Superconductivity in Ge and Si via Ga-ion implantation

We present current progress of a unique study featuring the origin and use of superconductivity in highly Ga-doped group-IV semiconductors. Thin films have been prepared via ion implantation and subsequent short-term annealing. Germanium offers a high solubility for Ga acceptors (up to 1 at.%). Thus, superconductivity below about 0.5 K has been devoted previously solely to doping. However, recent atom-probe tomography reveals Ga nano-accumulations rendering the possibility of superconductivity in a proximity coupled network. In silicon, we have investigated a 10 nm thin amorphous Ga precipitation layer (Tc=7 K) that is close to the superconductor to insulator transition. We present high magnetic field measurements up to 40 Tesla and evaluate the critical-field phase diagram. First proof for phase coherence has been detected via magneto-resistance oscillations in lithographically tailored structures. This opens the door for future device fabrication.