Quenching of miniband transport in biased undoped superlattices

The application of an electric field on a superlattice leads to a localization of the electron wave functions. We present a study on electric field dependent transport in superlattice minibands using the technique of hot electron spectroscopy. A three-terminal device is used to inject an energy tunable electron beam into a biased superlattice. The transfer ratio is measured at 4.2 K as a function of injection energy at different superlattice bias conditions. A significant decrease of the miniband transmission with increasing electric field is observed and compared to the results of a calculation based on a transfer matrix method. At about 4 kV/cm (Delta = eFNd = 0.6) the miniband current disappears. The transfer characteristics and the shift, of the superlattice states show good agreement to the theoretical results.