Critical Thickness of Exponentially and Linearly Graded HgCdTe/CdZnTe

We have investigated the glide of strain-relaxing dislocations in closely lattice matched, liquid phase epitaxially (LPE) grown, HgCdTe. A generalized LPE heterostructure was modeled based on secondary-ion mass spectroscopy (SIMS) profile measurements. Critical thickness was predicted using a force balanced method which expands upon the work recently developed by Ayers. The behavior of dislocation dynamics is predicted with respect to exponentially and linearly graded metallurgical interfaces intrinsic to the high- temperature LPE growth process. The extended Ayers model is compared against x-ray topography and cross-sectional observations of misfit dislocations by the decoration of etch pits on cleaved HgCdTe/CdZnTe. The model predicts that, for bulk Cd/Zn compositions which are nearly lattice matched, the Zn compositional profile plays an important role in determining both the onset and distribution of misfit dislocations.