Ferroelectric Tunnel Junctions based on Polar-Stacked Boron Nitride

Hexagonal boron nitride (hBN), a prototypical van der Waals insulator, has recently emerged as a promising two-dimensional ferroelectric compound when assembled in a specific polar stacking. In this work, we investigate ferroelectric tunnel junctions (FTJs) made of a polar hBN bilayer sandwiched between two graphite electrodes with varied electron or hole doping. Using first-principles electronic structure and transport calculations within the nonequilibrium Green’s-function framework, we explore the effect of doping on the tunneling electroresistance effect (TER)—a change in resistance of an FTJ in response to polarization switching of ferroelectric tunnel barrier. We find that electronic and transport properties of FTJs are affected by interface terminations and atomic registries, which determine the electrostatic discontinuity at the interfaces as well as band alignment. Graphite doping alters the electrode screening length and governs the depolarization field within the barrier layer, affecting the tunneling barrier profile and its change when the electric polarization of hBN is switched between opposite directions. Our results demonstrate that the TER effect strongly depends on disproportionality of doping of the two electrodes and can be giant at certain doping concentrations. Our findings position polar hBN in combination with graphite electrodes as a model system to realize non-volatile quantum tunneling devices.