Influence of interface structure on electrical properties of NiGe/Ge contacts

Abstract

We have investigated the electrical properties of NiGe/n-type Ge contacts with various crystalline structures. We found that the Schottky barrier height (SBH) of the NiGe/Ge contact could be modulated by controlling the crystalline structures of the NiGe layer. An epitaxial NiGe(100)/n-type Ge(110) contact shows an SBH 0.15 eV lower than that of the polycrystalline NiGe/n-type Ge(110) contact, whereas the SBH of the epitaxial NiGe(111)/n-type Ge(001) contact is not so low compared with that of the polycrystalline NiGe/n-type Ge(001) contact with Fermi level pinning, even though an epitaxial NiGe layer with good crystalline quality is formed. This distinctive modulation of SBH could not be explained by considering only the metal-induced gap states model. We consider that this modulation of SBHs is a consequence of the variation in the density of the interface states induced by the extrinsic factors, such as the dangling bonds and/or defects. Our results give us a hint that the modulation of the SBH by controlling the crystalline structures is possible.