Researchers have solved a longstanding physics puzzle, explaining why electronic devices can fail catastrophically when exposed to radiation. Their findings may hold the key to engineering new electronics that can better withstand extreme environments, with applications ranging from nuclear energy to space exploration.
The discovery stems from work the researchers were doing on aluminum nitride (AlN), which is an ultrawide bandgap semiconductor. That means AlN can be used in electronic devices that handle large power loads. In theory, AlN also holds promise for use in extreme environments, such as radioactive settings.
To test that theory, the researchers wanted to explore a phenomenon called single-event burnout (SEB), which is when an electronic device is exposed to radiation and a single energetic particle causes catastrophic failure in the device - making the device inoperable and causing structural damage. SEB occurs when high voltage is applied to a device that is exposed to radiation. Different devices can handle different amounts of voltage before SEB occurs.
"We wanted to characterize AlN electronics that we pioneered to see how much power the electronics could handle before SEB took place," says Cristyan Quiñones, corresponding author of a paper on the work and a recent Ph.D. graduate from North Carolina State University.
"The design of a device affects how much voltage a semiconductor material can sustain before SEB occurs. So, if you want to compare the performance of one material to another, you have to look at electric field rather than voltage. And when we compared the electric field AlN could sustain to other semiconductors, we found that AlN could handle significantly higher fields."
To better understand what they were seeing, the researchers analyzed the data from their experiments in conjunction with the available data on SEB in other materials. Ultimately, the researchers used computational simulations to develop an analytical model that explains the actual physics behind SEB.
"Before, we knew SEB happened, and we could test a device's capacity to withstand SEB," says Quiñones. "But now we know why."
When a device is exposed to radiation, heavy ions pass through the material. These ions generate charge carriers in the material and, as voltage is applied to the device, the positive and negative charges separate. This creates a localized electric field. And when that electric field reaches a critical magnitude, it triggers an avalanche of electrons - which leads to a lot of energy being released in a very small area. In other words: kaboom. That is the SEB.
"Understanding the actual physics behind SEB is important," says Ramón Collazo, co-author of the paper and a professor of materials science and engineering at NC State. "Because understanding allows for the possibility of engineering materials for use in radiation-resistant devices, as well as designing more resistant devices themselves.
"We could not do that before, because we did not know what was actually happening in detail," says Collazo. "This new understanding means we can develop design rules to harden devices against radiation and minimize the damage caused by SEB."
The researchers tested their analytical model to see whether it was capable of explaining the observed SEB data from other devices and materials and found that it fit the data.
"Our model was able to explain what we were seeing across the board," says Quiñones. "It was exciting."
"We think this model will be a valuable tool for developing devices with applications ranging from nuclear energy and space exploration to biomedical technologies and fusion experimentation," says Collazo.
The paper, "Single-event burnout of AlN diodes under heavy-ion irradiation," is published in IEEE Transactions in Nuclear Science. The paper was co-authored by Michael Carter, a Ph.D. student at NC State; Zlatko Sitar, the Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State; Jason Osheroff of the NASA Goddard Space Flight Center; and Pramod Reddy, Dolar Khachariya, Seiji Mita and Ronny Kirste of Adroit Materials, Inc.
This work was supported in part by the Air Force Office of Scientific Research under grants FA9550-24-1-0269 and FA9550-19-1-0114; the Army Research Office, under grant W911NF-22-2-0171; the Defense Advanced Research Projects Agency, under grant HR0011-24-9-0457; and a NASA Space Technology Graduate Research Opportunity (NSTGRO 80NSSC22K1198).
