Title :
High current density NbN/AlN/NbN tunnel junctions for submillimeter wave SIS mixers
Author :
Wang, Z. ; Uzawa, Y. ; Kawakami, A.
Author_Institution :
Kansai Adv. Res. Center, Commun. Res. Lab., Kobe, Japan
fDate :
6/1/1997 12:00:00 AM
Abstract :
We report on the fabrication and properties of high current density NbN/AlN/NbN tunnel junctions for the application of superconducting SIS mixers in the submillimeter wave regions. Junctions having current densities as high as 50 kA/cm/sup 2/ exhibited a good Josephson tunneling behaviour, excellent terahertz response, and sensitive heterodyne mixing properties. Accurate values of junction capacitance were estimated by measuring dc-SQUID resonant steps for the design of tuning circuits. The measured specific capacitance gives values in the range of 20-200 fF//spl mu/m/sup 2/ for the current density range of 1-100 kA/cm/sup 2/. The NbN/AlN/NbN tunnel junctions were integrated with a NbN thin film antenna to investigate the terahertz responses and mixing tests in a quasi-optical testing system. Photon-assisted tunneling steps were clearly observed on the I-V curve with irradiation up to 1.02 THz, and a low-noise heterodyne mixing was demonstrated in the 300-GHz band.
Keywords :
aluminium compounds; current density; niobium compounds; submillimetre wave mixers; superconductive tunnelling; superconductor-insulator-superconductor mixers; 1.02 THz; 300 GHz; DC-SQUID resonant steps; I-V characteristics; Josephson tunneling; NbN thin film antenna; NbN-AlN-NbN; NbN/AlN/NbN tunnel junction; current density; heterodyne mixing; photon-assisted tunneling; quasi-optical testing; specific capacitance; submillimeter wave SIS mixer; terahertz response; tuning circuit; Capacitance measurement; Circuit optimization; Current density; Fabrication; Josephson junctions; Resonance; Submillimeter wave circuits; Superconducting devices; System testing; Tunneling;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
