Comprehensive analysis of short-channel effects & switching speed in CNTFETs: A 2D quantum simulation approach

Abstract

• In order to calculate the performance of the device on a nanoscale, a simulation that is based on a non-equilibrium Green's function (NEGF) is employed • From Fig. 3 we can see that Ion current is increase 57.642 % for tube diameter 1.0179 nm to 1.95575 nm for dielectric constant 3.9. The current increase 100% for dielectric constant 3.9 to 80 using 1.4877 nm of tube diameter. With increasing diameter, the level of the ON-current in the saturation zone visibly rises. • When the tube diameter is 1.95575 nm, the I ON /I OFF ratio is 7.16 × 10 5 when using dielectric constant 3.9, but it is 1.23 × 10 6 when using dielectric constant 80. The I ON /I OFF ratio nearly doubles with higher CNT tube diameter and large dielectric material content. • Higher dielectric constants (ε r = 80, Ti₂O₃) improve gate control, increase ION current, reduce SS, and mitigate DIBL, making CNTFETs more efficient for nanoelectronics applications. • CNTFETs outperform traditional MOSFETs, FinFETs, and TFETs in terms of switching ratio, lower SS (∼67 mV/decade), and lower DIBL (∼45.42 mV/V). Through the development of a two-dimensional (2D) full quantum simulation, the properties of carbon nanotube field-effect transistors (CNTFETs) at varying tube diameters and dielectric constants of CNT have been exhaustively investigated. Simulations were conducted using the self-consistent solution of 2D Poisson-Schrödinger equations within the nonequilibrium Green's function (NEGF) formalism. This paper investigates the short-channel effects on CNTFET performance using the NEGF function. The numerical model facilitates a greater understanding of the physical mechanisms at play and guides the design of CNTFETs to enhance transistor performance. This research aims to improve the efficacy of CNTFETs by enhancing device parameters and gaining a deeper understanding of CNT characteristics. The short-channel effect is a significant concern in CNTFETs as the channel length decreases. Using CNTFET mathematical modeling, we analyzed the switching speed (I ON /I OFF ) ratio and the short channel effect (SCE). We have analyzed the effects of drain-induced barrier lowering (DIBL), subthreshold swing (SS), and carrier injection velocity (V inj ) for finding the short channel effect of CNTFETs with varying tube diameters and dielectric constants. This paper also illustrates the influence of gate capacitance(C G ), output conductance (g d ), voltage gain(A V ) & transconductance (g m ) on the different parameters of the CNTFET. This comparative analysis demonstrates that a reduced transconductance corresponds to a larger bandgap, indicating a firmer control of the gate over the channel. If the channel or tube diameter is reduced, the bandgap energy will exhibit an increasing pattern, resulting in a thickening of the tunneling barrier, a reduction in the drain transconductance, and an increase in the threshold voltage, all of which will result in an increase in SS. The findings provide important insights into the short-channel behavior of CNTFETs and offer recommendations for optimizing their performance in future nanoelectronics applications. This study shows that Ion current increase 57.642 % for varying tube diameter 1.0179 nm to 1.95575 nm for dielectric constant 3.9. And the Ion current increase 100% for changing dielectric constant 3.9 to 80 using 1.4877 nm of tube diameter. At smaller tube diameters, the ION/IOFF ratio is nearly three times greater for materials with a higher dielectric constant. Also, the findings demonstrate that for lower tube diameter 1.0179 nm output conductance will increase by 50.30% & using higher tube diameter 1.95575 nm the output conductance will increase by 32.88% by varying dielectric material permittivity from 3.9 (SiO 2 ) to 80 (Ti 2 O 3 ).

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