Effects of annealing temperature on the structure and electrical properties of tungsten contacts to n-type silicon carbide

Tungsten contacts deposited on n-type 4H-SiC substrates were annealed at temperatures from 700 to 1400 °C and the phase composition of the contact layers was analyzed by TOF-SIMS technique, X-ray diffraction method and scanning electron microscopy. W5Si3 and WC were characterized as the main crystalline phases formed in the contact layer after annealing at 1400 °C and crystallite size was calculated as equal to 74 nm and 73 nm, respectively. Measurements of current–voltage characteristics showed that ohmic character of the contact was obtained after annealing at the highest applied temperature 1400 °C while I–V characteristics of 1200 °C annealed contact showed limited deviation from linearity. The specific contact resistivities equal to 2.42 × 10−5 Ω cm2 and 2.27 × 10−5 Ω cm2 were achieved for 1200 and 1400 °C annealed contacts, respectively. The mechanism of ohmic contact formation was proposed.