Ultra‐Steep‐Slope and High‐Stability of CuInP₂S₆/WS₂ Ferroelectric Negative Capacitor Transistors by Passivation Effect and Dual‐Gate Modulation

Abstract Ferroelectric negative capacitance transistors (Fe‐NCFETs) have emerged as a promising technology for low‐power electronics and have the potential to continue Moore's law. However, the existing 2D ferroelectric materials are predominantly sulfides or halides, which are susceptible to oxidation or hydrolysis, thereby hindering their commercial production due to concerns related to performance and stability. To address these obstacles, the authors have optimized the Fe‐NCFETs composed of 2D ferroelectric CuInP₂S₆ and semiconductor WS₂ using high‐k Al₂O₃ passivation and dual‐gate modulation strategy. With atomic layer deposition (ALD) of Al₂O₃, all‐2D Fe‐NCFETs, operated at a low driven voltage of 0.3 V, achieve much improvement in stability and performance with a high ON/OFF ratio of 10⁹ and minimum subthreshold swing (SS) of 14 mV dec⁻¹, which is attributed to the negative capacitance effect of CuInP₂S₆ and passivation effect of ALD‐Al₂O₃. The dual‐gate modulation approach is also implemented to maintain the device stability and enable the improved ON/OFF ratio from 10⁵ to 10⁸, minimum SS of 10 mV dec⁻¹, and an average SS of ≈60 mV dec⁻¹ covering more than five orders of magnitude of current. This work provides a facile and effective strategy for designing all‐2D Fe‐NCFETs with ultra‐steep SS and high stability, showing exciting potential for future low‐power electronic applications.