Bit error rate experiments with RSFQ circuits realized in SINIS technology

The paper reports on the development of ring-shaped rapid single flux quantum (RSFQ) circuits fabricated in superconductor-insulator-normal metal-insulator-superconductor Nb/AlxOy/Al/AlxOy/Nb technology. The circuits enable the generation and maintenance of permanent SFQ pulse circulation and the bit error rate (BER) of test circuits to be determined experimentally. Various ring structures comprising switching circuits of several stages have been realized. A single switching stage consists of an escape junction and is fed by a separate bias current to adjust the threshold level of this junction. The reliability of circuit operation has been experimentally proven by BER < 10(-15). The critical current densities of the junctions are in the range j(C) congruent to 450-750 A/cm(2) and the characteristic voltage is about V-C = 170 muV. (C) 2002 Elsevier Science B.V. All rights reserved.