What is the role of the metal on the Fermi-level position at the interface with IV-IV compounds?

The Schottky barrier height of Ti and W on n-type and p-type Si(1-x-y)Ge(x)C(y) alloys has been investigated as a function of the composition and for different states of strain of the epilayers. The barrier on p-type, Phi(Bp), differs slightly on the metal. However, the variation of the band gap is better correlated to the barrier heights to W than those to Ti. In the case of n-type, the addition of Ge in Si does not modify the position of the Fermi level at the interface with W, while it strongly shifts E(F) towards the valence band at the interface with Ti. In addition, we have observed a degradation of the interfaces for the high Ge content, and this degradation is more pronounced for Ti. In conclusion, the dependence of the Schottky barrier height on the metal workfunction is more reduced for IV-IV compounds than for pure Si and the addition of Ge leads to a change in the Fermi level pinning position with Ti.