Fermi Level Position At Metal Si1-X-Ygexcy Interfaces

In this work, we have investigated the Schottky barrier heights on n- and p-type Si1-x-yGexCy alloys with Zr, Ti, W, Ni and Pt as metals (Phi (Bn) and Phi (Bp), respectively). Contacts on Si1-xGex alloys showed various behaviors depending on the metal work function Phi (m). For low-Phi (m) metals (Zr, Ti), Phi (Bn) increases with x, while Phi (Bp)(x) decreases. For higher Phi (m) metals (Pt), Phi (Bn) strongly decreases with x. In the particular case of W (intermediate Phi (m) value), Phi (Bp) follows exactly the decrease of the SiGe band gap with x, while Phi (Bn) remains constant. Nevertheless, whatever the metal, the reduction of the sum Phi (Bn)+Phi (Bp) gives the band-gap variation as a function of x, and the Fermi level is located at the same position for both n and p-type layers. A weaker effect of Phi (m) on the Schottky barrier heights is observed compared to pure Si: the position of the Fermi level tends to remain in the range 0.60-0.65 eV below the conduction band, as soon as Ge is adding in Si. W contacts on Si1-x-yGexCy alloys evidenced the strong effect of C on Phi (Bn) and Phi (Bp). The variations of Phi (Bn)(y) or Phi (Bp)(y) cannot be correlated to the band gap. In addition, the position of the Fermi level at the interface depends on the type of the alloy. Nevertheless, as in the case of the binary alloy SiGe, a weaker dependence on Phi (m) compared to that observed for pure Si is shown. High values of the ideality factor with increasing the C content may evidence the presence of interfacial inhomogeneities, which could be correlated to C short range order. The present results have been compared to existing published results. (C) 2001 American Institute of Physics.