MICROSTRUCTURE AND PSEUDOMORPHISM IN MOLECULAR-BEAM EPITAXIALLY GROWN ZNCDS 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, resulting in pits that act as nucleating centers for defects that propagate into the epilayer. Such pitting may be avoided by capping the GaAs substrate with a ZnSe buffer in a sulfur-free separate growth chamber. We also investigate the pseudomorphic zinc blende to wurtzite crystal structure change in epitaxial ZnxCd1-xS and propose a microstructural model for this structural transition.