The design of asymmetric tunneling barriers in ultrathin ferroelectric tunnel junctions (FTJ) using two-dimensional (2D) materials is crucial for realizing large on:off ratios in miniaturized nonvolatile memory devices. This work investigates the impact of the contact interlayer on device performance in 2D FTJs based on van der Waals heterostructures composed of ferroelectric and 2D transition-metal dichalcogenides as contact interlayers. First-principles quantum transport simulations reveal that the contact interlayer creates asymmetric charge screening in the contact electrodes, enabling effective modulation of the tunneling barrier through ferroelectric polarization switching. A giant tunneling electroresistance ratio reaching 8 × ${10}^7$% is achieved in FTJ devices incorporating ${\mathrm{Sn}\mathrm{Se}}_2$ and doped ${\mathrm{Mo}\mathrm{S}}_2$ contact interlayers, attributed to their highly tunable band alignment with α-${\mathrm{In}}_2{\mathrm{Se}}_3$. The results also indicate that doping of the contact interlayer effectively modulates the screening of the asymmetric contact and significantly alters the tunneling barrier, offering a practical approach to enhancing FTJ performance via interface charge engineering.

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• Band gap
• Electric polarization
• Ferroelectricity
• Local density of states
• Tunneling electroresistance
• 2-dimensional systems
• Heterostructures