Spectroscopic ellipsometry models of GeSn alloys at varying temperatures

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Three Ge(1-x)Snx films were measured by spectroscopic ellipsometry to extract their optical properties. The Sn contents of the films were 3.6%, 6.5%, and 8.4%, and all were fully strained to a Ge (001) substrate. Optical constants were collected from 0.39-4.116 eV, at temperatures between 78K and 475K. Resolution varied from 0.002 eV at low energies with high feature densities to 0.012 eV at high energies with low feature densities. Optical properties were extracted by modeling in J.A. Woollam’s WVASE software as three layers: a temperature-dependent Ge model from the bare wafer scans, a Ge(1-x)Snx model, and a Bruggeman effective medium approximation layer that blends the Ge(1-x)Snx model 50:50 with vacuum to account for surface roughness and any thin surface layers. WVASE .mat files are presented as tabulated and as general oscillator forms, along with plain text n and k files.