Resonant Raman scattering in GaAs/AlAs superlattices under electric fields.

We report an experimental study of resonant Raman scattering by confined LO and interface phonons in GaAs/AlAs superlattices under electric fields. Application of a field along the growth direction leads to a significant decrease in the Raman intensity of the even confined phonons, along with an increase in the intensities of the interface modes and the emergence of normally forbidden TO features in the spectra. We find good agreement between our measurements and a calculation of the Fr\"ohlich interaction using excitonic intermediate states, which are modified by the field due to the quantum-confined-Stark effect. We consider both a simple, phonon-only scattering mechanism, as well as interface-roughness-assisted phonon scattering and conclude that only the latter can explain our measurements.