Insights into electron transport in a ferroelectric tunnel junction

TL;DR

This paper investigates electron transport in ferroelectric tunnel junctions using the NEGF method, revealing that temperature effects involve resonance states beyond traditional mechanisms, impacting device performance.

Contribution

It introduces the NEGF approach to analyze FTJ electron tunneling, highlighting the role of resonance states and temperature effects beyond conventional models.

Findings

Resonance states significantly influence electron transmission in FTJs.

Temperature affects FTJ performance through non-trivial resonance mechanisms.

NEGF provides detailed insights into wavefunctions at resonant energies.

Abstract

The success of a ferroelectric tunnel junction (FTJ) depends on the asymmetry of electron tunneling as given by the tunneling electroresistance (TER) effect. This characteristic is mainly assessed considering three transport mechanisms: direct tunneling, thermionic emission, and Fowler-Nordheim tunneling. Here, by analyzing the effect of temperature on TER, we show that taking into account only these mechanisms may not be enough in order to fully characterize the performance of FTJ devices. We approach the electron tunneling in FTJ with the non-equilibrium Green function (NEGF) method, which is able to overcome the limitations affecting the three mechanisms mentioned above. We bring evidence that the performance of FTJs is also affected by temperature, in a non-trivial way, via resonance (Gamow-Siegert) states, which are present in the electron transmission probability and are usually situated above the barrier. Although the NEGF technique does not provide direct access to the wavefunctions, we show that, for single-band transport, one can find the wavefunction at any given energy and in particular at resonant energies in the system.