Second-order Raman scattering by confined optical phonons and interface vibrational modes in GaAs-AlAs superlattices

The second-order Raman spectrum of the confined GaAs-like optical phonons in a GaAs-AlAs superlattice is reported. For laser energies in resonance with the first exciton in the GaAs quantum wells, the experiments show a series of sharp peaks that can be attributed to combinations of confined phonons of $A_1$ symmetry. An additional broader peak corresponds to the combination of the GaAs-like and AlAs-like interface vibrational modes previously reported in the first-order spectra. The resonance profile of the overtones and combinations of confined phonons is also presented.