Structural and electrical properties of Ni/Ti Schottky contacts on silicon carbide upon thermal annealing

The evolution of the structural and electrical properties of Ni/Ti/SiC Schottky contacts upon thermal treatments was investigated. The samples were prepared by sequentially evaporating titanium and nickel layers onto silicon carbide (6H-SiC) substrates and were annealed in vacuum in the temperature range 400-650 degreesC. Above 450 degreesC a solid state reaction sets in, giving rise to the formation of nickel silicides (i.e., Ni31Si12 and Ni2Si). During reaction, by increasing annealing temperatures, the electrical characteristics of the contacts showed an increase of the Schottky barrier, along with a decrease of the device leakage current. An inversion of this trend was observed at around 600 degreesC, which can be attributed to the inhomogeneity of the nickel silicide/SiC barrier. The scenario of the reaction of the Ni/Ti/SiC system is presented. The physical information obtained from the study of this bilayer can be extremely important in the control of the electrical properties of Schottky barriers for advanced devices on SiC.