ANALYTICAL MODELLING AND NUMERICAL SIMULATION OF PLASMA-ASSISTED GATE ALL AROUND CARBON NANOTUBE FIELD EFFECT TRANSISTOR

Abstract

Carbon Nanotube Field-Effect Transistors (CNTFETs) are becoming the torch-bearers of advancements in the realm of electronics. The semiconductor industry's backbone, traditional silicon-based transistors, is reaching its scaling limits. Power consumption, heat dissipation, and quantum effects become increasingly pressing as the size of these transistors continues to decrease. CNTFETs may be able to help us get around these restrictions by leveraging the use of the distinct properties of Carbon Nanotubes (CNTs). CNTFETs are desirable for use in cutting-edge electronics because of their excellent electrical characteristics. Due to their great carrier mobility, CNTFETs may provide rapid processing and enhanced efficiency. In response to the growing need for low power electronic devices, their high current-carrying capacity makes it possible for these devices to function efficiently. In addition, CNTFETs have potential applications in bioelectronics and sensing. Their great sensitivity and biocompatibility make them useful in biosensors, implantable devices, and bioelectronic interfaces. Precision detection and monitoring of biological species are leading to new possibilities in healthcare, diagnostics, and personalised medicine. In conclusion, the quest for high-performance, energy-efficient, flexible, and bio-compatible electronic devices has led to the development of CNTFETs as a solution to the limits possessed by conventional silicon-based transistors. The thesis aims to shed light on the potential of Plasma-Assisted Gate-All-Around CNTFET technology to revolutionise the future of electronic devices by examining its development and many applications. The research demonstrates the effect of plasma parameters on the performance of a simulated device known as Plasma-Assisted Vertically Aligned Dual-Metal Carbon Nanotube Field-Effect Transistor (VA DMCNFET). A vertically aligned semiconducting Carbon Nanotube (CNT), produced via the Plasma-Enhanced Chemical Vapour Deposition (PECVD) technology, has been used as the channel. A typical Si-based Nanowire Field-Effect Transistor (NWFET) may be compared to the proposed device, which demonstrates a vi MANSHA KANSAL, Delhi Technological University considerable increase in performance. The DC and analogue performance of the VA DMCNFET is analysed for various plasma parameters corresponding to different values of CNT channel radius (for fixed CNT channel length) and varied values of CNT channel length (for fixed CNT channel radius). It has been found that lower values of plasma parameters are necessary for higher values of drain current, transconductance, output conductance, and cutoff frequency, as well as lower values of threshold voltage and channel resistance. On the other hand, higher values of plasma parameters are necessary for a better ION/IOFF current ratio, early voltage, and gain of the proposed device. It is possible to increase the device's efficiency and, as a result, its applicability and performance in real-world settings by making alterations to the plasma parameters. Further in this study, the simulation analysis of a novel device known as a Plasma Assisted Dual-Material Stacked Gate-Oxide Carbon Nanotube Field Effect Transistor (DM-SGCNFET) is shown. This device has a stacked gate oxide structure that is composed of two oxides: SiO2 and HfO2. The performance metrics of the simulated device are compared with a SiO2-based DM-CNFET for changing sets of plasma characteristics that correlate to different values of channel length. Comparing the DM SGCNFET to the DM-CNFET, the in-depth study reveals that the former has superior characteristics in terms of the drain current, transconductance, output conductance, early voltage, gain, gate capacitance, improved switching ratio and lower channel resistance. The novel architecture of DM-SGCNFET paves the way for the device to be a suitable candidate for digital and analogue applications that need high efficiency. This work investigates the simulated device further for its linearity distortion performance. This is done by analysing the values of gm2, gm3, VIP2, VIP3, IIP3, IMD3, and the 1-dB compression point for varying plasma parameter values. The results show promising application potential for the simulated device in wireless communication systems. In addition, this study develops a HfO2 based Plasma-Assisted Gate All Around Carbon Nanotube Field Effect Transistor (GAA-CNTFET). The results of the study conclude that utilising HfO2 results in improvements in all the observed performance metrics, including higher values for drain current, transconductance, output conductance, early voltage, and gate capacitance. The simulated device was put to MANSHA KANSAL, Delhi Technological University vii study for sensing applications. This is achieved by implementing a cavity in the oxide layer and using the notion of dielectric modulation, which makes it possible to discover the change in performance characteristics of the device upon altering the dielectric permittivity of the molecule inside the cavity. The higher the dielectric constant value, the better the performance and the more sensitive the device will be. The findings of this research provide useful information for quantifying the device's potential uses in the sensing fields of biology, the environment, and other important sectors. Thermal stability and conductivity shown by CNT is another fascinating area of research as it opens the doors for unprecedented applications. The study showcases the robustness and stability shown by a simulated DM-SGCNFET device by testing it at different temperature values for temperatures up to 500K. Precision-demanding industries such as aerospace, military, and heavy-scale industries can take benefit from the findings of this study to develop new-age solutions