Integration of resonant band with asymmetry in ferroelectric tunnel junctions

Abstract

We propose that the asymmetry-induced tunneling electroresistance (TER) effect in a ferroelectric tunnel junction (FTJ) could be improved by integrating a polarization-controlled resonant band. Using first-principles calculations and a quantum-mechanical tunneling model, we studied an asymmetric FTJ SrRuO3/BaTiO3/SrTiO3/SrRuO3. The resonant band is integrated into this FTJ by two atomic layers of BaSnO3 embedded in the barrier. In the elaborated FTJ SrRuO3/BaTiO3/BaSnO3/SrTiO3/SrRuO3, both resonant band and asymmetry work together. For one polarization direction, the BaSnO3 and SrTiO3 dielectric layers work together as barriers to provide considerable efficient barrier height for direct tunneling and lead to large tunneling resistance. For the opposite polarization, the BaSnO3 layer serves as a quantum well to induce resonant tunneling across the barrier and considerably reduces the tunneling resistance of the ON state. The integration of resonant band with asymmetry may provide a more efficient and applicable way to further improve the functionalities of FTJs.