Title :
Rapid single flux quantum T-flip flop operating up to 770 GHz
Author :
Chen, W. ; Rylyakov, A.V. ; Patel, V. ; Lukens, J.E. ; Likharev, K.K.
Author_Institution :
Dept. of Phys. & Astron., State Univ. of New York, Stony Brook, NY, USA
fDate :
6/1/1999 12:00:00 AM
Abstract :
Rapid Single Flux Quantum (RSFQ) T-flip flops (TFFs) operating up to 770 GHz have been demonstrated at 4.2 K. The devices, consisting of either resistively shunted or unshunted Josephson junctions, are fabricated using a planarized Nb/AlO/sub x//Nb trilayer process. Electron beam lithography is used to pattern all levels with a minimum junction area less than 0.1 /spl mu/m/sup 2/. Critical current densities of 0.5 mA//spl mu/m/sup 2/ and 2.5 mA//spl mu/m/sup 2/ are used for the shunted (tested at 1.8 K) and unshunted devices (tested at 4.2 K) respectively. The input and output frequencies of the TFFs are obtained from the input and output voltages by the Josephson relation. The output voltage is exactly half of the input voltage when the divide-by-two operation is correct.
Keywords :
aluminium compounds; critical current density (superconductivity); electron beam lithography; flip-flops; niobium; superconducting logic circuits; superconductor-insulator-superconductor devices; very high speed integrated circuits; 4.2 K; 770 GHz; Josephson relation; Nb-AlO-Nb; critical current densities; divide-by-two operation; electron beam lithography; input frequencies; input voltage; output frequencies; output voltage; planarized Nb/AlO/sub x//Nb trilayer process; rapid single flux quantum T-flip flop; resistively shunted Josephson junctions; superconducting digital circuits; unshunted Josephson junctions; Circuits; Critical current; Critical current density; Frequency; Josephson junctions; Niobium; Pulse generation; Resistors; Testing; Voltage;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
