Structural characterization of gallium arsenide epitaxial layers grown on Si(001)

Abstract The nucleation and growth of undoped gallium arsenide (GaAs) epitaxial layers, grown by metallo-organic vapour-phase epitaxy (MOVPE) on Si (001) substrates, were investigated by transmission electron microscopy (TEM). The influence of growth time and thermal annealing on the initial stages of growth was mainly considered. TEM studies indicated that GaAs nucleates in the form of three-dimensional epitaxial islands on Si (001) and eventually coalesced into a continuous film as growth proceeds. Dark-field TEM studies showed that high densities of primary and tertiary twins are present in the epitaxial (001) GaAs buffer layers. These microtwins, present in the epitaxial buffer layers, are able to extend to the top surface of the subsequently grown layers and were found to be the main reason for the degradation in the surface morphology of GaAs-on-Si layers.