MBE Growth of II-VI Epilayers and QW Structures on Hexagonal ZnCdS and CdSSe Substrates

Abstract

ZnTe, ZnSe layers and ZnCdTe/ZnTe, ZnCdSe/ZnSe quantum well structures were grown on hexagonal Zn 0.05 Cd 0.95 S(0001) and CdS 0.85 Se 0.15 (1120) by molecular beam epitaxy and studied by cathodoluminescence (CL), photoreflection, and X-ray diffraction. The structures grown on the (1120) substrates had rough surface while the structures grown on the (0001) substrate were mirror-like. All structures were cubic. In the ZnSe based structures, the (111) and (110) lattice directions of epilayers coincided with the (0001) and (1120) directions of CdZnS(0001) substrate, respectively. High mismatching leaded to a lattice relaxation of these epilayers by introduction of misfit dislocations. This was the reason of low CL intensity. In spite of higher mismatching, the ZnTe based epilayers grown on (0001) substrates had more perfect lattice structure and more intense CL than ZnSe based epilayers. Cubic lattice of ZnTe was found to be rotated approximately by 15° around the (111) direction coincided with the (0001) direction of the (0001) substrate. It was proposed that a geometrical lattice matching took place at epitaxy of ZnTe on the CdZnS(0001).