Low noise Nb-based SIS mixer for sub-millimeter wave detection Original Research Article

The Nb-based SIS junction fabrication was started in 1996. The main goals of this project are to establish the capability of high quality SIS junction technology in Taiwan and to fabricate SIS mixer for sub-millimeter wave detection. In the past few years, we have integrated the fabricating facility and processing steps. The self-alignment method was used for junction definition process. The junction size is close to 1 μm in order to minimize its intrinsic capacitance. The critical current density is required to be ≧7.5 kA/cm2 to get a reasonable ωRnC product of the mixer. The high quality SIS junction was demonstrated from its I–V characteristics. We also fabricated 230 and 350 GHz SIS mixers. The performance test of the mixer shows a low noise temperature level. The details of the mixer fabrication process and performance test will be described in this paper.