High current gain HTS Josephson vortex flow transistors

We have fabricated discrete Josephson vortex flow transistors from yttrium barium copper oxide thin-films on 24 degree strontium titanate bicrystals. The devices have an asymmetric design with the control current fed through an independent control line. We have measured high current gains, in excess of 20 at 77K for a range of several devices, and substantially higher at l ower temperatures. The performance at 77K has been studied and compared wit h theoretical simulations, which have included the effects of noise.