HOT-ELECTRON QUASI-OPTICAL NBN SUPERCONDUCTING MIXER

Hot electron superconductor mixer devices made of thin NbN films on Si O2-Si3N4-Si membrane have been fabricated for 300-350 GHz operation. T he device consists of 5-10 parallel strips each 5 mu m long by 1 mu m wide and are coupled to a tapered slot-line antenna The IV characteris tics and position of optimum bias point were studied in the temperatur e range 4.5-8 K. The performance of the mixer at higher temperatures i s closer to that predicted by theory for uniform electron heating. The intermediate frequency bandwidth versus bias has also been investigat ed At the operating temperature 4.2 K a bandwidth as wide as 0.8 GHz h as been measured for a mixer male of 6 nm thick film. The bandwidth te nds to increase with operating temperature. The performance of NbN mix er is expected to be better for higher frequencies where the absorptio n of radiation should be more uniform.