Niobium Superconducting Tunnel Junction Terahertz Detectors Directly

Since the1980s, Terahertz(Thz) science and technology have been breaking through the bottleneck of sources and detectors gradually, and developed rapidly. Scientists all over the world have been striving for this new electromagnetic resource. At the same time, the major breakthrough of fabrication of superconducting tunnel junction(STJ) promoted the development of superconducting electronics. Under this scientific background, we designed, prepared and tested THz direct detectors with Nb-based STJs. In this thesis, we focus on these issues as following:ⅰ. We propose a new analytical approach to find possible junction configuration from all parameter space, and then establish a design method of these distributed junction arrays.ⅱ. According to the requirement of the THz direct detectors and the existing equipment and conditions in our laboratory, we developed the fabrication process of Nb/AI/AlOx/AI/Nb, including LOR lift-off, SNEP and so on.ⅲ. The leakage current per unit area and per unit perimeter indicate the leakage current comes from barrier layer. Therefore, we find the optimized parameters for high quality of Nb STJ by systematically analyzing the thin film stress, surface morphology and modified junction structures.ⅳ. In order to reduce the measurement system noise, we propose a concept of integration of the THz direct detector with Nb STJs and the cryogenic readout with GaAs JFETs.ⅴ. Finally, the detectors were measured at0.3K, and the quasiparticle steps on its I-V cureve implied the good response to650GHz irradiation. The leakage current at1mV is about100nA, and NEP is about10-15W/Hz1/2...