Electroresistance effects in ferroelectric tunnel barriers

TL;DR

This paper models electron transport in ferroelectric tunnel barriers, showing how polarization switching influences electroresistance through different tunneling mechanisms and highlighting the importance of electrode properties for device optimization.

Contribution

It introduces a comprehensive model considering multiple transport mechanisms and polarization effects, emphasizing electrode properties' role in electroresistance enhancement.

Findings

Large electroresistance in thicker ferroelectric films.

Switching transport mechanisms yields significant electroresistance.

Electrode properties critically influence device performance.

Abstract

Electron transport through fully depleted ferroelectric tunnel barriers sandwiched between two metal electrodes and its dependence on ferroelectric polarization direction are investigated. The model assumes a polarization direction dependent ferroelectric barrier. The transport mechanisms, including direct tunneling, Fowler-Nordheim tunneling and thermionic injection, are considered in the calculation of the electroresistance as a function of ferroelectric barrier properties, given by the properties of the ferroelectric, the barrier thickness, and the metal properties, and in turn of the polarization direction. Large electroresistance is favored in thicker films for all three transport mechanisms but on the expense of current density. However, switching between two transport mechanisms, i.e., direct tunneling and Fowler-Nordheim tunneling, by polarization switching yields a large electroresistance. Furthermore, the most versatile playground in optimizing the device performance was found to be the electrode properties, especially screening length and band offset with the ferroelectric.