| Description |
Power electronic systems form the backbone of the modern world's electrical infrastructure. With the world's global energy consumption on the rise, "energy security" has become the biggest concern of this century. Energy-efficient low-cost power systems can reduce energy waste and accelerate the adoption of low-carbon energy sources toward a sustainable, cleaner, and "greener" future. Solid-state power semiconductor devices are at the heart of these power electronic systems that process electricity for communications, health, defense, and energy sectors. Developing power devices using wide-bandgap (WBG) semiconductors such as SiC and GaN have made high-power switch conversion technology a commercial reality. Thanks to this, we now have products that are smaller, faster, efficient, and more ubiquitous. β-Ga2O3 has emerged as a material that demonstrates numerous strengths for next-generation high voltage/power applications. Its projected material power figure of merit (εsμnEC3) is almost 3500×, 10×, and 4× higher than that of Silicon, SiC, and bulk GaN. In this work, state-of-the-art electron mobilities, contact resistance values, breakdown voltages, and power figures of merit are demonstrated in β-Ga2O3 epitaxial films and devices. High-purity and high crystal quality metalorganic vapor phase epitaxy grown unintentionally doped and Si-doped β-Ga2O3 thin films with electron mobility values close to the predicted theoretical maximum (~ 200 cm2/Vs) are achieved at low (600°C) and high (800°C) growth temperatures through optimized growth conditions. A low-temperature MOVPE masked ohmic contact regrowth technique is developed that demonstrates a record low contact resistance value. Multi-kilovolt (up to 4.5 kV) class β-Ga2O3 transistors are demonstrated with state-of-the-art power figures of merit exceeding several times the theoretical maximum of Silicon. A channel-buffer stack engineering is demonstrated that enabled record-high electron mobility values in doped β-Ga2O3 films. High-current and VBR (over 2 kV) homoepitaxial β-Ga2O3 MOSFETs are realized on an engineered β-Ga2O3/SiC composite substrate - for enhanced bottom-side device cooling. Tri-Gate β-Ga2O3 MESFETs with record high power figure of merit (~0.95GW/cm2) and high-current β-Ga2O3 MOSFETs with MOVPE-grown Al2O3 gate dielectrics are also demonstrated. This dissertation presents some of the critical results in Ga2O3 epitaxy/devices using MOVPE technology and provides the foundational steps towards next-generation energy efficient power electronics. |
