Magnetic-field-enhanced Raman scattering by confined and interface phonons in semiconductor superlattices

Magnetic fields perpendicular to the layers in GaAs-${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As superlattices lead to a dramatic enhancement of Raman scattering by confined LO phonons, and also to strong ‘‘forbidden’’ backscattering by interface modes. Results are consistent with a scattering mechanism involving Fröhlich coupling to phonons with wave-vector components in the plane of the layers and photoexcited carriers which account for the breakdown in momentum conservation.