Resonance-induced delocalization of electrons in GaAs-AlAs superlattices

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Abstract
We report on novel interaction phenomena between different Stark ladders in a strongly coupled GaAs-AlAs superlattice. We observe an anticrossing behaviour between certain exciton states if the electric field perpendicular to the layers of the superlattice is such that the energy spacing between the lowest two concuction subbands is an integer multiple of the Stark-ladder spacing. This anticrossing is accompanied by a spatial delocalization of the electron states and can therefore be resolved by photocurrent spectroscopy. Our experimental results are confirmed by a numerical calculation of the field dependence of the conduction subband energies