Superconductivity in p-doped elemental semiconductors

We report the first observation of superconductivity in heavily p-type doped Germanium at ambient-pressure conditions. Using advanced doping and annealing techniques, we have fabricated a highly Ga-doped Ge (Ge:Ga) layer in near-intrinsic cubic Ge. Depending on the detailed annealing conditions, we demonstrate that superconductivity can be generated and tailored in the p-doped semiconducting Ge host at temperatures as high as 0.5 K. Critical-field measurements reveal the quasi-two-dimensional character of superconductivity in the ~ 60 nm thick Ge:Ga layer. We find critical magnetic in-plane fields up to about 1T, even slightly larger than the Pauli-Clogston limit. There might be interest in the technological potential of on-chip thin-film superconductivity in a semiconducting environment demonstrated here as our preparation method is compatible with state-of-the-art semiconductor processing used nowadays for the mass production of logic circuits. After its finding in Si [1] and diamond [2], our work adds another unexpected observation of superconductivity in doped elemental semiconductors and in one of the few remaining ‘islands of the periodic table of elements’ on which superconductivity has not been found so far.