NMR study of native defects in PbSe

TL;DR

This study uses NMR to reveal complex native defect behavior in PbSe, showing multiple carrier components and defect states affecting its electronic properties, challenging previous simplified models.

Contribution

It provides new insights into the electronic heterogeneity and defect states in PbSe using advanced NMR analysis, revealing multiple carrier components.

Findings

Identification of three discrete carrier components in PbSe

Complex temperature dependence of relaxation pathways

Explanation of defect states affecting band gap behavior

Abstract

While each atom species in PbSe corresponds to a single crystallographic site and transport measurements reveal a single carrier density, $^{207}$Pb NMR reveals a more complicated picture than previously thought comprising three discrete homogeneous carrier components, each associated with $n$- or $p$-type carrier fractions. The origins of these fractions are discussed in terms of electronic heterogeneity of the native semiconductor. The interaction mechanism between nuclear spins and lattice vibrations via fluctuating spin-rotation interaction, applicable to heavy spin-1/2 nuclei [Phys. Rev. B 74, 214420 (2006)], does not hold. Instead, a higher-order temperature dependence dominates the relaxation pathway. Shallow acceptor states and deep level defects in the midgap explain the complex temperature dependence of the direct band gap.