Far-infrared study of localized states in In-doped Pb0.75Sn0.25Te single crystals.

Abstract

Far-infrared reflectivity spectra of a 1.2 at. % In-doped ${\mathrm{Pb}}_{0.75}$${\mathrm{Sn}}_{0.25}$Te single crystal and galvanomagnetic data are presented. The infrared spectra were analyzed with use of a fitting procedure based on the plasmon-phonon interaction model. The plasma frequency was found to decrease at cooling from 300 to 30 K and a sharp drop in ${\mathrm{\ensuremath{\omega}}}_{\mathit{p}}$ was observed between 20 and 10 K. In addition, at T\ensuremath{\le}20 K, a new structure on the reflectivity spectra is clearly observable. It may be associated with localized states in In-doped ${\mathrm{Pb}}_{0.75}$${\mathrm{Sn}}_{0.25}$Te.