Tantalum carbide ohmic contacts to n-type silicon carbide

Tantalum carbide contacts with and without Au, Pt, and W/WC overlayers on n-type 6H-SiC (0001) were ohmic after annealing at temperatures between 800 and 1075 degrees C. Specific contact resistivities (SCRs) were calculated from current-voltage measurements of transmission line model patterns at temperatures ranging from 20 to 400 degrees C in air. The minimum SCRs at room temperature on SiC (2.3x10(19) cm(-3)) for TaC and for TaC with Pt and Au overlayers were 2.1x10(-5), 7.4x10(-6), and 1.4x10(-6) Omega cm(2), respectively. The SCRs for both the Au/TaC/SiC (5.3x10(-7)Omega cm(2)) and the Pt/TaC/SiC (7.5x10(-7) Omega cm(2)) samples decreased with measurement temperature to 200 and 400 degrees C, respectively, while the latter samples showed reversibility after heating to 400 degrees C. W/WC/TaC/SiC samples showed the best stability after annealing at 400 degrees C for 144 h in vacuum. Changes in the electrical characteristics were correlated with increases in O incorporation in the contacts as a result of annealing. Investigation of the TaC/SiC interface by transmission electron microscopy indicated that there was little or no reaction between the materials. (C) 1999 American Institute of Physics. [S0003-6951(99)00551-3].