Above-bandgap optical properties of biaxially strained GeSn alloys grown by molecular beam epitaxy

摘要

The complex dielectric function of biaxially strained Ge_(1-x)Sn_x (0≤x≤0.17) alloys grown on Ge (100) has been determined by spectroscopic ellipsometry from 1.2 to 4.7 eV. The effect of substitutional Sn incorporation and the epitaxial strain on the energy transitions E_1, E_1`+ Δ_1 E_0', and E_2 of GeSn alloys is investigated. Our results indicate that the strained GeSn alloys show Ge-like electronic bandstructure with all the transitions shifted downward due to the alloying of Sn. The strain dependence of E_1 and E_1 + Δ_1 transitions is explained using the deformation potential theory, and values of -5.4 ± 0.4eV and 3.8 ± 0.5 eV are obtained for the hydrostatic and shear deformation potentials, respectively.