Operation of single-flux-quantum logic cells based on all-NbN integrated circuit technology

摘要

We developed NbN-based SFQ circuits consisting of high-quality epitaxial NbN/AlN/NbN trilayer grown on MgO (100) substrate. The SFQ logic cells such as JTL, DC/SFQ converter, voltage driver, pulse splitter, TFF, and CB were designed by setting the critical current density JC at 2.5 kA/cm². We succeeded in demonstrating correct operations of all the designed SFQ cells, but the JC range allowing the operation was quite narrow as around 70% for the designed value. The circuit simulation revealed that the TFF cell requires the JC range from 65% to 115% for the correct operation, while the DC/SFQ converter was not operational for the JC of more than 70%.