FERMI-LEVEL PINNING IN SCHOTTKY DIODES ON IV-IV-SEMICONDUCTORS - EFFECT OF GE-INCORPORATION AND C-INCORPORATION

We have investigated the phenomenon of Fermi level (E-F) pinning at th e interface between tungsten and SiGeC alloys with 0 less than or equa l to x less than or equal to 33% and 0 less than or equal to y less th an or equal to 1.25%. In an attempt to throw lights on the mechanisms responsible for the Fermi level pinning, we have measured Schottky bar rier dependence on composition, strain retained in the semiconductor a nd temperature. For pure Si, the Fermi level is pinned relative to the valence band-Phi(Bn) follows the bandgap variations with the temperat ure. On the other hand, the addition of Ge results in a Fermi level pi nning relative to the conduction band-Phi(Bn) remains constant whateve r the composition, the strain in the films and the temperature. The ro le of C is still puzzling. The addition of C does not modify the barri er in n-SiGe films but leads to a large decrease of the barrier height on n-SiC.