Structural and electronic properties of Pb1-xCdxTe and Pb1-xMnxTe ternary alloys

TL;DR

This study uses ab initio and tight-binding methods to analyze the structural stability and electronic properties of PbTe-based ternary alloys, revealing how composition affects lattice structure and band gap, with implications for thermoelectric applications.

Contribution

It introduces new tight-binding parameterizations and provides a comprehensive theoretical analysis of structural and electronic changes in Pb1-xCdxTe and Pb1-xMnxTe alloys.

Findings

Lattice constant decreases with increasing x, matching experimental observations.

Band gap at the L point increases with x, consistent with photoluminescence data.

Enhanced thermoelectric power is predicted in p-type alloys.

Abstract

A systematic theoretical study of two PbTe-based ternary alloys, Pb1-xCdxTe and Pb1-xMnxTe, is reported. First, using ab initio methods we study the stability of the crystal structure of CdTe - PbTe solid solutions, to predict the composition for which rock-salt structure of PbTe changes into zinc-blende structure of CdTe. The dependence of the lattice parameter on Cd (Mn) content x in the mixed crystals is studied by the same methods. The obtained decrease of the lattice constant with x agrees with what is observed in both alloys. The band structures of PbTe-based ternary compounds are calculated within a tight-binding approach. To describe correctly the constituent materials new tight-binding parameterizations for PbTe and MnTe bulk crystals as well as a tight-binding description of rock-salt CdTe are proposed. For both studied ternary alloys, the calculated band gap in the L point increases with x, in qualitative agreement with photoluminescence measurements in the infrared. The results show also that in p-type Pb1-xCdxTe and Pb1-xMnxTe mixed crystals an enhancement of thermoelectrical power can be expected.