Superconducting Tunnelling in Metal-Semiconductor Junctions

Abstract

Superconducting tunnelling effects were observed for mechanically contacted Nb–Si, Pb–Si, and Nb–GaAs junctions. The I–V curves of Nb–Si junctions largely deviate from the usual BCS curve. Deviations for Nb–GaAs and Pb–Si junctions are much smaller than that for a Nb–Si junction. This large deviation is explained by the uniformly distributed surface states on the boundary. The upper critical fields H c2 and H c3 of the junctions are much larger than those of a bulk niobium.