FLUX-FLOW TRANSISTORS BASED ON LONG YBA2CU3O7-DELTA BICRYSTAL GRAIN-BOUNDARY JUNCTIONS

Josephson flux-flow transistors were made from long YBa2Cu3O7-delta bicrystal grain boundary junctions. A normal metal loop, separated from the junction by an SiO layer, was used as the current control line. The line modulated the critical current, I(c), which for temperatures less-than-or-equal-to 60 K showed the typical dependence for a long junction, while at higher temperatures the regular small junction modulation was seen. Current gain larger than unity was obtained below 70 K. The current gain increased with the junction length, and varied roughly like square-root I(c) when decreasing the temperature. A transresistance larger than 5 OMEGA was obtained at 15 K. Better performance is expected from junctions with higher current densities.