Kyoto Researchers Fix Two Long-Standing Flaws in Silicon Carbide Electronics

For more than 20 years, silicon carbide (SiC), a semiconductor material that can withstand extreme heat, has been seen as promising for electronics that must function in harsh environments, but that promise has rarely translated into practical devices. Researchers at Kyoto University say the field has been held back because engineers kept applying silicon-era design thinking to a fundamentally different material, according to first author Mitsuaki Kaneko.

The team focused on junction field-effect transistors (JFETs), a type of transistor that earlier work suggested could be combined into low-power complementary circuits capable of operating under extreme conditions. But the group's previous SiC JFETs, built with conventional top-gate structures on semi-insulating substrates, suffered from two problems: poor control over the transistor's threshold voltage, and substantial current leakage at high temperatures.

Rather than inventing an entirely new manufacturing process, the researchers used industry-standard fabrication methods with two changes: a bottom-gate structure to improve control over threshold voltage, and well-based isolation in place of the semi-insulating substrate to cut high-temperature leakage. The redesigned transistor worked on the team's first attempt and continued operating at 600°C, with the bottom-gate architecture substantially improving threshold voltage control and sharply lowering leakage current to close to the theoretical limit expected from SiC's own properties.

The results show SiC is already a mature power device material, the researchers said, and highlight the new bottom-gate structure's potential for building reliable SiC integrated circuits for extreme temperatures. Significant challenges remain before the technology reaches practical use: the team plans to develop more complex circuits, expand fabrication to wafer-level production, and ensure complete device packages can withstand extreme environments. The work, "Over 600°C operation of ion-implantation-based SiC bottom-gate JFETs" by Kaneko, Shunya Shibata and Tsunenobu Kimoto, was published August 17 in APL Electronic Devices.