Introduction to S.I.S.

Superconductor-Insulator-Superconductor (S.I.S.) tunnel junctions are made for use as terahertz mixers, intended for application as detectors in radio telescopes. S.I.S. devices are much more sensitive than conventional GaAs Schottky diodes,acting like very good diodes with millivolt turn-on voltages. They require cooling to around the nine degree Kelvin region to work, but the net benefit in performance offsets the cost of cooling.

S.I.S. devices are typically made using Niobium (Nb),a refractory metal that exhibits superconductor behavior at around nine degrees Kelvin.

Our S.I.S. devices were fabricated at AMC and tested in our R.A. lab, either by Liquid Helium dipping or with a CTI cryostat mounted multiple four point probe apparatus originally designed by Dr. Graham Walker. Test results of two good devices with transitions to the super conducting region at 12 and 13.5 degrees Kelvin are available here. The test was done with the apparatus mounted on the second stage of our CTI 1 watt cryostat.