The importance of phase equilibrium for doping efficiency: Iodine doped PbTe

James Male, Matthias T. Agne, Anuj Goyal, Shashwat Anand, Ian T. Witting, Vladan Stevanović, G. Jeffrey Snyder*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Semiconductor engineering relies heavily on doping efficiency and dopability. Low doping efficiency may cause low mobility and failure to reach target carrier concentrations or even the desired carrier type. Semiconducting thermoelectric materials perform best with degenerate carrier concentrations, meaning high performance in new materials might not be realized experimentally without a route to optimal doping. Doping in the classic PbTe thermoelectric system has been largely successful but reported doping efficiencies can vary, raising concerns about reproducibility. Here, we stress the importance of phase equilibria considerations during synthesis to avoid undesired intrinsic defects leading to sub-optimal doping. By saturation annealing at 973 K, we decidedly fix the composition in single crystal iodine-doped PbTe samples to be Pb-rich or Te-rich without introducing impurity phases. We show that, regardless of iodine concentration, degenerate n-type carrier concentrations with ideal doping efficiency require Pb-rich compositions. Electrons in Te-rich samples are heavily compensated by charged intrinsic Pb vacancy defects. From Hall effect measurements and a simple defect model supported by modern defect calculations, we map out the 973 K ternary Pb-Te-I phase diagram to explicitly link carrier concentration and composition. Furthermore, we discuss unintentional composition changes due to loss of volatile Te during synthesis and measurements. The methods and concepts applied here may guide doping studies on other lead chalcogenide systems as well as any doped, complex semiconductor.

Original languageEnglish (US)
Pages (from-to)1444-1453
Number of pages10
JournalMaterials Horizons
Volume6
Issue number7
DOIs
StatePublished - Aug 2019

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Process Chemistry and Technology
  • Electrical and Electronic Engineering

Fingerprint

Dive into the research topics of 'The importance of phase equilibrium for doping efficiency: Iodine doped PbTe'. Together they form a unique fingerprint.

Cite this