Department of Electrical and Electronics Engineering
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Item A Compact Model of Gate Capacitance in Ballistic Gate-All-Around Carbon Nanotube Field Effect Transistors(MERC, 2021) Gupta, NavneetThis paper presents a one-dimensional analytical model for calculating gate capacitance in Gate-All-Around Carbon Nanotube Field Effect Transistor (GAA-CNFET) using electrostatic approach. The proposed model is inspired by the fact that quantum capacitance appears for the Carbon Nanotube (CNT) which has a low density of states. The gate capacitance is a series combination of dielectric capacitance and quantum capacitance. The model so obtained depends on the density of states (DOS), surface potential of CNT, gate voltage and diameter of CNT. The quantum capacitance obtained using developed analytical model is 2.84 pF/cm for (19, 0) CNT, which is very close to the reported value 2.54 pF/cm. While, the gate capacitance comes out to be 24.3×10-2 pF/cm. Further, the effects of dielectric thickness and diameter of CNT on the gate capacitance are also analysed. It was found that as we reduce the thickness of dielectric layer, the gate capacitance increases very marginally which provides better gate control upon the channel. The close match between the calculated and simulated results confirms the validity of the proposed model.Item Ab Initio Study of Carbon Nanotube Field Effect Transistor Gas Sensor for Detection of Ammonia and Nitrogen Dioxide Gas(IEEE, 2022-07) Gupta, Navneet; Chaturvedi, NitinLebel-free sensors are capable for sensing low concentration of gas molecules. In this article, the importance of Carbon Nanotube Field Effect Transistor (CNFET) is described for gas sensing application. The first principal study to investigate the CNFET to detection of low concentration of ammonia (NH 3 ) and nitrogen dioxide (NO 2 ) gas molecules. By discussing the electronic and transport properties of CNFET, we find that CNFET can be used for gas sensing applications. Detailed analysis of binding energy, e-k diagram, density of state (DOS), device density of state (DDOS), transmission pathways and current-voltage (I-V) characteristics configuration have been performed using density functional theory (DFT) and non-equilibrium green function (NEGF) method. It has been observed that CNFET can be used for the potential application of gas sensor at room temperature. Out theoretical findings are corroborated with experimental data and this virtual device structure can be converted into physical device to get nano dimensions integrated gas sensoItem Performance Analysis of (13,0) and (17,0) Carbon Nanotube Field Effect Transistors (CNFETs)(Springer, 2020) Gupta, NavneetThis paper explains the comparative analysis of the performance of (13,0) and (17,0) carbon nanotube field-effect transistors (CNFETs). The comparison is done by studying the output and transfer characteristics of CNFETs. Modeling of the total capacitance of cylindrical CNFETs for the two types of chirality (13,0) and (17,0) has also been reported in the paper. It has been observed that (13,0) carbon nanotube has lesser propagation delay, however, but the drain current is higher for (17,0) for the given parameters. This shows that the switching application is better in case of (13,0) for the given parameters.Item Carbon Nanotube Field-Effect Transistors (CNFETs): Structure, Fabrication, Modeling, and Performance(Springer, 2021-05) Gupta, NavneetThe problems associated with attempting to scale down traditional metal oxide field-effect transistors (MOSFET) have led researchers to look into CNT-based field-effect transistors (CNFETs), as an alternative. Though the scaling of MOSFET has been the driving force toward the technological advancement, but due to continuous scaling, various secondary effects which include short channel effects, high leakage current, excessive process variation, and reliability issues degrade the device performance. On the other hand, CNFETs are not subjected to the scaling problems. The operation principle of the CNFET is similar to traditional MOSFET but the conduction phenomena are different. The traditional MOSFETs are based on the drift and diffusion phenomena in which channel length is very large as compared to mean free path of charge carriers whereas the CNFETs are based on ballistic transport conduction mechanism, in which channel length is very small as compared to mean free path of charge carriers. In CNFET, electrons are injected from source to drain and transported through the nanotubes without scattering. Due to ballistic transport the nanotubes act as a perfect conductor for electrons such that the full quantum information of these electrons (momentum, energy, spin) can be transferred without losses. The channel current in CNFETs depends on gate voltage, number of nanotubes in channel, dielectric material and its thickness, and diameter and chirality of carbon nanotubes. So in this chapter we shall discuss different device structures of CNFET, steps involved in the fabrication of CNFETs, advantages and limitations of various methods involved in the synthesis of CNTs, conduction models, and performance parameters.