Many‐Exciton Theory for Multiple Quantum‐Well Structures

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Abstract
The many‐exciton theory of highly excited semiconductors is reformulated in order to apply it to the case of a quasi two‐dimensional confinement of electrons and holes in a multiple quantum‐well structure. Using simple variational ansatzes for the exciton wave function in the low excitation limit density dependent exciton parameters are calculated for a GaAs‐GaAlAs multiple quantum‐well system. In contrast to bulk material but in agreement with experimental findings a blue shift of the excitonic resonance with increasing excitation intensity is obtained. The results are used to demonstrate nonlinear optical behaviour, especially bistabilities, for such systems.