Contact between High-Tc Superconductor and Semiconducting Niobium-Doped SrTiO₃

The contact between a high- T c superconductor of Er-Ba-Cu-O and a semiconductor of niobium-doped SrTiO 3 has been examined by current-voltage measurements. The rectifying characteristic has been observed at 277 K for a sample with niobium-0.05wt%-doped SrTiO 3 . The breakdown voltage decreases with decreasing temperature or increasing niobium impurity concentration, and the temperature dependence of the breakdown voltage becomes more gradual with increasing niobium impurity concentration.