Thermally stable ohmic contacts to 6H- and 4H- p-type SiC

Conventional Al ohmic contact to p-type SiC demonstrates poor thermal stability owing to the oxidation of Al at elevated temperatures. In order to solve this problem, new Al based ohmic contacts of Al/Ni/W, Al/Ni/Mo, and A//Ni/Au to p-type SIC were successfully developed. All these contacts become ohmic after annealing at 850/spl deg/C for 2 to 5 minutes. The contact resistivity of these new contacts ranges from 10/sup -4/ to 10/sup -5/ ohm-cm/sup 2/. These new ohmic contacts show excellent thermal stability. The contact resistivity and I-V characteristics remain unchanged after aging at 600/spl deg/C for 300 hours. Chemical depth profiles, obtained by Auger electron spectroscopy, indicate that the refractory cap layer, W, Mo, or Au effectively prevents Al from diffusing to the contact surface and forming Al/sub 2/O/sub 3/.