Optical Properties of Some Pb1xSnxTe Alloys Determined from Infrared Plasma Reflectivity Measurements

Gaston Dionne and John C. Woolley
Phys. Rev. B 6, 3898 – Published 15 November 1972
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Abstract

The infrared reflectivity was measured as a function of hole concentration at 82 °K for Pb1xSnxTe alloy samples with x=0.06 and 0.21 and as a function of temperature for one sample with x=0.21 and hole concentration 8.7×1018 cm3. The measured reflectivity spectra were remarkably well fitted by the classical free-carrier dispersion relations. The optical dielectric constant ε, the susceptibility effective mass ms, and the optical mobility μopt were determined from a curve-fitting technique and a minimum-reflectivity technique generalized to include the effect of nondegeneracy. Using the former technique, a second valence-band maximum situated at about 0.23 eV below the main valence-band maximum was detected in the alloy with x=0.21. The energy gap and ε were found to be related by lnEG=0.086ε+1.65 in lead-rich Pb1xSnxTe alloys. The optical mobility was found to be about a factor of 2 lower than the conductivity mobility in all samples measured. The experimental values of ms were compared with those expected from the Kane, Cohen, and Dimmock models. The results of these comparisons indicate that the two-band models of Kane and Cohen, especially the former, are more suitable than the six-band model of Dimmock to explain the carrier-concentration dependence of ms, and that none of the models account for the large increase of ms with temperature.

  • Received 25 April 1972

DOI:https://doi.org/10.1103/PhysRevB.6.3898

©1972 American Physical Society

Authors & Affiliations

Gaston Dionne

  • Hydro-Québec Institute of Research, Varennes, Québec, Canada

John C. Woolley

  • University of Ottawa, Ottawa, Ontario, Canada

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Issue

Vol. 6, Iss. 10 — 15 November 1972

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