Collective and single-particle excitations in Raman scattering of multilayer δ-doped systems

We report theoretical calculations of resonant Raman cross sections via spin- and charge-density mechanisms. The theory clearly demonstrates that the sufficient conditions for the appearance in extreme resonance regime of simultaneous collective and single-particle modes in the nonuniform electron gas of multilayer δ-doped systems resides in the existence of degenerate and equally coupled intersuband excitations. A comparison between theoretical and experimental data lead us to believe that the disorder inherent to the doping process should be relevant in order to give the correct intensity between the collective and single-particle modes.