Yttrium-Doping-Induced Ferroelectric Semiconductor-to-Semimetal Phase Transition in α-In₂Se₃ van der Waals Bilayers

Two-dimensional (2D) ferroelectrics hold significant promise for pushing the scaling limits of nonvolatile memory devices. However, conventional ferroelectric tunnel junctions encounter a critical challenge in achieving concurrent optimization of low on-state resistance and a giant tunnel electroresistance (TER) ratio, constrained by the inherent limitations of the barrier regulation mechanism and significant contact resistance. These challenges lead to an intrinsic incompatibility in electrical characteristics with silicon-based standards while simultaneously posing substantial obstacles to their implementation in high-density memory integration. In this work, we propose that the yttrium-doped α-In2Se3 ferroelectric bilayer can undergo a semiconductor-to-semimetal phase transition by modulating the long-range electric dipole order with an external electric field, based on first-principle calculations. An intrinsic TER of 108% and an ultrahigh on-state current density of 1.89 mA μm–1 are achieved simultaneously at a supply voltage of 0.1 V. The electronic properties of the contacts between the InYSe3/In2Se3 bilayer and cobalt electrodes indicate that Ohmic contacts can be achieved in both opposite polarization states. Two-bit memory is demonstrated in atomic InYSe3/In2Se3/InYSe3 antiferroelectric tunnel junctions, demonstrating their potential for application in low-power and high-density nonvolatile memory.