DC and AC responses of Josephson vortex flow transistors with high Tc superconducting thin films

We fabricated Josephson vortex flow transistors (JVFTs) with a parallel array of Josephson junctions that were prepared using c-axis-oriented 100-nm-thick YBa2Cu3O7-delta,5 (YBCO) thin films grown on 24 degrees bicrystal MgO (100) substrates. We observed clear modulations of the critical current and the flow voltage with DC current input to the control line that was inductively coupled to the array of junctions. From the results, we estimated the parameters of the device, e.g., the mutual inductance and the self-inductance, and calculated the operation frequency at which the device potentially exhibited these parameters. Moreover, the current gain and the transresistance were evaluated and found to be 0.5 and 0.15 Omega, respectively. In addition, we observed the high-frequency responses of the JVFT to the input AC current of the sine wave or the square pulse wave. A clear oscillation of the output voltage could be observed with a 1 MHz sine wave and 250 kHz square pulse wave. We also discussed the feasibility of higher frequency operation by using it as an input interface for a single flux quantum (SFQ) logic circuit.