Oriented overgrowths in MOVPE-grown GaAs

The crystallographic structure of crater-containing oriented overgrowths on GaAs epitaxial layers grown by metalorganic vapor phase epitaxy (MOVPE) has been studied by transmission electron microscopy and diffraction. The craters are the visible outward sign of polycrystalline constructions of 6 grains or more having low order twin relations with the matrix. Anisotropic development of the facets of the grains is proposed to be the growth mechanism of the hillock. Stacking fault pyramids are present but their correlation with craters and overgrowths is not systematic.