The main parameters of the tunneling barrier of the Josephson junctions Nb/AlO_x/Nb and Nb/AlN/Nb were estimated using the Simmons method in a wide range of current densities. The dependences of the height and width of the tunnel barrier on the resistivity for each type of junctions are experimentally determined. A decrease in the height of the AlN tunnel barrier by 0.3 eV, compared with the oxide one, makes it possible to obtain junctions with a current density above 15 kA/cm² at a technologically achievable insulation layer of the order of 10 Angstroms, which makes it possible to realize the quality parameter R_j/R_n not lower than 25.

The technology for manufacturing submicron Nb - AlN - NbN tunnel junctions using electron beam lithography has been developed and optimized. Investigations have been carried out to select the exposure dose, development time, and plasma-chemical etching parameters to obtain the high quality of junctions (the ratio of the resistances below and above the gap Rj/Rn). The use of a negative resist ma-N 2400 with lower sensitivity and better contrast in comparison with a negative resist UVN 2300-0.5 has improved the reproducibility of the structure fabrication process. The submicron (area from 2.0 to 0.2 µm2) tunnel junctions Nb - AlN - NbN with high current density and quality parameter Rj / Rn> 15 were fabricated. The spread of parameters of submicron tunnel structures across the substrate and the reproducibility of the cycle-to-cycle process of fabrication of tunnel structures has been experimentally measured.

The issues of designing a Josephson traveling-wave parametric amplifier (JTWPA) based on a well-established technology of superconducting microcircuits with given and controlled parameters based on high-quality Nb-AlOx-Nb tunnel junctions are considered. This technology has been adapted and optimized to obtain structures with the required parameters and circuits with large number of tunnel junctions. To advance the technology, the basic elements of a promising JTWPA have been devel-oped, manufactured and studied. In direct current measurements, a number of super-conducting elements parameters were experimentally determined; these parameters are required for designing a JTWPA chips for microwave measurements. An original design of JTWPA based on a chain of SQUIDs in a coplanar line has been developed for implementation using the IRE niobium technology; the parameters of the main elements of the JTWPA have been determined.

This work is devoted to the study of tunnel Josephson superconductor-insulator-superconductor (SIS) junctions with a new type of shunting based on the usage of an additional superconductor-insulator-normal metal (NIS) junction located around the SIS junction. Numerical calculations of the parameters of such shunted junctions were carried out and modeling of their IVC (current-voltage characteristics) was performed. The designed samples were manufactured, their parameters were studied. To investigate the behavior of junctions under the influence of high-frequency signals in the sub-THz range, their IVCs were measured.