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

The Nb-based SIS junction fabrication was started in 1996. The main goals o f this project are to establish the capability of high quality SIS junction technology in Taiwan and to fabricate SIS mixer for sub-millimeter wave de tection. In the past few years, we have integrated the fabricating facility and processing steps. The self-alignment method was used for junction defi nition process. The junction size is close to 1 mum in order to minimize it s intrinsic capacitance. The critical current density is required to be gre ater than or equal to 7.5 kA/cm(2) to get a reasonable omegaR(n)C product o f the mixer. The high quality SIS junction was demonstrated from its I-V ch aracteristics. We also fabricated 230 and 350 GHz SIS mixers. The performan ce test of the mixer shows a low noise temperature level. The details of th e mixer fabrication process and performance test will be described in this paper. (C) 2001 Elsevier Science Ltd. All rights reserved.