Calculation of pseudobinary phase diagrams for the infrared detector materials (Cd,Zn)Te, (Hg,Cd)Te and (Hg,Zn)Te

Abstract

An existing method is utilized to provide a new theoretical estimate for certain II–VI pseudobinary phase diagrams. This requires no knowledge of experimental liquidus or solidus data except for the melting temperatures of the pure binary end members. In this method, the liquid is treated as a ternary regular solution and the interaction parameter can be calculated with knowledge of the electronegativities, energy of vaporization and molar volumes of the pure elements. The solid is treated as a binary regular solution where the solid interaction parameter, and therefore the enthalpy of mixing, depend only on the lattice mismatch of the pure II–VI compounds. This method is shown to work well with the Cd 1− x Zn x Te alloy but to fail with Hg 1− x Cd x Te and Hg 1− x Zn x Te. We propose here that the above method fails, in these two cases, because it gives the incorrect value for the Hg–Cd and Hg–Zn interaction parameters. An alternative way to compute these interaction parameters is proposed. With this change, we are able to calculate Hg 1− x Cd x Te and Hg 1− x Zn x Te pseudobinary phase diagrams that show improved agreement with reported experimental data.