Anisotropic defect distribution in ZnSe/ZnS epitaxial layers grown by metalorganic vapor-phase epitaxy on (001)-oriented GaAs

Epitaxial layers of ZnSe/ZnS have been grown by metalorganic vapor-phase epitaxy on (001)-oriented GaAs. A microstructural study of the defect content of these layers was performed using the combined techniques of scanning electron microscopy, reflection high-energy electron diffraction, transmission electron microscopy, and microdiffraction. Investigation of the epilayers in the [110] and [11̄0] orientations highlighted the strong anisotropy in the defect content of these ZnSe/ZnS layers. Microtwins were found exclusively in the [11̄0] sample orientation, while examination of the same layers along the orthogonal [110] projection revealed only misfit dislocations. The influence of the differential motion of α and β dislocations in the sphalerite structure is discussed in connection with these observations.