INITIAL-STAGES OF MOVPE GROWTH OF GAAS ON SI(001) AND SI(111)

The nucleation and growth of undoped gallium arsenide (GaAs) epitaxial layers, grown by metalorganic vapour phase epitaxy (MOVPE) on Si(001) and Si(111) substrates, were investigated by transmission electron microscopy (TEM). It was found, on both (001) and (111) silicon substrate orientations, that GaAs nucleated in the form of three-dimensional epitaxial islands. However, the initial island densities on Si(001) were a factor of two higher than on Si(111). As growth proceeded, these islands eventually coalesced into a continuous epitaxial film. Dark-field TEM studies showed that a high density of microtwins was present in the continuous epitaxial GaAs layers grown on silicon.