Control of Schottky barrier heights by inserting thin dielectric layers

The insertion of ultra-thin dielectric layers to lower n-type Schottky barrier heights is shown to partly involve the creation of a net interfacial dipole as well as unpinning of the Fermi level by suppression of metal-induced gap states. The existence of a net dipole requires a lack of cancellation of dipoles at the two interfaces. This requires a different metal(Ge)-O bond density at the two interfaces, in general requiring differing oxygen chemical potentials. This would need the inserted dielectric to be a diffusion barrier, not just able to create dipoles, favoring the use of Al2O3-based or nitrided dielectrics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764521]