Understanding the impact of radiation on silicon carbide devices for space applications

The first results of the ETH Zurich and ANSTO collaboration focused on silicon carbide (SiC) devices have been reported in two publications.

Dr. Corinna Martinella, formerly a senior scientist at ETH Zurich, said in a LinkedIn post that the research advances an understanding of the basic mechanisms of radiation damage in SiC power devices exposed to heavy ions.

An article in IEEE Transactions on Nuclear Science describes the testing of how commercial silicon carbide (SiC) power devices, including MOSFETs and Junction Barrier Schottky (JBS) diodes, respond to space-like radiation at a microscopic level.

By using a highly focused beam of particles at the Center for Accelerator Science, that either travel deep or stay near the surface, they studied how different kinds of radiation affect the devices.

They found that short-range particles could cause a type of damage called single event leakage current (SELC) in both older and newer versions of these devices.

Monte Carlo simulations performed at ANSTO helped explain how particle depth affects the damage. In particular, when particles strike certain areas of a diode, they increase the electric field and trigger a chain reaction of ionization, which may lead to lasting defects.

Some parts of the devices, such as the source and the gate metal lines showed no signs of damage. However, there were differences in how the devices reacted depending on whether the particle beam hit directly on the source pad or off to the side. A protective polyimide layer reduced how deeply ions could penetrate in off-pad areas.

Dr. Martinella extended thanks to Dr. Ryan Drury and Dr. Zeljko Pastuovic for their invaluable support during the experiments, and to Dr. Stefania Peracchi for leading the preparation of the test campaign at ANSTO and for significant contributions throughout the entire project. All are co-authors on the publication.

A second paper also in IEEE Transactions on Nuclear Science investigated the relation between SEEs caused by heavy-ion irradiation and defects in SiC devices. First author Ph.D. student Helton De Medeiros used heavy-ion irradiation with different linear energy transfers and ion penetration ranges to investigate the radiation tolerance of SiC power diodes.

Single event leakage current degradation was observed for ion ranges shorter than the top crystalline layer. Other techniques were applied to explain the root cause of the observed radiation effects.