Structural properties of MOVPE-grown ZnSe studied by X-ray diffractometry, atomic force microscopy and electron microscopy

ZnSe/GaAs heterostructures grown by metalorganic vapor-phase epitaxy were investigated by high-resolution X-ray diffractometry (HRXRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). The SEM and AFM images indicate structural defects in the form of pyramids on the sample surfaces for thin ZnSe layers. With increasing ZnSe layer thickness the size of pyramids generally increases. Finally, for the case of very thick ZnSe layers the pyramids develop into polycrystalline islands. X-ray diffraction measurements demonstrate the tendency of polycrystalline growth with increasing thickness of ZnSe layers. The STEM bright field images show the formation of misfit dislocations already at the ZnSe/GaAs interfaces, which are correlated with the development of pyramid-like hillocks on the ZnSe surfaces.