Luminescence and intersubband excitations in high-density two-dimensional electron gases

We report a detailed analysis of both luminescence and electronic Raman-scattering results in modulation-doped single quantum wells. Wave-vector nonconservation in the electron-hole recombination process is demonstrated in these highly doped systems. We also observe, in both polarizations, surprisingly intense Raman lines in addition to the collective excitations of the electron gas. The single-particle character of these lines is proved from the analysis of their dispersion and line shape as a function of the Raman in-plane wave vector.