INITIAL GROWTH OF GAAS ON SI(111) SUBSTRATES BY MOLECULAR-BEAM EPITAXY

We have investigated the initial growth of GaAs films on Si(111) subst rates by molecular beam epitaxy. GaAs grew while accomplishing high-qu ality grain-boundaries at a size of about 100 nm with no dislocations during the initial stage (t less than or equal to 200 nm). The high-qu ality was confirmed based on the sharpness (165 s at an as-grown thick ness of 100-200 nm) of the full width at half maximum (FWHM) of the X- ray rocking curves of (111) GaAs diffraction, and on cross-sectional t ransmission electron microscope observations. Up to a thickness of 100 nm, the FWHM coincides well with the values of a perfect crystal, cal culated based on dynamic diffraction theory. This is greatly related t o bond matching near to the interface between GaAs and Si in the (111) -orientation. However, in addition to the growth of high-quality grain boundaries, the growth accompanying areas having bad-quality regions surrounding them was dominant as the growth proceeded to thicknesses g reater than 300 nm.