High density two-dimensional electron-hole plasmas in quantising magnetic fields

Luminescence spectra of highly excited undoped GaAs/GaAlAs quantum wells subjected to quantising magnetic field are analysed and compared with conventional photoluminescence excitation (quasi-absorption) measurements. Transitions observed in emission show very little change in the energy position when the excitation intensity, i.e. the quasi-equilibrium population of electron-hole pairs, is varied over a wide range. These transition are, however, very different from magnetoexciton transitions seen in absorption-type spectra. The results are in contradiction with a standard model of two interpenetrating Fermi fluids, usually applied to describe the luminescence spectra of highly excited semiconductors. They indicate the importance of individual electron-hole correlations (excitonic effects) in the case of systems with quasi-discrete one-particle energy levels.