Optical band gap and the Burstein-Moss effect in iodine doped PbTe using diffuse reflectance infrared Fourier transform spectroscopy

Zachary M. Gibbs, Aaron Lalonde, G. Jeffrey Snyder*

*Corresponding author for this work

Research output: Contribution to journalArticle

111 Scopus citations

Abstract

Optical absorption edge measurements are performed on I doped PbTe using diffuse reflectance infrared Fourier transform spectroscopy. The Burstein-Moss shift, an increase in the absorption edge (optical band gap) with increasing doping level, is explored. The optical gap increases on the order of 0.1 eV for doping levels ranging from 3 × 1018 to 2 × 10 20 cm-3, relevant doping levels for good thermoelectric materials. Chemical potential is estimated from transport measurements - specifically, Hall effect and Seebeck coefficient - using a single band Kane model. In heavily doped semiconductors, it is well-known that the band gap shrinks with increasing doping level. This effect, known as band gap renormalization, is fit here using an n1/3 scaling law which reflects an electron-electron exchange interaction. The renormalization effect in these samples is shown to be more than 0.1 eV, on the same order of magnitude as the band gap itself. Existing models do not explain such large relative changes in band gap and are not entirely self-consistent. An improved theory for the renormalization in narrow gap semiconductors is required.

Original languageEnglish (US)
Article number075020
JournalNew Journal of Physics
Volume15
DOIs
StatePublished - Jul 2013

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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