Improvement of high temperature stability of nickel contacts on n-type 6H–SiC

The structural and electrical characterisation of nickel contacts on n-type silicon carbide was performed to improve the ohmic behaviour at high temperatures. The formation of nickel silicide (Ni2Si) was observed after annealing in vacuum of Ni/SiC samples at 600 °C, as well as after rapid thermal annealing (RTA) in N2 at 700 for 60 s. The carbon was almost uniformly distributed inside the Ni2Si layer, as monitored by energy dispersion X-ray analysis (EDX). The specific contact resistance ρc was determined by the transmission line method (TLM) for different values of the substrate carrier concentration ND. Ohmic contacts with ρc=3.9×10−5 Ω cm2 were obtained for substrates with ND=7.4×1018 cm−3 after RTA in N2 at 950 °C. The optimised contacts maintain their electrical stability even after annealing in N2 up to 1000 °C.