Radiative recombination of free excitons in GaAs quantum wells

Abstract

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 τ 1 (∼ 17 - 40 ps) and a slow one with a time constant τ 2 (∼ 80 - 300 ps). τ 2 is the lifetime of thermalised excitens at 10 K. τ 1 is due to two mechanisms in parallel: the radiative recombination of excitons with k u < K 0 and the scattering by acoustical phonens into non radiative exciton states (k u > k 0 and J = 2). The variation with temperature of τ 1 gives the lifetime of the excitons at k = 0, τ 0, which varies between 20 and 50 ps depending on the sample.