Three terminal YBaCuO Josephson device with quasi-particle injection gate

A novel type of three-terminal Josephson device called the SCST (superconducting current switching transistor), was fabricated using high-T_c LnBaCuO (Ln=Y, Er) thin epitaxial and/or polycrystalline films. The hot quasi-particle injection effect on the Josephson (or superconducting) current in the films was closely examined. The zero bias drain current was efficiently suppressed by the injection of the hot quasi-particles through the gate electrode. A comparison of the experimental results and analyses based on the BCS theory suggests that the main mechanism of the current modulation is the nonequilibrium superconductivity due to the accumulation of the excess quasi-particles. The maximum current modulation gain was 5~7 and the modulation current ranged as low as 3~10 A/cm²