The use of unconventional devices, along with exploitation of unique properties of the III-N material system, has the potential to significantly impact both high frequency and high-power systems. In this talk, several device technologies being explored at the University of Notre Dame will be described. Recent demonstrations of scaled GaN-based HEMTs having experimentally-demonstrated ft's of over 370 GHz, indicate that GaN-based devices are attractive not just for microwave power amplification, but also for mm-wave and mixed-signal circuit applications as well. The aggressive device scaling that enables these high speeds also led to the observation of room-temperature plasma wave propagation in GaN-channel HEMTs, suggesting additional avenues for high-frequency device design as well as phenomena to be leveraged for enhanced functionality. In addition, the large polar optical phonon energy in GaN results in transport properties that are distinctly different from most other III-V materials; this can be exploited to engineer devices for improved performance. The details of impact ionization in GaN—important for both power devices and devices such as IMPATT diodes—have also recently been explored and will be presented. Novel processing schemes for heterogeneous integration, high-field edge termination, and thermal management of III-N devices—critical to the exploiation of GaN for high power applications—will also be presented.
Patrick Fay is a Professor in the Dept. of Electrical Engineering at the University of Notre Dame. He received a Ph.D. in electrical engineering from the University of Illinois at Urbana-Champaign in 1996. His research interests include the design, fabrication, and characterization of microwave and millimeter-wave electronic devices and circuits, as well as high-speed optoelectronic devices and integrated circuits. His research also includes the use of micromachining techniques for the fabrication of RF through sub-millimeter-wave packaging. His most recent work focuses on the use of polarization-engineered III-N heterostructures for non-traditional applications including ultra-low-power devices for logic, novel devices for RF/mm-wave switching and routing for advanced communication systems, as well as the exploitation of device nonlinearities for detection and signal processing applications. He established the High Speed Circuits and Devices Laboratory at Notre Dame, which includes device and circuit characterization capabilities at frequencies up to 1 THz. He also oversaw the design, construction, and commissioning of the 9000 sq. ft. class 100 cleanroom housed in Stinson-Remick Hall at Notre Dame, and has served as the director of this facility since 2003. Prof. Fay is a fellow of the IEEE, is an IEEE Electron Devices Society Distinguished Lecturer, and has published 9 book chapters and more than 300 articles in scientific journals and conference proceedings.