RADIATIVE RECOMBINATION OF FREE-EXCITONS IN GAAS QUANTUM-WELLS

We have measured the radiative lifetime of excitons in GaAs quantum wells under resonant excitation at 10 K using time resolved luminescence spectroscopy with 6 ps time resolution. The luminescence decay has two components: a fast one with a time constant τ1 (∼ 17 - 40 ps) and a slow one with a time constant τ2 (∼ 80 - 300 ps). τ2 is the lifetime of thermalised excitens at 10 K. τ1 is due to two mechanisms in parallel: the radiative recombination of excitons with ku < K0 and the scattering by acoustical phonens into non radiative exciton states (ku > k0 and J = 2). The variation with temperature of τ1 gives the lifetime of the excitons at k = 0, τ0, which varies between 20 and 50 ps depending on the sample. © 1993 Academic Press. All rights reserved.