Investigation of HgTe-HgCdTe superlattices by high-resolution x-ray diffraction

In this study, high-resolution diffraction has been used to investigate the strain state and uniformity of (001) and (112) oriented HgTe-CdTe superlattices grown by molecular beam epitaxy. A number of reciprocal space maps were taken over the surface of the grown wafer, and variations in the spread of lattice spacings and tilts were quantified and used to identify the presence of local defects. Though all growths were fully strained, those with a larger mismatch exhibited a greater spread of lattice tilts from the substrate to the superlattice layers in both orientations. Further, the variation in composition of the CdZnTe substrates resulted in a variation of strain over the surface of the superlattice, and evidence of areas of significant dislocation densities present in substrate layer corresponded with defect-rich areas in the superlattice layer.