The strain dependence of Ge_1−xsn_x (x = 0.083) Raman shift

We report an investigation of strain-dependent Raman frequency shift in Ge_0.917Sn_0.083 epilayer where the Sn composition is near the indirect-to-direct band gap transition point. The strain is modulated by ex-situ rapid thermal annealing and the amount of strain relaxation is determined by X-ray diffraction measurement. The results show that the Raman shift of Ge–Ge longitudinal optical phonon is linearly dependent on the in-plane strain of the GeSn layers with a coefficient b = − 299.3 cm⁻¹. Such a relationship enables characterization of GeSn epilayers using the readily accessible Raman spectroscopy. - Highlights: • We report an investigation of strain-dependent Raman shift of Ge_0.917Sn_0.083. • The strains of the films are modulated by ex-situ rapid thermal annealing. • The amount of strain is determined by X-ray diffraction. • The strain-dependent coefficient is b = − 299.3 cm⁻¹.