MICROSTRUCTURE AND PSEUDOMORPHISM IN MOLECULAR-BEAM EPITAXIALLY GROWNZNCDS ON GAAS(001)

We have carried out an electron-microscopy-based microstructural study of molecular beam epitaxially grown ZnxCd1-xS epilayers on GaAs(001) substrates. We find that sulfur attacks bare GaAs substrates, resultin g in pits that act as nucleating centers for defects that propagate in to the epilayer. Such pitting may be avoided by capping the GaAs subst rate with a ZnSe buffer in a sulfur-free separate growth chamber. We a lso investigate the pseudomorphic zinc blende to wurtzite crystal stru cture change in epitaxial ZnxCd1-xS and propose a microstructural mode l for this structural transition.