X-Ray Reciprocal Space Mapping of MBE Grown HgCdTe on Alternative Substrates

X-ray reciprocal space mapping is used to yield quantitative information on strain, strain-relaxation, shear, as well as dislocation density and mosaicity in MBE-grown HgCdTe heterostructures. Triple axis x-ray diffractometry is used to obtain the data, and analysis of the isointensity contours of scattered x-ray intensity around reciprocal lattice points in HgCdTe epitaxial layers grown on (211)-oriented substrates. Three different substrates, GaSb, GaAs, and CdZnTe, are used in this investigation. The in-plane and out-of-plane lattice parameters, and strain of the HgCdTe epilayer and underlying CdTe buffer layer, are determined from x-ray reciprocal space maps about the symmetric (422), and asymmetric (333 & 511) reciprocal lattice points. Analysis of X-ray scattering about the lattice mismatched reciprocal lattice points show approximately an order of magnitude increase in shear, dislocation density, and strain for growth on alternative substrates in comparison to HgCdTe grown on lattice matched CdZnTe. HgCdTe on GaSb exhibits less shear and the layers are found to be relaxed within the buffer layer. In comparison, higher density of misfit dislocations were found in epilayers grown on GaAs. The analysis of strain distribution, and misfit dislocation density clearly indicate the potential application of GaSb as an alternative substrate for MBE growth of HgCdTe.