Barrier Carbon Nanotube Field Effect Research Articles

Investigation of Parameters for Schottky Barrier (SB) Height for Schottky Barrier Based Carbon Nanotube Field Effect Transistor Device

The design and development of Schottky Barrier Carbon Nanotube Field Effect Transistor (SB CNTFET) is still in the primitive research phase for its utilization in digital design. There is an immediate requirement for the analysis of parametric relations with structural factors to benefit the researchers working in this field. This work helps in the improvement of SB based CNTFET devices to be used in the development of various circuit applications. In this work, investigation of Schottky Barrier height on the performance of SB CNTFET for various geometrical and physical design parameters at the device level has been reported. The analysis of various device parameters of carbon nanotube, i. e., chirality, diameter, band gap, oxide thickness and dielectric constant has been carried out viz. subthreshold conduction, and ION/IOFF ratio. The paper also reports the effect of high dielectric constant material in SB CNTFET with oxide thickness along with Schottky Barrier Height Variation. The performance of SB CNTFET with variation in Schottky Barrier height and temperature variation is also reported. The results obtained indicate that performance of SB based CNTFET can be modified by the proper choice of chirality, dielectrics, oxide thickness and operating temperature. The SB parameter can be optimized by proper choice of metal contact in case of CNTFET.

Suppression of Ambipolar Conduction in Schottky Barrier Carbon Nanotube Field Effect Transistors: Modeling; Optimization Using Particle Swarm Intelligence; and Fabrication

Suppression of Ambipolar Conduction in Schottky Barrier Carbon Nanotube Field Effect Transistors: Modeling; Optimization Using Particle Swarm Intelligence; and Fabrication

Design and analysis of electrostatic doped Schottky barrier CNTFET based low power SRAM

In recent years, much emphasis is given for low power memory design by reducing leakage power. Carbon nanotube field effect transistor (CNTFET) based static random access memory (SRAM) provides better stability along with low static power consumption due to variable bandgap and threshold voltage as function of diameter. Electrostatic doped Schottky barrier carbon nanotube field effect transistor (ED-SBCNTFET) accounts for much low leakage current and hence can be used for low power SRAM design. This paper proposes a novel design of ED-SBCNTFET based low power SRAM which consists of additional polarity gates. 6-T SRAM cell is designed and simulated in HSPICE for both conventional CNTFET and ED-SBCNTFET. SRAM performance is analyzed on the basis of various figures of merit i.e. stability and power dissipation. ED-SBCNTFET SRAM shows advantage of low power over conventional CNTFET SRAM without loss of stability. Furthermore, SRAM is designed for smaller diameter which gives ultra low power cell with minute change in stability. Lastly dual chirality scheme is implemented and analyzed for ED-SBCNTFET 6-T SRAM cell.

Modeling and performance analysis of Schottky barrier carbon nanotube field effect transistor SB-CNTFET

The performance of a Schottky barrier carbon nanotube field effect transistor (SB-CNTFET) has been analyzed by means of a compact model. We present a study of the physical and geometrical parameters and their effects on the static and dynamic performance of the SB-CNTFET. For the static regime, we determine the variations in the current–voltage characteristics for three values of the potential barrier and the influence of the barrier on the on-state current. Also, we report the effect of the oxide thickness on the static performance. The relationship between the current–voltage characteristics and the nanotube diameter for different values of drain–source voltage is investigated. For dynamic systems, we study the effect of the gate–source voltage, the chirality and the CNT diameter on the transition frequency. It has been observed that the performance of the SB-CNTFET can be significantly controlled by changing some physical and geometrical parameters of the device.

A Schottky Barrier CNTFET Based on Dual Material Gate Workfunction

For the first time, a schottky barrier carbon nanotube Field-Effect Transistors (SB_CNTFETs) is proposed and simulated using quantum simulation, then Comparisons are made for electrical characteristics among two SB_CNTFETs structures, which are conventional Schottky Barrier CNTFETs and Dual Material Gate Workfunction structure (DMGW structure). The results show that the Dual Material Gate Workfunction structure decreases significantly the leakage current, Increases on current, so increases on/off current ratio as well as cutoff frequency. Finally, the delay and transconductance of the two structures of SB_CNTFETs have been discussed. It is noticeable Dual Material Gate Workfunction structure has a lower delay and higher transconductance, so the Dual Material Gate Workfunction structure has a better performance compared with conventional SB_CNTFET.

Circuit Compatible Model for Electrostatic Doped Schottky Barrier CNTFET

This paper proposes a circuit compatible model for electrostatic doped Schottky barrier carbon nanotube field effect transistor (ED-SBCNTFET). The proposed model is an extension of the Schottky barrier carbon nanotube field effect transistor (SBCNTFET) to ED-SBCNTFET by adding polarity gates, which are used to create electrostatic doping. In ED-SBCNTFET, electrostatic doping is responsible for a fermi level shift of source and drain regions. A mathematical relation has been developed between fermi level shift and polarity gate bias. Both current–voltage (I–V) and capacitance–voltage (C–V) characteristics have been efficiently modeled. The results are compared with the reported semi-classical model and simulations from NanoTCAD ViDES for validation. The proposed model is much faster than numerical models as it denies self consistent equations. Finally, circuit application is demonstrated by simulating inverter using the proposed model in HSPICE.

Asymmetric lightly doped Schottky barrier CNTFET

For the first time, an asymmetric lightly doped Schottky barrier carbon nanotube field effect transistor (SB_CNTFETs) is proposed and simulated using quantum simulations. Comparisons are made among four SB_CNTFETs structures for electrical characteristics. One is the conventional SB_CNTFET with an intrinsic channel. The other proposed and studied designations are an asymmetrically doped SB_CNTFET with a doped region near the source only, a symmetrically doped source and drain SB_CNTFETand an asymmetric lightly doped SB_CNTFET which shows the ultimate performance among all. The results show that the new asymmetric lightly doped design decreases significantly the leakage current and thus increases on/off ratio as well as cutoff frequency. It is also demonstrated that this structure possesses two perceivable steps in potential profile of the channel, which lead to another lateral electric field peak inside the channel which leads to the immunity against short-channel effects. The cutoff frequency characteristics of the four structures of SB_CNTFETs have been discussed. Results show that for channel lengths >30 nm cutoff frequency of the asymmetric lightly doped SB_CNTFETis greater than others. The effect of different doped region lengths in a 30 nm SB_CNTFET has been discussed as well. The proposed new design is promising from several points of view discussed in the study.

Noise analysis of coaxial Schottky barrier carbon nanotube fets using non equilibrium Green’s function formalism

Abstract The effect of noise on the performance of Schottky Barrier Carbon Nanotube Field Effect Transistors (SB-CNTFETs) has been investigated under various bias conditions. In order to calculate the noise power spectral density, the Non-Equilibrium Green’s Function formalism (NEGF) is used to obtain the transmission coefficient and the number of carriers inside the channel. Results are presented in two sections: In the first section the Hooge’s empirical rule is used to investigate the flicker noise properties of SB-CNTFETs with defects in the gate oxide region, while in the second section the thermal and shot noise properties of SB-CNTFETs are studied. Finally, the best bias points in the ON and OFF states have been suggested according to the total noise power spectral density and the device signal to noise ratio.

Ballistic transport in Schottky barrier carbon nanotube FETs

Simulation of Schottky barrier carbon nanotube field effect transistors (SB-CNTFETs) is presented to yield the electrostatic potential, carrier concentration and current within the device. The simulator is based on a self-consistent solution of Poisson's equation and the carrier transport equation. The finite element method is used for solving Poisson's equation while the non-equilibrium Green's function formalism is used to model the carrier transport. The developed simulator is used to investigate the effects of device parameters on device performance.

Optimization of Schottky barrier carbon nanotube field effect transistors

Carbon nanotube field-effect transistors (CNTFETs) have been studied in recent years as a potential alternative to CMOS devices, because of the capability of ballistic transport. CNTFETs can be fabricated with Ohmic or Schottky type contacts. We focus here on Schottky barrier CNTFETs which operate by modulating the transmission coefficient of carriers through the Schottky barriers at the interface between the metal and the carbon nanotube (CNT). The behavior of these devices has been studied by solving the coupled Schrödinger–Poisson equation system. In agreement with experimental results, simulations indicate the ambipolar behavior of these devices. However, the ambipolar behavior limits the performance of these devices in both on and off regimes. To suppress this effect a double gate structure is proposed. Simulations demonstrate that this structure exhibits improved device characteristics.