Vertical transport in GaAs/AlGaAs superlattices is probed in structures with graded composition. Such structures allow both to impose a quasi electric field to the carriers and to evidence the carrier movement by the temporal changes in the luminescence line shape. The fit of this line shape by a drift‐diffusion model gives the transport properties of electrons. High mobility of the electrons is evidenced for the shortest period superlattices, in agreement with previous optical measurements. The importance of the transfer to the satellite valleys and of the finite capture time in the large well included as a marker are evidenced.