KA-BAND PERFORMANCE OF STEP-EDGE JOSEPHSON-JUNCTIONS USING TL2BA2CACU2OX FILMS ON MGO SUBSTRATES

Tl2Ba2CaCu2Ox (Tl-2212) step-edge Josephson junctions (SEJJs) on MgO s ubstrates have been fabricated and tested for millimeter wave applicat ions. Although the single SEJJs exhibited clear Shapiro steps under Ka -band (27 to 40 GHz) irradiation and a Fraunhofer-like pattern under a magnetic field, their responsivities as Ka-band detectors were too sm all to construct a mixing device. This is due to their small normal re sistance (R(n)) of 0.2 to 0.9 Omega, which determines the impedance ma tching for the microstrip signal lines. Therefore, series-connected si x SEIJs (6-SEJJs) have also been fabricated to improve the impedance m atching. Their responsivities are 2-3 orders of magnitude larger than those of single SEJJs. Furthermore, efficient IF (intermediate frequen cy) output of fundamental mixing with low LO (local oscillation) power of a few mu W is observed up to 95 K.