SUMMARY

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 makes 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.
This work has first 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 has been developed to investigate the transport characteristics of these FETs. Ultrafast thermal imaging of the FETs is being performed using a thermoreflectance system to understand the temperature rise at short time scales at different operating voltages. Boltzmann Transport Equation (BTE) based model will be developed to understand the effect of ballistic-diffusive transport on transport characteristics of these FETs.
Next, 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.