Optical critical points of thin-film Ge1-y Sny alloys: A comparative Ge1-y Sny Ge1-x six study

Vijay R. D'Costa, Candi S. Cook, A. G. Birdwell, Chris L. Littler, Michael Canonico, Stefan Zollner, John Kouvetakis, Jose Menendez

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Abstract

The E0, E0 + Δ0, E1, E1 + Δ1, E0′, and E2 optical transitions have been measured in Ge1-y Sny alloys (y<0.2) using spectroscopic ellipsometry and photoreflectance. The results indicate a strong nonlinearity (bowing) in the compositional dependence of these quantities. Such behavior is not predicted by electronic structure calculations within the virtual crystal approximation. The bowing parameters for Ge1-y Sny alloys show an intriguing correlation with the corresponding bowing parameters in the Ge1-x Six system, suggesting a scaling behavior for the electronic properties that is the analog of the scaling behavior found earlier for the vibrational properties. A direct consequence of this scaling behavior is a significant reduction (relative to prior theoretical estimates within the virtual crystal approximation) of the concentration yc for a crossover from an indirect- to a direct-gap system.

Original languageEnglish (US)
Article number125207
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume73
Issue number12
DOIs
StatePublished - Apr 6 2006

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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