Conclusions

The barrier heights of Schottky contacts and the band offsets in heterostructures are determined by a continuum of interface-induced gap states (IFIGS). These gap states are linked to the complex band structure of the semiconductors. They are described by two bulk parameters. One is the branch point at which the charge character of the gap states changes from acceptor- to donor-like. The second describes the interface dipole. Physically, it is given by the density of states and the decay length of the interface-induced gap states at their branch point. From a chemical point of view, the concept of the partial ionic character of covalent bonds can be transferred to the bonds at the interfaces. A “bridge” between both approaches is the linear correlation between the adatom-induced core-level shifts on semiconductor surfaces and the differences between the electronegativities of substrate- and adatoms. In summary, the barrier heights of Schottky contacts and the band offsets of heterostructures are consistently and quantitatively explained by the IFIGS-and-electronegativity concept.