SBIR-STTR Award

this project, Hypres, Inc. Will fabricate thin-film transistors out of high temperature superconductors. In this transistor-like device, one inputs a current, which controls a magnetic field. When the initial current crosses magnetic lines of flux, this creates individual circulating currents. Several of these currents can move through weak superconductors, altering the rate of nucleation of vortices. This in turn controls the device's resistance, thereby controlling the output. Vortex-flow transistors offer low input impedance--much lower than semiconductors. And they require less power. Further, they produce a large voltage output swing: from 0 to 50 millivolts, compared to only 0 to 3 millivolts for a typical josephson junction. This large voltage output swing makes it easier to drive a semiconductor. Vortex-flow transistors can connect low temperature (lt) superconducting devices, such as josephson junctions, to room temperature (rt) semi-conductors. Vortex-flow transistors can operate at or above 77 k, allowing the use of liquid nitrogen cooling, which is far less costly than coolants for lt superconductors. This device permits the development of hybrid digital electronics, which incorporates both lt superconductors and digital electronics in one device, making possible faster readouts, such as in a/d converters. The new transistors can also serve in phase shifters, oscillators, amplifiers, and even digital logic circuits.

Project originally made to HYPRES in NY state but with the same PI. The superconducting flux flow transistor appears to be a promising candidate for active high temperature ceramic thin film circuits. The SFFT has potential applications in interfaces between digital Josephson Junction electronics with semiconductor circuits, for example. Oscillation at frequencies up to 7.5 GHz was observed, single and multi-stage amplifiers have been designed and built. Mixing at 35 GHz has been shown. Dual gate SFFT devices have been designed, fabricated and tested. Phase shifters with 200 series SFFTs produced linear phase shift with control current. We propose to evaluate the applicability of SFFT devices to monolithic microwave oscillators, high gain stages in conjunction with Josephson vortex flow transistors and interfaces between digital Josephson circuitry and room temperature electronics. Prototype circuits will be fabricated and tested. We will also investigate alternate fabrication methods.