Effect of atomically controlled interfaces on Fermi-level pinning at metal/Ge interfaces

We study electrical properties of metal/Ge contacts with an atomically controlled interface, and compare them with those with a disordered one, where atomically controlled interfaces can be demonstrated by using Fe₃ Si/Ge (111) contacts. We find that the Schottky barrier height of Fe₃ Si/n-Ge (111) contacts is unexpectedly lower than those induced by the strong Fermi-level pinning at other metal/n-Ge contacts. For Fe₃ Si/p-Ge (111) contacts, we identify clear rectifying behavior in I-V characteristics at low temperatures, which is also different from I-V features due to the strong Fermi-level pinning at other metal/p-Ge contacts. These results indicate that there is an extrinsic contribution such as dangling bonds to the Fermi-level pinning effect at the directly connected metal/Ge contacts.