Resonant quenching of exciton photoluminescence in coupled GaAs/AlAs quantum wells - effect of exciton binding energy.

We have studied the electric field dependence of the photocurrent and of the excitonic photoluminescence (PL) associated with the first and second conduction subbands in weakly coupled GaAs/AlAs quantum wells. Resonant subband alignment between adjacent QWs results in a quenching of the PL intensity from the first subband, an enhancement of the PL from the second subband, and a maximum of the photocurrent. These resonant extrema are observed at slightly different electric fields. We show that this behavior arises from the different binding energies of intra- and inter-well excitons.