Observation of contact resistivity independence from Schottky barrier height on heavily doped p-type SiGe

The electrical characteristics of Ti/p-SiGe contacts with Ti thicknesses of 3nm and 5nm have been investigated in this paper. TiN was used as a cap layer on Ti. It is observed that as Ti film becomes thinner, Ti/p-SiGe contact resistivity (ρc) increases, but its Schottky barrier height (SBH) decreases, which does not coincide with the regular ρc-SBH dependence. Using TiN/p-SiGe as a control sample, it is concluded that when Ti film is thinned down to nm scale, the contact property is strongly influenced by TiN cap layer.