Optical critical points of thin-film Ge1ySny alloys: A comparative Ge1ySnyGe1xSix study

Vijay R. D’Costa, Candi S. Cook, A. G. Birdwell, Chris L. Littler, Michael Canonico, Stefan Zollner, John Kouvetakis, and José Menéndez
Phys. Rev. B 73, 125207 – Published 31 March 2006

Abstract

The E0, E0+Δ0, E1, E1+Δ1, E0, and E2 optical transitions have been measured in Ge1ySny 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 Ge1ySny alloys show an intriguing correlation with the corresponding bowing parameters in the Ge1xSix 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.

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  • Received 6 October 2005

DOI:https://doi.org/10.1103/PhysRevB.73.125207

©2006 American Physical Society

Authors & Affiliations

Vijay R. D’Costa1, Candi S. Cook1,2, A. G. Birdwell3, Chris L. Littler4, Michael Canonico5, Stefan Zollner6, John Kouvetakis2, and José Menéndez1

  • 1Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287-1504, USA
  • 2Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA
  • 3Semiconductor Electronics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8121, USA
  • 4Department of Physics, University of North Texas, Denton, Texas 76203, USA
  • 5Freescale Semiconductor, Physical Analysis Lab Arizona (PALAZ), 2100 E. Elliot Road, Tempe, Arizona 85284, USA
  • 6Freescale Semiconductor, APRDL, MD K10, 3501 Ed Bluestein Boulevard, Austin, Texas 78721, USA

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Vol. 73, Iss. 12 — 15 March 2006

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