Shear deformation and strain relaxation in HgCdTe on (211) CdZnTe

Shear strain is present in Hg0.68Cd0.32Te epitaxial layers grown by molecul ar beam epitaxy on (211)-oriented Cd1-yZnyTe substrates. Differences in the substrate zinc composition led to lattice mismatch between the epitaxial l ayer and the substrate. The shear strain induced by the mismatch was measur ed using reciprocal space maps in the symmetric (422) and asymmetric (511) and (333) reflections. In addition, strain relaxation through the formation of misfit dislocations was confirmed using double crystal x-ray topography . Both the shear strain and the misfit dislocation density increased with i ncreasing mismatch between the epitaxial layer and the substrate. Lattice-m atched layers were free of misfit dislocations and exhibited triple axis di ffraction rocking curve widths of approximately 6 arcsec. The combination o f a thick epitaxial layer, a low index substrate, and the potential for lat tice mismatch indicates that both shear strains and misfit dislocations mus t be considered in the structural analysis of HgCdTe/CdZnTe heterostructure s.