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300 GHz Operation of Divider Circuits using High-Jc Nb/NbxSi1-x/Nb Josephson Junctions



David I. Olaya, Paul D. Dresselhaus, Samuel P. Benz


We are investigating high-current-density Josephson junctions with Nb(x)Si(1-x)-barriers in single- flux-quantum (SFQ) digital circuits to evaluate their performance at clock frequencies of hundreds of gigahertz. We fabricated static divider SFQ circuits with a- Nb(x)Si(1-x) and a-Si barriers for Jc ranging from 3.5kA/cm^2 to 85 kA/cm^2. For the lower Jc range (3.5 kA/cm^2 to 17 kA/cm^2) we used optical lithography, and for the 85 kA/cm^2 junctions we used e-beam lithography. We measured SFQ circuits with a maximum operating speed of 300 GHz by use of intrinsically shunted junctions having sub-micrometer dimensions and an 85 kA/cm^2 critical current density. These results demonstrate that silicide-barrier junctions have the potential to achieve high-speed SFQ circuits and higher density circuits because the junctions are small and don’t require external shunt resistors.
IEEE Transactions on Applied Superconductivity


Josephson junctions, Josephson devices, Josephson logic, Niobium, Superconducting devices, Superconducting device fabrication


Olaya, D. , Dresselhaus, P. and Benz, S. (2014), 300 GHz Operation of Divider Circuits using High-Jc Nb/NbxSi1-x/Nb Josephson Junctions, IEEE Transactions on Applied Superconductivity, [online], (Accessed April 20, 2024)
Created December 18, 2014, Updated November 10, 2018