Synergy of Electrostatic and Chemical Doping to Improve the Performance of Junctionless Carbon Nanotube Tunneling Field-Effect Transistors: Ultrascaling, Energy-Efficiency, and High Switching Performance

Abstract

The low on-current and direct source-to-drain tunneling (DSDT) issues are the main drawbacks in the ultrascaled tunneling field-effect transistors based on carbon nanotube and ribbons. In this article, the performance of nanoscale junctionless carbon nanotube tunneling field-effect transistors (JL CNTTFETs) is greatly improved by using the synergy of electrostatic and chemical doping engineering. The computational investigation is conducted via a quantum simulation approach, which solves self-consistently the Poisson equation and the non-equilibrium Green’s function (NEGF) formalism in the ballistic limit. The proposed high-performance JL CNTTFET is endowed with a particular doping approach in the aim of shrinking the band-to-band tunneling (BTBT) window and dilating the direct source-to-drain tunneling window, while keeping the junctionless paradigm. The obtained improvements include the on-current, off-current, ambipolar behavior, leakage current, I60 metric, subthreshold swing, current ratio, intrinsic delay, and power-delay product. The scaling capability of the proposed design was also assessed, where greatly improved switching performance and sub-thermionic subthreshold swing were recorded by using JL CNTTFET with 5 nm gate length. Moreover, a ferroelectric-based gating approach was employed for more enhancements, where further improvements in terms of switching performance were recorded. The obtained results and the conducted quantum transport analyses indicate that the proposed improvement approach can be followed to improve similar cutting-edge ultrascaled junctionless tunnel field-effect transistors based on emerging atomically thin nanomaterials.

Leveraging negative capacitance ferroelectric materials for performance boosting of sub-10 nm graphene nanoribbon field-effect transistors: a quantum simulation study

“…In fact, the curves are drawn from the I DS -V GS characteristics by using a window having a length equal to V DD =V DS =0.3 V, where the right end denotes the oncurrent while the left end denotes the off-current. By shifting this V DD window while extracting the corresponding on-and off-state currents at each step, the curves are within reach [47][48][49]. In figure 8(a), we can see that for a shared value of I OFF , the FE-GNRFETs exhibit higher I ON and for a shared value of I ON the FE-GNRFETs provide lower I OFF , which hints at substantial improvement in terms of current ratio.…”

“…Inspecting the same figure, we can see that the FE-GNRFET with T FE =6 nm exhibits sub-60 mV dec −1 at a given I DS range. In addition, we can observe that the I 60 factor, which is the highest drain current at which the SS=60 mV dec −1 is obtained (for FETs providing sub-thermionic SS) [46,47], is recorded at 4×10 -7 A. The recorded steep subthreshold behavior is normally attributed to the FE-induced amplified gate voltage shown in figure 4, which becomes significant with t FE increasing, for this reason a speed up in terms of I DS -V GS switching is pronounced.…”

Modeling and Simulation Investigation of Ferroelectric-Based Electrostatic Doping for Tunnelling Field-Effect Transistor

“…In order to achieve reliable devices or test structures at nanoscale dimensions, it is necessary to control doping levels on silicon nanosheets and to reduce leakage power. In comparison to short-channel MOSFETs, engineering of gate work function [ 5 , 6 ], lateral channels [ 7 ], multiple gate geometry [ 8 ], homodielectric based SOI/SON FETs [ 9 ], negative capacitance transistor [ 10 , 11 ], and tunneling transistors [ 12 , 13 ] have demonstrated admirable performance. Due to the band-to-band tunneling (BTBT) mechanism, devices with steep slopes, such as Tunnel-FETs, have reduced leakage current and facilitate further scaling without degradation of performance.…”

Role of Junctionless Mode in Improving the Photosensitivity of Sub-10 nm Carbon Nanotube/Nanoribbon Field-Effect Phototransistors: Quantum Simulation, Performance Assessment, and Comparison

“…However, for CNT, graphene, and the other 2D-material-based FETs, the chemical route of doping is quite cumbersome as these nanoscale devices demand the formation of very high doping gradient–based junctions [ 25 ]. Therefore, electrostatic doping, which potentially replaces the conventional donor/acceptor dopant–based chemical doping with image charge, i.e., free-electron/hole, has been adopted for nanoscale devices [ 26 , 27 , 28 ]. The difference in the photosensitive gate and CNT/GNR work function, applied voltage, energy bandgap, trap engineering, and their interactions result in an electrostatic connection that governs the carrier density for the formation of the p-channel in the proposed phototransistor.…”