Fundamental band gap and direct-indirect crossover in Ge 1-x-ySixSny alloys

J. D. Gallagher, Chi Xu, Liying Jiang, John Kouvetakis, Jose Menendez

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48 Scopus citations


The Ge-like indirect band gap of Ge1-x-ySixSn y alloys has been determined over an extended y > x range using photoluminescence spectroscopy from films grown on Ge-buffered Si substrates. It is found that the compositional dependence of this transition can be fit with a bilinear expression of the form (in eV): E ind = (0.668 ± 0.008) + (0.67 ± 0.15) x - (1.77 ± 0.16) y. These energies are significantly below the prediction from a simple linear interpolation between Si, Ge, and α-Sn, revealing a large negative bowing in the compositional dependence similar to that found earlier for direct transitions. The direct-indirect crossover boundary is found to lie along the compositional line y = (0.062 ± 0.014) + (0.76 ± 0.23)x, which in the limit x → 0 agrees with earlier results for the binary Ge1-ySny alloy.

Original languageEnglish (US)
Article number202104
JournalApplied Physics Letters
Issue number20
StatePublished - Nov 11 2013

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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