Strain tuning on Van der Waals negative capacitance transistors

Negative differential capacitance induced by the energy barrier formed by the nonlinear ferroelectric insulating layer during the phase transition in negative capacitance field effect transistors (NCFETs) can break through the fundamental thermionic limit of the metal-oxide-semiconductor field effect transistors (MOSFETs), which is set at a subthreshold swing (SS) of 60 mV/dec at room temperature for low-power switching. Strain engineering has been shown effective for modulating both intrinsic and coupled properties of ferroelectric materials. However, while the modulation of negative capacitance (NC) by strain primarily remains within theoretical predictions, there is a lack of experimental studies to explore its effect on NCFETs. This study introduces strain to NCFETs by utilizing the magnetostriction of Terfenol-D upon the applied magnetic field. Results reveal a decrease in SSmin from 43.5 mV/dec to 15.2 mV/dec with a compressive strain increase from 0 to -0.005%. Additionally, theoretical results by using time-evolving Ginzburg-Landau equations and Kirchhoff's laws demonstrate that compressive strain enhances both the amplitude and duration of transient NC in CuInP2S6, while vice versa under tensile strain. This work offers valuable insights for the design of NCFET devices.