Methods for forming germanium and silicon germanium nanowire devices

A method for forming nanowire semiconductor devices includes a) providing a substrate including an oxide layer defining vias; and b) depositing nanowires in the vias. The nanowires are made of a material selected from a group consisting of germanium or silicon germanium. The method further includes c) selectively etching back the oxide layer relative to the nanowires to expose upper portions of the nanowires; and d) doping the exposed upper portions of the nanowires using a dopant species.