Resonant Raman scattering in GaAs/AlAs superlattices: The role of electron state mixing

In this work, resonant Raman measurements on a short-period GaAs/AlAs superlattice are presented. Under resonant excitation, near the direct band gap, zone-edge acoustic phonons are observed. Similar scattering has been also recorded in the resonant Raman spectra of an AlₓGa_1-xAs alloy layer. We show that intervalley electron scattering is at the origin of the observed similarities. This scattering is attributed to the superlattice potential for the GaAs/AlAs superlattice, and to the potential fluctuations for the AlₓGa_1-xAs alloy. The present analysis gives a clear interpretation of the Raman scattering by zone-edge acoustic phonons in both systems. Moreover, the role of disorder is discussed in terms of an activation of folded acoustic and coupled confined-interface phonons.