Optical vibrational modes and electron-phonon interaction in GaAs quantum wells.

We have discovered phonons active in resonant Raman scattering from GaAs quantum well heterostructures that are actually the optical vibrations of thin ionic slab. These modes are distinguished from those of bulk GaAs by new selection rules for the polarizations of incident and scattered light. Analysis of the polarizations reveals interband deformation potential processes which are not present in bulk GaAs. These processes are a direct consequence of the reduced symmetry of the layered system.