Germanium Wafers Possessing Facet-Dependent Electrical Conductivity Properties.

Electrical conductivity properties of Ge {100}, {110}, {111}, and {211} facets have been measured by breaking Ge (100) and (111) wafers to expose {110} and {211} surfaces and contacting the different facets with tungsten probes. Ge {111} and {211} faces are far more conductive than the already conductive Ge {100} and {110} faces, matching with recent density functional theory (DFT) predictions. Asymmetric I-V curves resembling those of p-n junctions have been collected for the {110}/{111} and {110}/{211} facet combinations. The current-rectifying effects stem from different degrees of surface band bending for the highly and less conductive faces and the direction of current flow. This work demonstrates that germanium wafers also possess facet-dependent electrical conductivity responses that can be utilized in the fabrication of novel fin field-effect transistors (finFET).