Specially designed structures have been grown in the GaAs/GaAlAs/AlAs system, in order to get a spatial separation of photocreated electrons and holes and thus modify the band profile under illumination in a nonstandard way. The photoinduced electric field is measured by the Stark Shift of the probing quantum well luminescence. Fields as high as 25 kV/cm are obtained under 100 W/cm2cw illumination.