NbSi Barrier Junctions Tuned for Metrological Applications up to 70 GHz: 20 V Arrays for Programmable Josephson Voltage Standards

PTB started using the robust NbxSi1-x barrier junction technology for the fabrication of large arrays for the Programmable Josephson Voltage Standard (PJVS) and for the Josephson Arbitrary Waveform Synthesizer 3 years ago. We demonstrate how Nb-doping of the amorphous Si barrier causes the transition from an underdamped to a desired overdamped junction behavior. Special dc SQUIDs have been used to evaluate junction capacitance and noise properties. The critical current of small junctions as a function of applied magnetic field has been investigated. On the basis of an existing 70 GHz design previously used for 10 V PJVS chips, we fabricated for the first time 20 V circuits with nearly 140 000 double-stacked Josephson junctions. A direct on-chip comparison between the two 10 V halves of the binary-divided array confirmed the metrological suitability of the 20 V circuits for dc and ac applications.

[1]  R. Dynes,et al.  Tunneling and Transport Measurements at the Metal-Insulator Transition of Amorphous Nb: Si , 1983 .

[2]  J. Kohlmann,et al.  SNS Junctions for AC Josephson Voltage Standards , 2012 .

[3]  J. Kohlmann,et al.  Improved 10 V SINIS Series Arrays for Applications in AC Voltage Metrology , 2007, IEEE Transactions on Applied Superconductivity.

[4]  Enhanced shot noise in resonant tunneling via interacting localized states. , 2003, Physical review letters.

[5]  B. I. Shklovskii.  1/f noise in variable range hopping conduction , 2003 .

[6]  M. Yu. Kupriyanov,et al.  Properties of planar Nb/α-Si/Nb Josephson junctions with various degrees of doping of the α-Si layer , 2012 .

[7]  David Olaya,et al.  Niobium-Silicide Junction Technology for Superconducting Digital Electronics , 2010, IEICE Trans. Electron..

[8]  S. Benz,et al.  10 Volt Programmable Josephson Voltage Standard Circuits Using NbSi-Barrier Junctions , 2011, IEEE Transactions on Applied Superconductivity.

[9]  G. A. Thomas,et al.  Metal-insulator transition in a doped semiconductor , 1983 .

[10]  M. R. Beasley,et al.  High-resistance SNS sandwich-type Josephson junctions , 1987 .

[11]  Ralf Behr,et al.  Development and metrological applications of Josephson arrays at PTB , 2012 .

[12]  Ralf Behr,et al.  Arrays with double-stacked NbxSi1-x-Barrier Junctions for Use in Programmable Josephson Voltage Standards driven at 70 GHz | NIST , 2009 .

[13]  B. Baek,et al.  Co-Sputtered Amorphous Nb$_{ x}$ Si$_{1 - { x}}$ Barriers for Josephson-Junction Circuits , 2006, IEEE Transactions on Applied Superconductivity.

[14]  S. P. Benz,et al.  1 V and 10 V SNS Programmable Voltage Standards for 70 GHz , 2009, IEEE Transactions on Applied Superconductivity.

[15]  L. Smith,et al.  Improved Nb-Si-Nb SNAP devices , 1983 .

[16]  K. Likharev,et al.  Dynamics of Josephson Junctions and Circuits , 1986 .

[17]  J. Magerlein,et al.  Specific capacitance of Josephson tunnel junctions , 1981 .

[18]  H. Huggins,et al.  High quality refractory Josephson tunnel junctions utilizing thin aluminum layers , 1983 .

[19]  I. F. Quercia.  Physics and applications of the Josephson effect , 1984 .

[20]  P.D. Dresselhaus,et al.  Design of SNS Josephson Arrays for High Voltage Applications , 2007, IEEE Transactions on Applied Superconductivity.