Electrostatic amplification of ferroelectric tunneling in van der Waals heterostructures

Ferroelectric tunnel junctions promise energy-efficient non-volatile memories, but their scalability is limited by an electrostatic dilemma: ultrathin ferroelectric barriers enhance tunneling modulation yet suffer from severe leakage, whereas thicker barriers suppress leakage but reduce electroresistance. Here, we identify an electrostatic regime in a van der Waals heterostructure that is enabled by a low-density-of-states electrode and overcomes this trade-off by decoupling polarization control, tunneling modulation, and charge screening. Using a ferroelectric-semiconductor tunnel memory based on Bi 2 O 2 Se, hexagonal boron nitride, and graphene, we achieve ultra-low leakage and tunneling electroresistance exceeding 10 5 . Low-bias readout is dominated by polarization-modulated tunneling, while higher bias programming may involve additional field-assisted carrier redistribution. Systematic variation of graphene thickness reveals an exponential decay of electroresistance governed by Thomas-Fermi screening, establishing a screening-based design rule for van der Waals ferroelectric tunneling heterostructures.