Resonant Band Engineering of Ferroelectric Tunnel Junctions

TL;DR

This paper introduces a novel method of energy band engineering in ferroelectric tunnel junctions to significantly enhance tunneling electroresistance by embedding a dielectric layer with a smaller band gap, enabling polarization-controlled conductance switching.

Contribution

It demonstrates, through first-principles modeling, that embedding a BaSnO3 monolayer in BaTiO3 barriers can switch conductance states via polarization-induced band shifts, enhancing TER.

Findings

Giant ON/OFF conductance ratio achieved.

Polarization controls conduction band alignment.

Resonant tunneling significantly improves TER.

Abstract

We propose energy band engineering to enhance tunneling electroresistance (TER) in ferroelectric tunnel junctions (FTJs). We predict that an ultrathin dielectric layer with a smaller band gap, embedded into a ferroelectric barrier layer, acts as a switch controlling high and low conductance states of an FTJ depending on polarization orientation. Using first-principles modeling based on density functional theory, we investigate this phenomenon for a prototypical SrRuO3/BaTiO3/SrRuO3 FTJ with a BaSnO3 monolayer embedded in the BaTiO3 barrier. We show that in such a composite-barrier FTJ, ferroelectric polarization of BaTiO3 shifts the conduction band minimum of the BaSnO3 monolayer above or below the Fermi energy depending on polarization orientation. The resulting switching between direct and resonant tunneling leads to a TER effect with a giant ON/OFF conductance ratio. The proposed resonant band engineering of FTJs can serve as a viable tool to enhance their performance useful for device application.