Ab initio studies of electronic structure of defects in PbTe

TL;DR

This study uses ab initio DFT calculations to analyze how various defects affect the electronic structure of PbTe, revealing complex modifications in density of states that influence its transport properties.

Contribution

It provides a comprehensive ab initio analysis of multiple defect types in PbTe, highlighting their impact on electronic structure and transport behavior.

Findings

Defects significantly modify the density of states near band edges.

Transport properties cannot be explained by simple doping models.

The study confirms complex defect-induced electronic effects in PbTe.

Abstract

Understanding the detailed electronic structure of deep defect states in narrow band-gap semiconductors has been a challenging problem. Recently, self-consistent ab initio calculations within density functional theory (DFT) using supercell models have been successful in tackling this problem. In this paper, we carry out such calculations in PbTe, a well-known narrow band-gap semiconductor, for a large class of defects: cationic and anionic substitutional impurities of different valence, and cationic and anionic vacancies. For the cationic defects, we study a series of compounds RPb2n-1Te2n, where R is vacancy or monovalent, divalent, or trivalent atom; for the anionic defects, we study compounds MPb2nTe2n-1, where M is vacancy, S, Se or I. We find that the density of states (DOS) near the top of the valence band and the bottom of the conduction band get significantly modified for most of these defects. This suggests that the transport properties of PbTe in the presence of impurities can not be interpreted by simple carrier doping concepts, confirming such ideas developed from qualitative and semi-quantitative arguments.