ULTRAFAST HEATING AND COOLING OF ELECTRON PLASMAS IN GAINAS ALINAS QUANTUM-WELLS AFTER INTERSUBBAND EXCITATION/

Energy exchange between nonequilibrium carriers and a two-dimensional electron plasma and subsequent carrier cooling are studied in femtosec ond pump-probe experiments. (n = 1) electrons excited to the (n = 2) c onduction subband via the midinfrared intersubband transition undergo intersubband scattering and subsequently transfer a large amount of en ergy to unexcited (n = 1) electrons resulting in a hot Fermi distribut ion within 2 ps. The observed heating rate increases with the plasma d ensity whereas the subsequent cooling proceeds within 40 ps by emissio n of optical phonons and is found to be density independent. (C) 1998 Elsevier Science Ltd. All rights reserved.