IF bandwidth and noise temperature measurements of NbNHEB mixers on MgO substrates

We report the fabrication and testing of hot electron bolometric mixers wit h an ultrathin NbN film as heterodyne receivers operating at the terahertz frequencies. We found that the qualities of NbN strip are usually degraded by the damages resulting from fabrication process, We have developed a fabr ication process for reducing the damages in NbN films. We also fabricated H EB mixers with a new structure In order to study the IF bandwidth determine d by the original qualities of NbN thin films, Investigations at 100 GHz re vealed that the widest IF bandwidth of 2.0 GHz was obtained by a mixer base d on 2.8 nm-thick NbN film An usual type of HEB mixer based on the 2.8 nm-t hick NbN film was also fabricated and evaluated. The receiver noise tempera ture at 900 GHz was 780 K, the absorbed LO power was about 400 nW, and the conversion gain was -13 db.