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Raman analysis of Si/Ge strained-layer superlattices under hydrostatic pressure

Raman scattering was used to study optical phonons in a Si12Ge4 strained‐layer superlattice on c‐Si(001) that was subjected to hydrostatic pressure at room temperature. The change of phonon frequency with pressure, dω/dP, for the principal quasi‐confined LO mode in the Ge layers, is found to be significantly smaller than that for bulk crystalline Ge. This difference is shown to be due to the tuning of biaxial strain in the Ge layers and the pressure response of the confined mode as hydrostatic pressure is varied. Both strain and confinement make comparable contributions to dω/dP for the Ge layers in the superlattice examined here.