Investigation of Transport Characteristics of Gallium Oxide FETs and Carbon Nanotube Network based FETs for Emerging Applications
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Kumar, Nitish
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Abstract
Field effect transistors (FETs) are the building blocks of both analog and digital circuits. Silicon is the most widely used semiconductor, but introduction of novel semi-conducting materials with their unique material properties has opened the avenues for significant improvement in many electronic systems. For example, gallium oxide, with its ultra-wide bandgap, can help achieve higher breakdown voltages and switching efficiency, which make it a promising candidate for next generation of RF and power electronics. Similarly, the carbon nanotubes (CNTs) with their superior electrical, thermal, and mechanical properties can help build low-power, transparent, flexible, and wearable electronics. This work aims to study the transport characteristics of gallium oxide FETs and CNT network-based FETs to explore the unique challenges and/or opportunities for future applications.
First, the transport characteristics of a random CNT network-based FET has been investigated using a drift-diffusion model. The unique property of randomness of the networks has been used to develop physically unclonable functions (PUFs). PUFs can enable a hardware based cryptographic technique to prevent unauthorized access of electronics devices. CNT-FETs based PUFs offer new security primitives that can be compatible with the various substrates of the next generation of flexible electronic devices. A new multi-gated CNT-FET design has been proposed, which can further enhance randomness and security of the PUF.
In addition, this work has investigated the electro-thermal transport in β-Ga2O3 based FETs using a combination of modeling and metrology techniques. Low thermal conductivity of β-Ga2O3 leads to self-heating in its FETs and heat dissipation poses a significant challenge for viability of these devices. Accurate prediction of the electrical and thermal characteristics of these devices is needed for efficient thermal management and device design. A thermodynamic carrier transport device model and 3-D diffusive transport model have been developed to investigate the transport characteristics of these FETs. Ultrafast thermal imaging of the FETs has been performed using a thermoreflectance system to understand the temperature rise at short time scales at different operating voltages. The device level passive thermal management techniques has also been investigated. Boltzmann Transport Equation (BTE) based model has been used to understand the effect of ballistic-diffusive transport and complex phonon-phonon energy exchange mechanisms on thermal transport characteristics of β-Ga2O3 thin films and FETs.
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2021-05-04
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Dissertation