MoS₂ Negative‐Capacitance Field‐Effect Transistors with Subthreshold Swing below the Physics Limit

Abstract

The Boltzmann distribution of electrons induced fundamental barrier prevents subthreshold swing (SS) from less than 60 mV dec^-1 at room temperature, leading to high energy consumption of MOSFETs. Herein, it is demonstrated that an aggressive introduction of the negative capacitance (NC) effect of ferroelectrics can decisively break the fundamental limit governed by the "Boltzmann tyranny". Such MoS₂ negative-capacitance field-effect transistors (NC-FETs) with self-aligned top-gated geometry demonstrated here pull down the SS value to 42.5 mV dec^-1 , and simultaneously achieve superior performance of a transconductance of 45.5 μS μm and an on/off ratio of 4 × 10⁶ with channel length less than 100 nm. Furthermore, the inserted HfO₂ layer not only realizes a stable NC gate stack structure, but also prevents the ferroelectric P(VDF-TrFE) from fatigue with robust stability. Notably, the fabricated MoS₂ NC-FETs are distinctly different from traditional MOSFETs. The on-state current increases as the temperature decreases even down to 20 K, and the SS values exhibit nonlinear dependence with temperature due to the implementation of the ferroelectric gate stack. The NC-FETs enable fundamental applications through overcoming the Boltzmann limit in nanoelectronics and open up an avenue to low-power transistors needed for many exciting long-endurance portable consumer products.