Termination-dependence of Fermi level pinning at rare-earth arsenide/GaAs interfaces

Abstract

The properties of metal/semiconductor interfaces are generally described by the metal-induced gap states (MIGS) model. However, rare-earth (RE) arsenide interfaces are found not to follow the MIGS model in having very different Schottky barrier heights (SBHs) for the Ga- or As-terminations of polar (100) or (111) RE-As/GaAs interfaces. Density function supercell calculations find this effect is due to localized defect interface states located on the mis-coordinated atoms of these interfaces that pin their SBHs at very different energies for each termination as determined by the anion sublattice bonding. Band offsets of semiconducting ScN/GaN interfaces also depend on their termination as determined by the same defect interface states. This pinning mechanism dominates any MIGS mechanism when it arises. Nonpolar (110) interfaces have little change in bonding, so they have no defect interface states, and we find their SBH is pinned by MIGS at the charge neutrality level. Hence, traditional MIGS models should be extended to include such interface states in a more general description.