Titanium and aluminum-titanium ohmic contacts to p-type SiC

Very low resistance ohmic contacts to p-type SiC were fabricated by depositing a 90-10 wt.% alloy of Al and Ti followed by a high temperature anneal of approximately 1000 degrees C for 2 min. Specific contact resistances ranged from approximately 5 x 10(-6) to 3 x 10(-5) Ohm cm(2) on material with a doping of 1.3 x 10(19) cm(-3). The initial Al-Ti thickness before annealing was found to be critical to controlling the AI-TI sheet resistance during the anneal. In addition, chemically etching the Al-Ti layer after annealing revealed pitting indicative of severe reaction between the Al-Ti and SiC surface, as confirmed by Rutherford Backscattering. In contrast, ohmic contacts to the same SiC material were fabricated by depositing pure Ti and annealing at 800 degrees C for 1 min. These contacts were ohmic with a specific contact resistance between 2 x 10(-5) and 4 x 10(-5) Ohm cm(2). Examination of the SiC surface after chemically etching away the annealed contact revealed a smooth surface, suggesting a much more planar Ti/SiC interface. (C) 1997 Elsevier Science Ltd.