratio. The early coalescence of smaller islands resulted in a single InAs orientation in the coalesced films. The observed effects are discussed in terms of the effect of an In-rich growth environment, resulting from the low growth temperature and low V/III ratio, on the InAs growth chemistry and the strain relaxation phenomena. (c) 2006 Elsevier B.V. All rights reserved.