Abstract

We report time-resolved photoluminescence (TRPL) measurements of the radiative lifetime (τ_r) at 1.8K of resonantly excited heavy-hole excitons in a 27nm GaAs single quantum well as a function of exciton density. By the use of AlAs interface smoothing layers [1], the sample exhibits very little inhomogeneous broadening (≈0.15meV). The exciton centre of mass motion is therefore not significantly restricted by localisation in well width fluctuation islands. However, measurements of the exciton homogeneous linewidth (Γ_h) using time-resolved degenerate four wave mixing in the self-diffraction configuration (Fig.1) [2], additionally show that the sample imperfection scattering contribution to the Γ_h of these delocalised excitons is also small (0.2meV). Thus, as indicated by the dependence of Γ_h on exciton density (N_x), even at moderate exciton densities, exciton-exciton scattering is the dominant dephasing interaction within the photocreated exciton ensemble.

© 1992 The Author(s)