STRUCTURAL-PROPERTIES OF ZNSE FILMS GROWN BY MIGRATION ENHANCED EPITAXY

We describe the structural properties of ZnSe grown on (001) GaAs by migration enhanced epitaxy, and show that the heterointerface plays a significant role in determining the structural properties of the ZnSe films. Films were grown with thicknesses ranging from 900 to 10 000 angstrom. Transmission electron microscopy and high-resolution x-ray diffraction measurements show that the resulting structure is highly dependent on how growth is initiated. Nearly perfect films are obtained, for thicknesses up to about 2500 angstrom [considerably thicker than the critical thickness for molecular beam epitaxy (MBE)-grown films], when growth begins with an initial exposure of the GaAs substrate to Zn. However, if growth begins with an initial high-temperature Se exposure, then stacking fault densities are greatly increased, and more rapid relaxation occurs. Comparison to MBE-grown films shows greater defect densities and a faster rate of relaxation of the misfit strain for the MBE-grown films.