Raman scattering by coupled-layer plasmons and in-plane two-dimensional single-particle excitations in multi-quantum-well structures

Raman measurements are reported of collective modes (plasmons) and single- particle excitations in modulation-doped GaAs /Al(x)Ga(1-x)As quantum-well systems as a function of the wave-vector component k parallel to the electron layers. Samples with five layers show discrete layer-plasmon modes manifesting the coupling of the electrons in different layers by Coulomb interaction. The Raman spectra due to single-particle excitations are narrow bands peaking at a value characteristic for the response of a two-dimensional electron gas. (Author)