Full-Wafer Strain and Relaxation Mapping of Hg1−xCdxTe Multilayer Structures Grown on Cd1−yZnyTe Substrates

Abstract

State-of-the-art Hg1−xCdxTe multilayer structures grown by molecular beam epitaxy on (211)-oriented Cd1−yZnyTe substrates have been characterized and their strain and relaxation analyzed. Techniques for measuring lattice mismatch, strain, and crystal quality by measuring symmetric and asymmetric diffraction profiles in different azimuths were adapted and performed in combination with dislocation delineation for full-wafer and multilayer characterization. It was found that the degree of lattice mismatch and in turn the strain state of epitaxial multilayers can be made uniform across full wafers in optimized structures. A strong correlation was revealed between the Zn composition of the Cd1−yZnyTe substrates and the crystal quality of the active layers in the multilayer structures. This method can be generalized to optimize multilayer structures to minimize relaxation by the generation of extended defects.