Vortex Flow Transistors Based on YBa_2Cu_3O^<7-δ> Films (Special lssue on Toward Digital and Analog Applications of Superconductors)

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We have studied the performances of several types of vortex flow transistors including prototype flux flow transistors (FFTs), nanobridge vortex flow transistors (NBVFTs) based on a parallel array of nanobridges, planar Josephson vortex flow transistors (planar JVFTs) based on a parallel array of grain boundary Josephson junctions, and JVFTs with a stacked structure (stacked JVFTs). The NBVFTs had considerably higher magnetic field sensitivity and shorter response time than the FFTs. A flux-to-voltage transfer function ∂V/∂Φ of 2.6 m V/Φ_0 and a modulation depth of 0.5 mV were obtained for the NBVFT composed of 2 nanobridges, while the current gain was small. The temperature dependence of the device parameters (the dynamic resistance and the inductance)suggests that the surface barrier to the Abrikosov vortex entry into the nanobridge strongly contributes to the relatively large∂V/∂Φvalues. The response time of the nanobridge is estimated to be 5 ps. On the other hand, the JVFTs showed large current gains because of the small kinetic inductance of the Josephson junction. The planar JVFT composed of 3 Josephson junctions with an asymmetrical geometry showed a current gain of 2.2 at 4.2 K. Also, the stacked JVFT showed the current gain of 2.0,while the maximum value of ∂V/∂Φwas 210μV/Φ_0. The mutual inductance between the control line and the superconducting loop within the transistor was enhanced in the stacked JVFT. This enhancement may yield a short response time compared to that of the planar JVFT. When we apply these vortex flow transistors, we should take account of the properties peculiar to each transistor.
社団法人電子情報通信学会の論文
1996-09-25

Vortex Flow Transistors Based on YBa_2Cu_3O^<7-δ> Films (Special lssue on Toward Digital and Analog Applications of Superconductors)

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