Ferroelectric Field-Effect Transistors Based on MoS₂ and CuInP₂S₆ Two-Dimensional van der Waals Heterostructure

We demonstrate room-temperature ferroelectric field-effect transistors (Fe-FETs) with MoS₂ and CuInP₂S₆ two-dimensional (2D) van der Waals heterostructure. The ferroelectric CuInP₂S₆ is a 2D ferroelectric insulator, integrated on top of MoS₂ channel providing a 2D/2D semiconductor/insulator interface without dangling bonds. The MoS₂- and CuInP₂S₆-based 2D van der Waals heterostructure Fe-FETs exhibit a clear counterclockwise hysteresis loop in transfer characteristics, demonstrating their ferroelectric properties. This stable nonvolatile memory property can also be modulated by the back-gate bias of the MoS₂ transistors because of the tuning of capacitance matching between the MoS₂ channel and the ferroelectric CuInP₂S₆, leading to the enhancement of the on/off current ratio. Meanwhile, the CuInP₂S₆ thin film also shows resistive switching characteristics with more than four orders of on/off ratio between low- and high-resistance states, which is also promising for resistive random-access memory applications.