A number of new fabrication techniques are developed and optimized in order to fit the requirements of contemporary superconducting electronics. To achieve ultimate performance of integrated submm receivers with operational frequency of 1 THz, tunnel junctions with AlN tunnel barrier having a value as low as 1 m 2 have been developed. High quality characteristics of Nb/AlN/Nb tunnel junctions with = 16 and = 10 m 2 have been demonstrated. Electron Beam Lithography (EBL) in combination with Chemical Mechanical Polishing (CMP) has been incorporated to produce Nb/AlN/Nb junctions with 0.03 m 2 area. A new approach to get overdamped Nb/AlO /Nb tunnel junction has been proposed and realized. The dependencies of the main parameters of novel junctions on the currents density and circuits geometry have been studied. These junctions may have a good potential in Josephson Junction Arrays and Single-Flux-Quantum applications (RSFQ).

A low-noise rf amplifier based on a dc SQUID (SQA) has been tested in the frequency range 3.0-4.6 GHz in the open-loop configuration. The following parameters have been measured for the single-stage balanced type SQA at 4.0 GHz: gain (12 1) dB, 3 dB bandwidth of 500 MHz and noise temperature (1 0 0 25) K. For the nonbalanced type SQA at 4.0 GHz gain was (15 1) dB, 3 dB bandwidth 200 MHz and noise temperature (0 5 0 25) K. The improved performance is obtained due to the increased characteristic voltage ( 420 V) of the small-area (down to 0.7-0.9 m 2 ) high-quality Nb-AlO -Nb SIS junctions. The saturation power (normalized to 1 GHz) referred to the input at 1 dB gain compression is estimated as 55 K*GHz at a bias voltage of 60 V. The reasons for saturation of the SQA are discussed.

No abstract

No abstract

No abstract