Fermi Level Position at Metal-Semiconductor Interfaces

The position of the Fermi level at a metal-semiconductor interface relative to the conduction band has been found to be a constant fraction of the semiconductor band gap for all but 3 of the 14 group IV or III-V semiconductors studied. In all cases, the position was essentially independent of the metal work function. This general result is not inconsistent with the limited theories of surface state energies now available. The three exceptional cases can be understood in terms of a first-order perturbation to the surface state energies correlated with a similar perturbation observed in the energy gap at the (111) zone edge. Experiments are also reported on Ga(As-P) alloys, and two II-VI materials showing distinctly different behavior.