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The potential for negative-capacitance field-effect transistors (NCFETs) to enhance the unity-current-gain cutoff frequency ${f}_{T}$ and ${g}_{m}{f}_{T}/{I}_{D}$ ratio through a technique that mitigates the impacts of extrinsic parasitic capacitances is investigated, where ${g}_{m}$ is the transconductance and ${I}_{D}$ is the dc drain current and where “extrinsic” refers to elements arising outside an “intrinsic” or core transistor structure. We explain the technique and show that NCFETs can provide significant gains in extrinsic ${f}_{T}$ and ${g}_{m}{f}_{T}/{I}_{D}$ from this mitigation effect. However, an inherent degradation of intrinsic ${f}_{T}$ needs to be addressed to maximize these benefits, and this degradation can be alleviated through channel-length scaling as well as supply- and threshold-voltage tuning. The relative influences of different extrinsic parasitic elements are also evaluated, and it is found that improvements to ${f}_{T}$ and ${g}_{m}{f}_{T}/{I}_{D}$ increase as extrinsic parasitic capacitance increases and decrease as extrinsic parasitic resistance increases. Overall, this work finds that NCFET structures are promising candidates to mitigate the impacts of extrinsic parasitics in aggressively scaled transistors for the next-generation RF applications. [ABSTRACT FROM AUTHOR]

We propose a parallel negative-capacitance field-effect transistor (P-NCFET) structure, in which a ferroelectric operating in its negative-capacitance region is placed in parallel with the gate and source terminals of a MOSFET. The P-NCFET is stabilized by combining careful matching of the ferroelectric with the gate capacitance along with simple feedback realized using current mirrors. The novel stabilization approach opens the possibility for a variety of new applications that exploit the negative capacitance of ferroelectrics to cancel capacitance in integrated circuits. As an example, we show the P-NCFET structure has a significantly higher unity-current-gain frequency ${f}_{T}$ compared to a conventional MOSFET. [ABSTRACT FROM AUTHOR]

We use full quantum-transport simulations by coupling the Landau–Khalatnikov (LK) and Poisson equations self-consistently with the nonequilibrium Green’s function (NEGF) formalism, and calibrated to experimental results, to investigate extremely scaled negative-capacitance, field-effect transistors (NCFETs) having dimensions toward the end of the international roadmap for devices and systems (IRDS), that is, to sub-10-nm gate lengths, where channel transport can be expected to be governed by quantum-mechanical effects. We identify how the ferroelectric affects both thermionic emission and quantum-mechanical tunneling of electrons, both of which are relevant transport mechanisms for these ultrascaled devices. Our detailed results show that while NCFETs are not immune to the increase in the tunneling as they undergo extreme channel-length scaling, the metal–ferroelectric–insulator–semiconductor (MFIS) structure will continue to offer benefits to a subthreshold slope, ON- and OFF-currents, drain-induced barrier lowering, and output conductance until the end of the roadmap. These improvements allow MFIS NCFETs of any given node to achieve similar performance to nonferroelectric devices of the immediately preceding (higher-dimension) node. The fundamental reason for the improvements is identified to be the presence of voltage amplification at the top of the barrier (TOB) and suppression of TOB movement with drain voltage. [ABSTRACT FROM AUTHOR]

Recently, negative-capacitance FETs (NCFETs) have been proposed to reduce subthreshold slope and help continue supply-voltage scaling alongside channel-length scaling. We investigate the high-frequency switching behavior of NCFETs using the Landau–Khalatnikov equation to model ferroelectric materials. Multidomain interactions in the ferroelectric are considered, resulting in strong agreement with experimental measurements. Operation of NCFETs at gigahertz frequencies is investigated with this experimentally validated multidomain model. We find that the effectiveness of the voltage amplification in NCFETs is strongly dependent on the viscosity coefficient $\rho $ of the ferroelectric, and that a low \rho $ ( <0.1~\Omega \cdot \text {m} ) is required for the operation at the high gigahertz frequencies. [ABSTRACT FROM PUBLISHER]

Among the contenders for applications at terahertz frequencies are III–V high-electron-mobility transistors (HEMTs). In this paper, we report on a tendency for III–V devices with low effective-mass channel materials to exhibit a saturation in their unity-current-gain and unity-power-gain cutoff frequencies (f_T and f\max ) with a downscaling of gate length. We focus on InGaAs and GaN HEMTs and examine gate lengths from 50 nm down to 10 nm. A self-consistent, quantum-mechanical solver based on the method of nonequilibrium Green's functions is used to quasistatically extract the f_T for intrinsic III–V devices. This model is then combined with the series resistances of the heterostructure stack and the parasitic resistances and capacitances of the metal contacts to develop a complete extrinsic model, and to extract the extrinsic f_T and f\max . It is shown that the f_T and f\max of III–V devices will saturate, i.e., attain a maximum value that ceases to increase as the gate length is scaled down, and that the saturation is caused by the low effective mass of III–V materials. It is also shown that the InGaAs HEMTs have faster f_T at long gate lengths, but as a consequence of their lower effective mass, they experience a more rapid f_T saturation than the GaN HEMTs, such that the two devices have a comparable f_T at very short gate lengths (∼10 nm). On the other hand, due to favorable parasitics, it is shown that the InGaAs HEMTs have a higher f\max at all the gate lengths considered in this paper. [ABSTRACT FROM PUBLISHER]