Exciton absorption saturation by phase-space filling: Influence of carrier temperature and density

We investigate the temporal evolution and the density dependence of exciton bleaching in GaAs/Al (ind x) Ga (ind 1-x) As quantum wells. We find that the carrier-induced reduction of exciton oscillator strength is not influenced by carrier cooling after creation of hot carriers with femtosecond laser pulses. Excitation density experiments suggest that either phase-space filling or Coulomb screening dominates the exciton bleaching, depending on the carrier density.