Optical detection of an electric field in a GaAs/AlGaAs $n{-}i{-}n$ heterostructure with double quantum wells

Processes occurring when a static transverse electric field is applied to a GaAs/AlGaAs $n{-}i{-}n$ heterostructure with single quantum wells and asymmetric tunnel-coupled double quantum wells have been investigated by optical methods. The difference between the energies of exciton transitions for quantum wells of different widths makes it possible to attribute the observed photoluminescence peaks to particular pairs of wells or particular single quantum wells. The local electric field for each quantum well has been determined in terms of the Stark shift and splitting of exciton lines in a wide range of external voltage. A qualitative model has been proposed to explain the nonmonotonic distribution of the electric field over the depth of the heterostructure.