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

Abstract

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°C for 2 min. Specific contact resistances ranged from approximately 5 × 10 −6 to 3 × 10 −5 Ω cm 2 on material with a doping of 1.3 × 10 19 cm −3. The initial AlTi thickness before annealing was found to be critical to controlling the Al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°C for 1 min. These contacts were ohmic with a specific contact resistance between 2 × 10 −5 and 4 × 10 −5 Ω 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.