Nb-Al-Al/sub 2/O/sub 3/-Nb junctions with inductive tuning elements for a very low noise 205-250 GHz heterodyne receiver

摘要

The authors have developed a Nb-Al-Al/sub 2/O/sub 3/-Nb junction fabrication process which allows the use of planar tuning circuits integrated with the junctions. These tuning elements permit the use of junctions with relatively large areas and small current densities with excellent results. Recent measurements have yielded a double sideband receiver noise temperature of less than 50 K from 205 to 240 GHz and 44 K at 230 GHz. The Nb-Al-Al/sub 2/O/sub 3/-Nb trilayer technology is being extended to the fabrication of sub-square-micron-area planar junctions for submillimeter wavelengths.