Giant Tunneling Electroresistance and Anisotropic Photoresponse in Sliding Ferroelectric Homojunctions Based on Bilayer Janus MoSSe.

Interlayer-sliding ferroelectricity in van der Waals bilayers enables ultralow-power switching, but practical devices are often limited by contact/interface scattering and weak coupling between polarization and transport. We propose homophase lateral architectures based on bilayer Janus MoSSe: a 1T/2H/1T ferroelectric tunnel homojunction and an H-phase lateral p-i-n photodetector (artificially doped electrode). Metallic 1T electrodes largely eliminate contact barriers and maximize polarization-driven tunneling modulation. Using non-equilibrium Green's function-density functional theory (Perdew-Burke-Ernzerhof approximation, without explicit spin-orbit coupling), we find that AB to BA sliding reduces the current from the nA range to the pA range, with the minimum current of|IOFF|min = 2.83 pA, yielding giant tunneling electroresistance up to 5.3 × 104%. Projected local density of states reveals a non-rigid long-range potential redistribution that reshapes the tunneling barrier and opens high-transmission channels. In the p-i-n photodetector, the response is strongly anisotropic and stacking-dependent: AB reaches photocurrent density Jph ≈ 7.2 µA·mm-2 at 2.6 eV for in-plane light versus ≈ 2.9 µA·mm-2 at 3.5 eV for out-of-plane, and exceeds BA by 1.5-1.8 times due to density of states advantages and Mo-d orbital selection rules. Bilayer Janus MoSSe therefore provides a reconfigurable platform for high-contrast memory and polarization-sensitive photodetection.