On the band-structure lineup at Schottky contacts and semiconductor heterostructures

The band-structure lineup at semiconductor interfaces is explained by the intrinsic interface-induced gap states (IFIGS) that derive from the complex band structures of the semiconductors. The barrier heights of metal-semiconductor or Schottky contacts as well as the band-edge offsets of semiconductor heterostructures are composed of a zero-charge-transfer term plus an electrostatic-dipole contribution which are determined by the IFIGS branch-point energies of the semiconductors and the electronegativity difference of the two materials in contact, respectively. This concept will be illustrated by experimental core-level shifts induced by metal adatoms on group-IV semiconductor surfaces. Choosing Si and SiO2 Schottky contacts and heterostructures as typical examples, it will be demonstrated that the IFIGS-and-electronegativity concept self-consistently explains the barrier heights of Schottky contacts and the valence-band offsets of heterostructures. The IFIGS-and-electronegativity concept also resolves the alleviation of the Fermi-level pinning by ultra-thin insulator interlayers in Schottky contacts. Finally, the modification of Schottky barriers by atomic interlayers will be discussed.