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Electron transport in ferroelectric tunnel junctions (FTJs) with a three-step-like barrier combining a dielectric, ferromagnetic, and ferroelectric was investigated theoretically. A significant enhanced tunneling electroresistance effect was observed as compared to traditional FTJs with a bilayer composite barrier. The spin polarization also could be enhanced in a certain orientation of ferroelectric polarization. A metal/dielectric/ferromagnetic/ferroelectric/metal FTJ with a large ferromagnetic thickness is preferred for the optimal performance. The ferroelectricity in the ferroelectric layer has a weak modulation effect on the spin polarization. This work provides a way to enhance the performance of FTJs and/or to control the spin-polarized electronic transport by structure engineering. [ABSTRACT FROM AUTHOR]

Tunneling behaviors of composite ferroelectric tunnel junctions (FTJs) with a no-polar dielectric (DE) layer thickness from 1 to 4 nm were investigated. It is found that the low-resistance state (ON state) current decreases with the DE thickness, while the high-resistance state (OFF state) current decreases first and then increases. The largest tunneling electroresistance (TER) effect is observed for the 3 nm-thick DE layer, which corresponds to the lowest OFF-state current. Studies on the electron transport mechanisms show that direct tunneling dominates the ON-state tunneling behaviors for all FTJs as well as the OFF state for the thinnest DE layer of 1 nm. While Fowler–Nordheim (FN) tunneling plays a significant role in the OFF-state electron transport for thicker DE thicknesses and reinforces its role with the increasing DE thickness, the weak FN tunneling-assisted low OFF-state current for the 3 nm-thick DE layer relative to the DE layer of 4 nm contributes to the largest TER effect. [ABSTRACT FROM AUTHOR]