Raman study of strained Ge1−xSnx alloys

The Ge-Ge longitudinal optical Raman peak has been measured in strained Ge1−xSnx alloy layers grown on top of relaxed InyGa1−yAs buffer layers on GaAs substrates by molecular beam epitaxy. The experimental result shows that the peak frequency shift increases linearly from the value for bulk Ge with the Sn fraction x and the strain ɛ, Δω = ω − ωGe = ax + bɛ. In these experiments alloy and strain contributions are decoupled and measured separately, and a and b are determined to be a = − 82 ± 4 cm−1 and b = − 563 ± 34 cm−1, over the entire composition and strain range investigated.