Temperature dependence of exciton lifetimes in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As single quantum wells

We report on continuous-wave and time-resolved measurements of the photoluminescence of good-quality single quantum wells at low temperatures (4–30 K). Luminescence arising from both free and localized excitons is observed and the influence of excitation localization on the photoluminescence decay time is investigated. Resonant pumping at the light-hole exciton transition is found to greatly increase the generation of free heavy-hole excitons. In this case, the free-exciton lifetime increases linearly with temperature (10–30 K) and the dependence of the slope on the well thickness is found to be in good quantitative agreement with the theoretical model of Andreani et al. [Solid State Commun. 77, 641 (1991)].