Quantum transport in weakly coupled superlattices at low temperature

Abstract

We report on the study of the electrical current flowing through weakly coupled superlattice structures under an applied electric field and at very low temperature, i.e., in the tunneling regime. This low-temperature transport is characterized by an extremely low tunneling probability between adjacent wells. Experimentally, $I(V)$ curves at low temperature display a striking feature, i.e., a plateau or null differential conductance. A theoretical model based on the evaluation of the scattering rates is developed in order to understand this behavior, exploring the different scattering mechanisms in AlGaAs alloys. The dominant interaction in our typical operating conditions is found to be the electron-ionized donors scattering. The existence of the plateau in the $I(V)$ characteristics is physically explained by a competition between the electric field localization of the Wannier-Stark electron states in the weakly coupled quantum wells and the electric field assisted tunneling between adjacent wells. The influence of the doping concentration and profile as well as the presence of impurities inside the barrier are discussed.