Schottky's model for the barrier height of a metal-semiconductor inter
face predicts a value of 1.1 eV for Ga on p-type Si. Previous investig
ations of such Schottky diodes have shown that this barrier height is
actually very small. Our results on hydrogen-passivated Si show an int
ermediate barrier height that depends strongly on the properties of th
e passivated surface. We explain this discrepancy as a case of a mixed
-phase interface, where Ga forms a high Schottky barrier to the passiv
ated Si surface and a low barrier to residual defects of the passivate
d surface.