Scientists at NASA’s Glenn Research Center have developed and patented improved ohmic contacts, and a fabrication method for them, that will speed the production of silicon carbide (SiC) sensors and electronics that operate in high-temperature, harsh environments.
Conventional fabrication techniques require multiple time-consuming and costly processes to form ohmic contacts separately onto donor (n-type) and acceptor (p-type) surfaces. Glenn’s innovation creates universal and simultaneous ohmic contacts for both n- and p-type SiC semiconductors without compromising reliability and contact robustness. These ohmic contacts make it significantly less expensive and easier to fabricate high-temperature SiC sensors and electronics that can monitor in real time, even within harsh environments such as jet and rocket engines.
To avoid catastrophic failure, traditional electrical ohmic contacts must be placed at some distance from the optimal position (especially for sensors) in high-temperature environments. In addition, conventional metallization techniques incur significant production costs because they require multiple process steps of successive depositions, photolithography, and etchings to deposit the desired ohmic contact material. Glenn’s novel production method both produces ohmic contacts that can withstand higher temperatures than ever before (up to 600 °C) and permits universal and simultaneous ohmic contacts on n- and p-type surfaces. This makes fabrication much less time-consuming and expensive while also increasing yield.
This innovative approach uses a single alloy conductor to form simultaneous ohmic contacts to n- and p-type 4H-SiC semiconductor. The single alloy conductor also forms an effective diffusion barrier against gold and oxygen at temperatures as high as 800 °C. Glenn’s method enables a faster and less costly means of producing SiC-based sensors and other devices that provide quicker response times and more accurate readings for numerous applications, from jet engines to down-hole drilling, and from automotive engines to space exploration.