Structure of CdTe/ZnTe superlattices

Abstract

The structure of CdTe/ZnTe superlattices has been analyzed through θ/2θ x-ray diffraction, photoluminescence, and in situ reflection high-energy electron diffraction (RHEED) measurements. Samples are found to break away from CdxZn1−xTe buffer layers as a consequence of the 6% lattice mismatch in this system. However, defect densities in these superlattices are seen to drop dramatically away from the buffer layer interface, accounting for the intense photoluminescence and high-average strain fields seen in each of our samples. Observed variations in residual strains suggest that growth conditions play a role in forming misfit defects. This could explain discrepancies with calculated values of critical thickness based on models which neglect growth conditions. Photoluminescence spectra reveal that layer-to-layer growth proceeded with single monolayer uniformity, suggesting highly reproducible growth. Our results give hope for relatively defect-free CdxZn1−xTe/CdyZn1−yTe superlattices with the potential for applications to optoelectronics offered by intense visible light emitters.