Delocalized excitons in semiconductor heterostructures

A delocalized exciton state is revealed by resonant Raman scattering in GaAs-AlGaAs multiple-quantum-well heterostructures where only lower energy, confined quasi-two-dimensional excitons had previously been observed. In spite of its extension across the abrupt GaAs-AlGaAs interface, the delocalized exciton remains a well-defined state inhomogeneously broadened to widths between 6 and 14 meV. We estimate an exciton binding energy greater than 2 meV. Scattering of the delocalized state by the exciton-optical phonon interaction results in transitions to both delocalized and quasi-two-dimensional localized excitons.