EXCITONIC PROPERTIES OF WEAKLY COUPLED GAAS SINGLE QUANTUM-WELLS INVESTIGATED WITH HIGH-RESOLUTION PHOTOLUMINESCENCE EXCITATION SPECTROSCOPY

Photoluminescence spectra of three weakly coupled GaAs quantum wells a re measured as a function of the excitation energy with a high resolut ion of both the excitation and the detection energy. The spectra exhib it fine structures corresponding to island terraces as well as superfi ne structures associated with the coexistence of free and bound excito ns. We present direct evidence for the transfer of carriers, excitons or exciton energy between the growth islands of the same well and adja cent wells. The relative occupation of free and bound exciton states d epends strongly on temperature, carrier density, and excitation energy . A qualitative model, which explains these experimental results as a consequence of interwell interaction of excitons, is suggested.