Raman scattering by acoustic phonons in Fibonacci GaAs-AIAs superlattices

We report on resonant and nonresonant Raman scattering by acoustic phonons in Fibonacci GaAs-AIAs superlattices. Spectra off resonance are dominated by doublets centered at frequencies that follow a power-law behavior, in good agreement with numerical calculations based on a continuum model. Resonant data show a weighted density of states revealing the expected rich structure of gaps in the phonon spectrum. It is proposed that the electronic excitation involved in the resonant process is an intrinsic surface state of the superlattice.