21 April 2022
Penn State leading five-year, $7.5m study of radiation effects on wide-bandgap semiconductors
Compared with conventional silicon-based electronics, electronics employing wide-bandgap semiconductors promise better resistance against radiation damage. So, to better predict and mitigate radiation-induced damage of wide-bandgap semiconductors, the US Department of Defense has awarded a five-year, $7.5m Defense Multidisciplinary University Research Initiative (MURI) Award to a new national collaboration led by Penn State University.
“Wide-bandgap semiconductors, such as gallium nitride, have shown advantages over silicon in radio frequency and power electronics,” notes Rongming Chu, Thomas and Sheila Roell Early Career Associate Professor of Electrical Engineering, who is spearheading the project. “They are also inherently more resistant to radiation due to stronger atomic bonds.”
This radiation hardness protects against damage caused by radiation from high-energy rays and particles, making wide-bandgap semiconductors promising candidates for building electronics used in environments with significant radiation (such as outer space), notes Chu. However, researchers have yet to reach the full potential of radiation hardness in wide-bandgap semiconductor electronics.
“Preliminary studies have indicated that the radiation resistance appears to be limited by defects in the semiconductors, rather than by the material’s intrinsic properties,” Chu says. “In this project, we seek to understand the radiation effects of these defects so that we may develop a strategy to redesign the wide-bandgap semiconductor device for the ultimate radiation hardness.”
Examples of defects include unwanted impurities, displacement of atoms from their original sites and dangling atomic bonds at the interface between dissimilar materials. “There is a risk of these defects becoming electrically active under a high electric field, with energetic electrons, causing detrimental effects to device performance,” Chu says. “Today’s wide-bandgap semiconductor electronic devices are designed such that this risk is minimized under normal operating conditions. However, radiation can force the device out of its normal operating condition by exciting additional energetic electrons interacting with the pre-existing defects. It can also knock atoms out of their original positions, modifying pre-existing defects and generating new defects.”
To better understand how radiation causes defect generation and evolution, how these defects affect device operation and how to redesign future wide-bandgap devices for the optimum radiation hardness, an interdisciplinary team is critical, believes Chu. Collaborators include Patrick M. Lenahan, distinguished professor of engineering science and mechanics; Miaomiao Jin, assistant professor of nuclear engineering; and Blair R. Tuttle, associate professor of physics (all from Penn State); and Tania Roy, University of Central Florida; B. Reeja Jayan, Carnegie Mellon University, and Michael E. Flatté, University of Iowa. Chu notes that, at Penn State, the team will leverage the tools and experts affiliated with the Radiation Science and Engineering Center and the Nanofabrication and Materials Characterization User Facilities at the Materials Research Institute.
“The strength of our project comes from a combination of expertise: my research group’s capabilities on gallium nitride devices, Dr Lenahan’s expertise in defect spectroscopy, Dr Jin’s radiation damage modeling, Dr Tuttle’s defect theory work, Dr Roy’s electrical characterization of radiation effects, Dr Jayan’s defect structure characterization and Dr Flatté’s transport theory work,” Chu says. “The teamwork also extends beyond the investigators of this MURI project — especially Dr Michael Lanagan, professor of engineering science and mechanics, who was very instrumental in coordinating this multi-disciplinary team effort.”
The grant will support 16 graduate students, including 11 at Penn State, to perform multi-disciplinary research encompassing physics, computation, materials science and engineering, and electrical engineering as they pursue a variety of master’s degrees and doctorates.
“Not only will the research prepare next-generation technologists to take on technical challenges but, through our collaborative work with national laboratories and industry stakeholders, the students will also learn the professional skills needed to bridge fundamental research to real-world applications,” Chu says.