Quantum transport in weakly coupled superlattices at low temperature

TL;DR

This paper investigates low-temperature electron transport in weakly coupled superlattices, revealing a plateau in current-voltage characteristics explained by a balance between Wannier-Stark localization and tunneling.

Contribution

A theoretical model based on scattering rates is developed to explain the low-temperature tunneling behavior and the observed I(V) plateau in weakly coupled superlattices.

Findings

I(V) curves show a plateau at low temperature.

Electron-ionized donor scattering dominates the transport.

The I(V) plateau results from competition between localization and tunneling.

Abstract

We report on the study of the electrical current flowing in weakly coupled superlattice (SL) structures under an applied electric field 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 scattering rates is developed in order to understand this behaviour, exploring the different scattering mechanisms in AlGaAs alloys. The dominant interaction in usual experimental conditions such as ours 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.