One Nanometer HfO₂-Based Ferroelectric Tunnel Junctions on Silicon

In ferroelectric materials, spontaneous symmetry breaking leads to a switchable electric polarization, which offers significant promise for nonvolatile memories. In particular, ferroelectric tunnel junctions (FTJs) have emerged as a new resistive switching memory which exploits polarization-dependent tunnel current across a thin ferroelectric barrier. This work integrates FTJs with complementary metal-oxide-semiconductor-compatible Zr-doped HfO₂ (Zr:HfO₂) ferroelectric barriers of just 1 nm thickness, grown by atomic layer deposition on silicon. These 1 nm Zr:HfO₂ tunnel junctions exhibit large polarization-driven electroresistance (>20 000%), the largest value reported for HfO₂-based FTJs. In addition, due to just a 1 nm ferroelectric barrier, these junctions provide large tunneling current (>1 A cm⁻²) at low read voltage, orders of magnitude larger than reported thicker HfO₂-based FTJs. Therefore, this proof-of-principle demonstration provides an approach to simultaneously overcome three major drawbacks of prototypical FTJs: a Si-compatible ultrathin ferroelectric, large electroresistance, and large read current for high-speed operation.