Fabrication of three terminal devices via a whole-wafer processing route

Using a whole-wafer route, the authors have fabricated high-quality three-terminal Nb(AlO_x)Nb(AlO_x)Nb devices with lead connections to each of the Nb layers, the middle Nb layer being on the order of 10 nm thick. A detailed description is presented of the adopted processing route, and recent results showing the junctions, independently biased, behaving as strongly coupled oscillators are discussed. The characteristics of the individual junctions show that the additional processing required to make the middle connection does not reduce the quality of the junctions. Preliminary results also show that the close proximity of the junctions possible with this route ensures strong inductive coupling (calculations for the present wafer dimensions give a coupling coefficient of 0.6) indicating its potential application in millimeter-wave coupling