Femtosecond Excitation of Nonthermal Carrier Populations in GaAs Quantum Wells

Abstract

We report the first direct observation of nonthermal photoexcited carrier distributions in GaAs quantum-well structures. We present experimental studies which show that these distributions thermalize within 200 fs. In addition we are able to show that near the band edge the effect of long-range Coulomb screening on the bleaching of the two-dimensional-exciton resonances is much weaker than that of the Pauli exclusion principle.