Two-valence band electron and heat transport in monocrystalline PbTe-CdTe solid solutions with high Cd content

TL;DR

This study investigates the electronic and thermal transport properties of high-quality monocrystalline PbTe-CdTe alloys with up to 10% Cd, revealing the significant role of the heavy-hole band in hole transport and potential thermoelectric efficiency.

Contribution

It provides experimental and theoretical analysis of two-valence band transport in PbTe-CdTe alloys, highlighting the impact of Cd content on thermoelectric properties and establishing a standard for high-quality single crystals.

Findings

Heavy-hole band influences hole transport at higher Cd levels.

Pb$_{1-x}$Cd$_x$Te with 1% Cd can achieve ZT ~ 1.4 at 600 K.

Experimental data serve as a standard for PbTe-CdTe alloys up to 10% Cd.

Abstract

High quality p-type PbTe-CdTe monocrystalline alloys containing up to 10 at.$\%$ of Cd are obtained by self-selecting vapor transport method. Mid infrared photoluminescence experiments are performed to follow the variation of the fundamental energy gap as a function of Cd content. The Hall mobility, thermoelectric power, thermal conductivity and thermoelectric figure of merit parameter $ZT$ are investigated experimentally and theoretically paying particular attention to the two-valence band structure of the material. It is shown that the heavy-hole band near the $\Sigma$ point of the Brillouin zone plays an important role and is responsible for the Pb$_{1-x}$Cd$_x$Te hole transport at higher Cd-content. Our data and their description can serve as the standard for Pb$_{1-x}$Cd$_x$Te single crystals with $x$ up to 0.1. It is shown, that monocrystalline Pb$_{1-x}$Cd$_x$Te samples with relatively low Cd content of about 1 at.\% and hole concentration of the order of 10$^{20}$ cm$^{-3}$ may exhibit $ZT \approx$ 1.4 at 600 K.