The effect of heat treatment on Au Schottky contacts on β-SiC

Thermally stable gold/beta-silicon carbide (β-SiC) Schottky barriers were successfully fabricated by electron-beam evaporation of gold films on appropriately prepared sample surfaces. It was found that the forward current-voltage characteristics of the as-deposited contacts were exponential over at least six orders of magnitude, the ideality factor n was in the range n = 1.5 ± 0.2, and the barrier height φBwas ≃ 1.2 eV. The forward turn-on voltage was 0.6-1.0 V, and, in the reverse direction, soft breakdown occurred in the range 8-10 V. These contacts remained almost unaltered by a 1-h heat treatment at 300°C in argon, and were still rectifying after further heat treatments, first at 500°C for 30 min, and then for one more hour, again at 500°C, but after a final 30-min, 700°C heat treatment, the contacts degraded and showed ohmic behavior. Auger spectroscopy was applied to study the Au-β-SiC interface, both as-grown and after annealing. A gradual outdiffusion of Si was observed, which became more prominent at higher annealing temperatures. However, the SiC interface was found to be an effective barrier to Au diffusion into the semiconductor.