SUBJECT: Ph.D. Dissertation Defense
BY: Samuel Kim
TIME: Tuesday, August 16, 2022, 9:00 a.m.
PLACE:, Virtual
COMMITTEE: Dr. Samuel Graham, Chair (ME)
Dr. Satish Kumar (ME)
Dr. Suresh K. Sitaraman (ME)
Dr. Sukwon Choi (PSU)
Dr. Andrew J. Green (AFRL)


Ultra-wide bandgap (UWBG) semiconductors like β-type gallium oxide (β-Ga2O3) show promise for the development of next-generation high power density electronics devices such as RF and power electronics. The large bandgap (4.8 eV), high breakdown fields (8 MV/cm), and excellent thermal stability of β-Ga2O3 give promise to the production of low-loss power switching devices with large breakdown voltage, and potentially allows for high-temperature and deep space operation. However, a major drawback of β-Ga2O3 arises from its poor thermal conductivity, which results in devices with unacceptably high junction-to-package thermal resistance. While there is considerable promise for future devices made from UWBG materials, their adoption as a technology will hinge upon novel approaches to address heat dissipation at the die level which will enable high power density operation. The aims of this thesis are i) to develop novel thermal management strategies to reduce the junction-to-package thermal resistance for devices made from low thermal conductivity UWBG materials for both lateral and vertical devices, ii) to conduct an analysis of architectures for homoepitaxial β-Ga2O3 metal-oxide semiconductor field effect transistors (MOSFETs) to optimize the device thermal performance and verify experimentally, and iii) to optimize thermal management design for both steady-state and transient-state of UWBG transistors. Overall, the optimal thermally-aware design for vertical and lateral structures for steady-state and transient applications will be provided by investigating the device layout such as substrate orientation, configuration of electrodes (number of fingers, channel width, location of metallization pads), dielectric heat spreader, and thermal boundary conductance between metal and β-Ga2O3.