Greatly enhanced tunneling electroresistance in ferroelectric tunnel junctions with a double barrier design

We propose that the double barrier effect can substantially enhance tunneling electroresistance (TER) in ferroelectric tunnel junctions (FTJs). We design a Pt/BaTiO3/LaAlO3/Pt/BaTiO3/LaAlO3/Pt double-barrier ferroelectric tunnel junction (DB-FTJ), effectively two identical Pt/BaTiO3/LaAlO3/Pt single-barrier FTJs (SB-FTJs) in series. Density-functional calculations yield a giant TER ratio of 2.210 × 10^6 (2.210 × 10^8%) for the DB-FTJ—at least three orders of magnitude larger than that of comparable SB-FTJs—together with an ultra-low resistance–area product (RA) of 0.093 kΩ·µm^2 in the high-conductance state. Independent control of the polarization in the two ferroelectric barriers enables four distinct resistance states, making DB-FTJs promising for multi-state memory applications.