Resonant exciton contributions to quantum-well electroabsorption

We demonstrate that electroabsorption in shallow multiple quantum-well mate rials can be significantly affected by the presence of excitons in which th e electron or hole occupies a three-dimensional resonant state. The calcula ted and experimental absorption spectra are seen to retain a two-dimensiona l character even for photon energies above the quantum well threshold. Addi tional steplike features that appear in the high energy portion of the abso rption spectra, especially at high electric field, are further shown to be associated with the resonant exciton states transitions, Our theoretical re sults are in excellent agreement with experimental measurements on multiple quantum-well systems with small conduction band energy discontinuities. [S 0163-1829(99)11447-4].