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 °C. Specific contact resistivities (SCRs) were calculated from current–voltage measurements of transmission line model patterns at temperatures ranging from 20 to 400 °C in air. The minimum SCRs at room temperature on SiC (2.3×1019 cm−3) for TaC and for TaC with Pt and Au overlayers were 2.1×10−5, 7.4×10−6, and 1.4×10−6 Ω cm2, respectively. The SCRs for both the Au/TaC/SiC (5.3×10−7Ω cm2) and the Pt/TaC/SiC (7.5×10−7 Ω cm2) samples decreased with measurement temperature to 200 and 400 °C, respectively, while the latter samples showed reversibility after heating to 400 °C. W/WC/TaC/SiC samples showed the best stability after annealing at 400 °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.