First-Principles Calculations for Enhancing the TER Effect through Resonance Band Engineering

The enhancement of tunneling electroresistance (TER) of ferroelectric tunnel junctions (FTJs) can be achieved by resonant band engineering coupled to asymmetric electrodes. Using first-principles modeling based on density functional theory, we investigate this phenomenon for FTJs that consist of asymmetric electrodes (Pt and SrRuO3) and a tunneling barrier BaTiO3, with two BaTiO3 layers substituted by BaSnO3 in the barrier. We show that in such a composite barrier, the ferroelectric polarization of BaTiO3 shifts the conduction band minimum of the BaSnO3 layers below the Fermi energy, resulting in resonant tunneling. This can be combined with the method of modulating the height of the barrier by asymmetric electrodes to enhance the TER effect. The combination of these two mechanisms in this paper enables the TER effect of the FTJ to reach 106%. The proposed resonant band engineering of FTJs can serve as a viable tool to enhance their performance for device applications.