Thermally stable low resistivity ohmic contacts for high power and high temperature SiC device applications

Ti/Al/p-SiC and Ni/n-SiC ohmic contacts with improved electrical and thermal properties in respect to their application in high power and high temperature SiC devices are reported in this work. Contact resistivity as a function of annealing was investigated over the temperature range of 700°C -950°C. The lowest resistivity of 1.42×10^-5 Ω.cm² for the Ti/Al contact was obtained after annealing at 900°C while for the Ni contact the lowest resistivity of 4.9×10^-6 Ω cm² was achieved at 950°C. The contact stability during prolonged ageing and at high operating temperatures and current density was studied as a criterion for their reliability. It was found that both contacts were thermally stable during ageing in an inert ambient (N₂) at high temperature of 600°C for 100 hours as well as at operating temperatures up to 450°C in air and at current density of 10³ A/cm² passed through the contacts during the heating. The improved electrical and thermal properties of the Ti/Al/p-SiC and Ni/n-SiC ohmic contacts were demonstrated in the power p-n SiC diode developed.