Optical investigation of 2D Mott transitions in GaAs/GaAlAs quantum well structures

Abstract In transmission experiments performed under quasi-equilibrium conditions at low temperatures we investigated the bleaching of the quasi-2D excitons in GaAs/GaAlAs MQW structures with special emphasis on the behaviour of the excitons at the different subband edges. The 1hh excitons are found to be much more sensitive to bleaching than the other excitons. We attribute this to phase space filling effects which should reduce the 1hh excitonic structures additionally to the usual screening due to the long-range Coulomb interaction, which screens the excitons related to transitions between higher subbands only. We determined the 2D Mott density of the 2hh exciton performing a lineshape analysis of the luminescence of the electron-hole pairs measured simultaneously.