A new diffusion barrier,. Ta-Ru-N, has been tested on ohmic contacts to p(+)-4H-SiC aged at 350 degrees C in air. Specific contact resistance measurements combined with X-ray diffraction, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to evaluate the barriers. Upon aging, all ohmic contacts exhibited an initial change in resistance but stabilized within 100 h, with many samples surviving for 2000 h (the longest time tested). The Ru: Ta ratio in the barriers must be sufficiently high to obtain a long-lived barrier in air. Specific contact resistances as low as 3 x 10(-5), Omega cm(2) were maintained after 2000 h of aging. (c) 2005 Elsevier B.V All rights reserved.