Two mini-band model for self-sustained oscillations of the current through resonant tunneling semiconductor superlattices

TL;DR

This paper introduces a two miniband model for electron transport in semiconductor superlattices, capturing self-sustained current oscillations driven by electric field pulses and resonant tunneling, with numerical analysis of the underlying quantum dynamics.

Contribution

It develops a novel two miniband Wigner function model including scattering and tunneling, and derives balance equations to explain oscillatory current behavior in superlattices.

Findings

Self-sustained current oscillations due to electric field pulses.

Higher energy miniband remains mostly empty during oscillations.

Resonant tunneling triggers population of the higher miniband.

Abstract

A two miniband model for electron transport in semiconductor superlattices that includes scattering and interminiband tunnelling is proposed. The model is formulated in terms of Wigner functions in a basis spanned by Pauli matrices, includes electron-electron scattering in the Hartree approximation and modified Bhatnagar-Gross-Krook collision tems. For strong applied fields, balance equations for the electric field and the miniband populations are derived using a Chapman-Enskog perturbation technique. These equations are then solved numerically for a dc voltage biased superlattice. Results include self-sustained current oscillations due to repeated nucleation of electric field pulses at the injecting contact region and their motion towards the collector. Numerical reconstruction of the Wigner functions shows that the miniband with higher energy is empty during most of the oscillation period: it becomes populated only when the local electric field (corresponding to the passing pulse) is sufficiently large to trigger resonant tunneling.