EFFICIENT INTERSUBBAND SCATTERING VIA CARRIER-CARRIER INTERACTION IN QUANTUM-WELLS

Using femtosecond resonant luminescence, we have measured the intersub band scattering fare of electrons in wide GaAs quantum wells at very l ow excitation densities. Even when the spacing between the first two e lectron subbands is smaller than the LO phonon energy, we observe that intersubband scattering is a subpicosecond process, much faster than previously measured or anticipated. Our experimental results are in pe rfect agreement with Monte Carlo calculations, which show that carrier -carrier interaction is responsible for the ultrafast transitions.