Effects of Si interlayer conditions on platinum ohmic contacts for p-type silicon carbide

Abstract

A study of Pt ohmic contacts with Si interlayers on p-type SiC (7.0 × 1018 cm-3) was performed as a function of the Si interlayer thickness, deposition temperature, and dopant incorporation. All contacts were ohmic after annealing at 1100°C for 5 min in vacuum. The use of a Si layer was found to decrease the specific contact resistance (SCR) relative to Pt contacts that did not contain Si, regardless of the deposition conditions used in this study. The SCR values were reduced further by three independent effects: the deposition of the Si layer at 500°C, the incorporation of B in the layer, and the design of the Pt:Si layer thicknesses in a 1:1 atomic ratio. By combining all of these effects, the lowest average SCR values (2.89 × 10-4 Ω cm2) were obtained. After annealing for 5 min at 1100°C, x-ray diffraction of the contacts with the 1:1 Pt:Si ratio showed a single phase of PtSi. Analyses by cross-sectional transmission electron microscopy revealed no reaction of the films with the SiC substrate. The electrical characteristics of these contacts were stable after annealing at 400°C and 600°C for 96 h and 60 h, respectively. These results are in contrast to those observed for pure Pt contacts and for contacts containing a higher Pt:Si ratio.