YBa2Cu3Ox Josephson junctions on a bicrystal sapphire substrate for devices in the millimeter and submillimeter wavelength ranges

High-temperature superconducting Josephson junctions on bicrystal sapphire substrates were fabricated and investigated experimentally. The critical parameters of the junctions satisfy the constraints for the design of devices in the millimeter and submillimeter wavelength ranges. The results of dynamic measurements show that in these junctions the superconducting current exhibits a sinusoidal dependence on the phase difference of the superconducting wave functions of the electrodes, and a simple resistive model is used to analyze their microwave properties. At the same time, the temperature dependence of the critical current of the junctions differs appreciably from that typical of tunnel junctions with s-superconductors and may be explained as d-type pairing of the superconducting electrodes and an SNS junction. Pis’ma Zh. Tekh. Fiz. 25, 1–8 (April 12, 1999)