Inelastic Light Scattering by Two-Dimensional Electron Gas: Resonant Enhancement at the Absorption Edge of GaAs Quantum Wells

We report low temperature inelastic light scattering obtained with photon energies in resonance with the fundamental absorption edge of modulation doped GaAs-(Al0.3Ga0.7)As multiple quantum wells. We have measured spectra of single particle (spin-density) and collective (plasmons) intrasubband excitations of the high mobility two-dimensional electron gases in the GaAs quantum wells. The single particle, spin-density, excitations show resonant enhancements at the energies of the absorption edge, involving transitions from the ground (heavy) valence subband to conduction states near the Fermi level.