Niobium Josephson junctions with doped amorphous silicon barriers

Nb-(a-Si)-Nb Josephson devices have been prepared by rf sputtering. The silicon films were deposited in an argon-hydrogen atmosphere. Such films can be activated as either n- or p-type semiconductors by the incorporation of phosphorus or boron, and the Fermi level of the material can be moved a considerable fraction of the bandgap. The Josephson current density of n-type layers is found to be substantially greater than p-type layers of the same thickness.