Mechanism of ohmic behavior of Al/Ti contacts to p-type 4H-SiC after annealing

We report on experiments to determine the mechanism of ohmic behavior of Al/Ti contacts to p-type SiC after thermal annealing. After ruling out heavy doping of the SiC surface due to diffusion of aluminum, and electric field enhancement due to surface morphology modification, we propose that the only remaining explanation is alloy formation at the metal-semiconductor interface. We present evidence from x-ray diffraction studies identifying these alloys as Ti3SiC2 and Al4C3, and review corroborating transmission electron microscopy studies. An alloy-assisted ohmic contact mechanism is presented and discussed. (C) 2004 American Institute of Physics.