Excitons in InAs/GaAs submonolayer quantum wells

We show that the optical response of excitons localized at single InAs monolayers in a GaAs matrix is determined by the two-dimensional nature of the plane potential. The single InAs monolayer acts as a generalized quantum well despite the fact that the binding energy as well as the spatial extent of the localized excitons are bulklike. This demonstrates the fundamental role of the dimensionality of the center-of-mass motion of excitons for their optical response.