Consequences of thermalization on the photoluminescence dynamics of shallow quantum well heterostructures

We calculate the time-resolved photoluminescence signal of a thermalized population of excitons in quantum wells. The excitons are assumed to be in thermal equilibrium with free carriers either in the well or in the barrier. The results of our calculations based on rate equations for particle and energy losses are compared to experimental data on GaAs/Ga1−xAlxAs shallow quantum wells with Al concentration varying between 1.5 and 17.8%. These structures are shown to be particularly sensitive to thermalization effects over different subbands, to such an extent that the time decay of their excitonic photoluminescence has very little to do with the true exciton radiative lifetime.