Evidence for superradiant decay of excitons in InAs quantum sheets

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Abstract
Radiative lifetimes are measured for excitons attached to isolated (001) InAs lattice planes interspersed in bulklike GaAs. The broken translational invariance of the system provides an efficient radiative decay channel for excitons. We demonstrate that the radiative lifetime is determined by the spatial extent of areas of continuous In coverage. This dependence directly indicates the superradiant nature of the spontaneous-emission process, since the decay rate is proportional to the area over which the coherent polarization of the exciton extends.