According to a recently funded national partnership directed by Penn State University (PSU), electronics comprising wide bandgap semiconductors offer improved resistance against radiation damage compared to traditional silicon-based electronics.
Researchers received $7.5 million to investigate how to improve radiation resistance in electronics made with gallium nitride, shown here as a transistor wafer undergoing testing on a probe station. Image Credit: Kelby Hochreither/Penn State.
To better estimate and alleviate radiation-triggered damage of wide bandgap semiconductors, the U.S. Department of Defense bestowed the team with a 5-year, $7.5 million Defense Multidisciplinary University Research Initiative Award.
Most of today’s electronics are based on silicon. Wide bandgap semiconductors, such as gallium nitride, have shown advantages over silicon in radio frequency and power electronics. They are also inherently more resistant to radiation due to stronger atomic bonds.
Rongming Chu, Project Lead and Thomas and Sheila Roell Early Career Associate Professor of Electrical Engineering, Penn State University
This radiation resistance, referred to as radiation hardness, guards against deformation caused by radiation from particles and high-energy rays. This feature, Chu said, transforms wide bandgap semiconductors into favorable options for creating electronics used in surroundings with substantial radiation, like in outer space.
However, scientists have not yet reached the total 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. 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.
Rongming Chu, Project Lead and Thomas and Sheila Roell Early Career Associate Professor of Electrical Engineering, Penn State University
Flaws in the structures and materials of electronics can range from negligible to terrible, causing device degradation and failure. Examples of flaws include undesirable impurities, dangling atomic bonds at the interface between different materials, and displacement of atoms from their original locations.
There is a risk of these defects becoming electrically active under a high electric field, with energetic electrons, causing detrimental effects to device performance. Today’s wide bandgap semiconductor electronic devices are designed such that this risk is minimized under normal operating conditions.
Rongming Chu, Project Lead and Thomas and Sheila Roell Early Career Associate Professor of Electrical Engineering, Penn State University
“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,” Chu added.
To better comprehend how radiation results in flaw generation and evolution, how these flaws impact device operation, and how to re-engineer future wide bandgap devices for the ideal radiation hardness, Chu said an interdisciplinary team is essential.
Collaborators include Miaomiao Jin, assistant professor of nuclear engineering; Patrick M. Lenahan, distinguished professor of engineering science and mechanics; and Blair R. Tuttle, associate professor of physics, all from Penn State University; and Tania Roy, University of Central Florida; B. Reeja Jayan, Carnegie Mellon University, and Michael E. Flatté, University of Iowa.
Chu stated that, at PSU, the researchers will make use of the tools and professionals 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.
Rongming Chu, Project Lead and Thomas and Sheila Roell Early Career Associate Professor of Electrical Engineering, Penn State University
“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 multidisciplinary team effort,” Chu added.
The grant will aid 16 graduate students, including 11 at PSU, to carry out multidisciplinary studies covering physics, materials science and engineering, computation, and electrical engineering as they undertake a range of doctorates and master’s degrees.
“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 bridge fundamental research to real-world applications,” Chu said.