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

The fabrication of IV-IV alloys has generated considerable interest. The possibility of band-gap engineering has made them attractive for devices such as HBTs, MODFETs and also infrared detectors. Recently, it was shown that small amounts of C added to S/sub 1-x/Ge/sub x/ layer can offer the possibility of strain compensation to zero misfit. A tetragonal distortion associated with either a compressive strain (usually present in strained Si/sub 1-x/Ge/sub x/ layer) or a tensile strain is also provided depending on the Ge:C ratio. In this present work, we have investigated the behavior of the Schottky barrier height (SBH) on these IV-IV alloys as a function of the composition of the alloy for different layer thicknesses (above or below the critical thickness), and as a function of the metal used to realize the Schottky contact.