Structure of hexagonal and cubic CdS heteroepitaxial layers on GaAs studied by transmission electron microscopy

The initial heteroepitaxial growth and structure of thin CdS layers on GaAs has been studied by conventional and high-resolution transmission electron microscopy. The work highlights the dependence of CdS crystal type on GaAs substrate orientation. Wurtzite-structure CdS is formed on (111)A GaAs and it is found to relieve misfit stresses by the introduction of interfacial defects, often associated with steps at the interface. Sphalerite-structure CdS is produced by initial growth on (001)GaAs and, in this case, misfit stresses are more slowly relieved, first with the formation of an asymmetrical array of interfacial dislocations and inclined stacking faults.