Systematic investigation of ramp edge junction using Ca-doped and Ga-doped PBCO barrier

摘要

We have investigated systematically the characteristics of ramp edge junctions with Ca- and Ga-doped PBCO barriers. The localized state density g and/or the volume of the state v in the barriers are increased by Ca-doping and decreased by Ga-doping. Ca-doping reduces the I/sub c/R/sub n/ products, and Ga-doping enhances the I/sub c/R/sub n/ products, though the dominant transport mechanisms are direct tunneling for the junctions having I/sub c/R/sub n/ greater than 1 mV. The change in the I/sub c/R/sub n/ products can be interpreted in terms of the proximity effect at the interface states formed by hybridization between the localized states in the barrier and conduction electron states of electrodes. The ideal superconductor-insulator interface at the junction interfaces is required to enhance I/sub c/R/sub n/ products.