03/14/2025
By Danielle Fretwell

The Francis College of Engineering, Department of Electrical and Computer Engineering, invites you to attend a Doctoral Dissertation defense by Alexander Senckowski on: Developing Electronic and Optoelectronic Devices and Sensors with Wide bandgap Semiconductors

Candidate Name: Alexander Senckowski
Degree: Doctoral
Defense Date: Friday, March 28, 2025
Time: 3 - 5 p.m.
Location: ETIC, Room 445

Advisor: Xuejun Lu, Ph.D., Professor, Department of Electrical and Computer Engineering, University of Massachusetts Lowell

Committee Members:
1. Xingwei Wang, Ph.D., Professor, Department of Electrical & Computer Engineering, University of Massachusetts Lowell
2. Corey Shemelya, Ph.D.
3. Evelyn Hu, Ph.D., Tarr-Coyne Professor of Applied Physics and Electrical Engineering, Harvard School of Engineering and Applied Sciences at Harvard University

Brief Abstract:
Due to their superior material properties, wide bandgap and ultrawide bandgap semiconductors are increasingly used for electronic and optoelectronic applications. In this dissertation, electronic and optoelectronic devices and sensors are developed with ultrawide bandgap beta-gallium oxide (Ga2O3) and wideband gap 4H-silicon carbide (4H-SiC) single crystal semiconductors. These devices include a novel lateral normally-off Ga2O3 power transistor, a solar-blind UV photodetector and a 4H-SiC passive wireless antenna temperature sensor.

Power electronics fabricated with Ga2O3 are necessary for increased efficiency and breakdown voltage over devices fabricated with currently used materials. Power electronics control and convert electrical power and have applications in renewable energy, consumer devices, automotive, aerospace, rail and robotics. In this work a novel lateral Ga2O3 power transistor is designed, modeled and simulated with a p-type gate for normally-off operation while achieving an ultra-high breakdown voltage. The simulated 10-kilovolt normally-off lateral design has a power figure of merit greater than that of a vertical device.

Photodetectors fabricated with beta-gallium oxide are naturally solar blind due to the ultrawide bandgap of Ga2O3. This allowed for the development of ultraviolet (UV) Ga2O3 photodetectors with a straightforward fabrication process. The UV photodetectors were tested with UV light of less than 250 nanometers and demonstrated good performance enabling low-cost easily fabricated solar-blind UV photodetectors.

Due to its extreme melting point and chemical inertness, a wireless passive temperature sensor fabricated with 4H-SiC can withstand high temperatures and harsh environments such as boilers, furnaces, turbine engines, steam turbines, space probes and experiments. Industrial boilers consume significant energy and are a major source of greenhouse gas emissions. Remote wireless temperature monitoring of industrial boilers would allow for a reduction in energy consumption, greenhouse gas emissions and lower costs. A 4H-SiC wireless passive antenna temperature sensor is developed and demonstrated that operates on the wireless mutual coupling of two antennas. The relatively simple antenna temperature sensor can withstand temperatures exceeding 1000 °C. An equivalent circuit model is developed for the mutual coupling between antennas that agrees well with the experimental data in the weak antenna coupling regime.