Resolving the On–Off Ratio Discrepancy in Bilayer 3R-MoS ₂ FeSFETs: Dual Mechanisms of Domain Wall Engineering

Bilayer 3R-MoS₂ ferroelectric semiconductor field-effect transistors (FeSFETs) commonly attributed the device's ON-OFF switching to reversible transformation between up and down polarization, without considering the electronic properties of the domain walls (DWs) in MoS₂. In this work, we use density functional theory combined with nonequilibrium Green's function methods to show that DWs formation would induce electronic reconstruction at neighboring ferroelectric domains, thereby enhancing their polarization. We also found that local compressive strain in the DW can effectively increase the local conduction band minimum, drastically suppress the OFF-state current in FeSFETs. While pristine single-domain devices exhibit ON-OFF ratios of only 6.5 (armchair) and 3.8 (zigzag) at <i>V</i>_<i>G</i> = 0 <i>V</i>, junctions incorporating DWs can yield remarkably higher ratios of 99.1 and 33.5, respectively. This work establishes that enhanced polarization and suppressed conductance due to DWs present new avenues for improving the performance of MoS₂-based FeSFETs.