The role of nickel and titanium in the formation of ohmic contacts on p-type 4H?SiC

The formation of low resistivity ohmic contacts to p-type 4H?SiC is achieved. Transfer length method (TLM)-based structures were fabricated on 0.8??m thick epitaxial p-type silicon carbide (4H?SiC) layers. TLM metal patterns were obtained by a lift-off procedure and electron beam deposition of Ni, Ti and Al. The electrical properties of the contacts were examined using current/voltage measurements. Contact resistivity as a function of annealing was investigated over the temperature range from 700 to 1000??C. The lowest contact resistivity of 1.5???10?5?? cm2?was obtained for the Ni/Ti/Al/Ni contact after annealing at 800??C for 90?s. Using secondary ion mass spectrometry, energy-dispersive x-ray spectroscopy and x-ray diffraction measurements, we quantitatively and qualitatively determined the formation and the nature of the ohmic contact to p-type SiC.