NbN and Nb SFQ device performance

The static frequency divider is commonly used as a performance benchmark for both superconductor and semiconductor digital device technologies. We present results of a static divide-by-two circuit, an NbN (1 kA/cm²) SFQ T-flip-flop (TFF) operating to 97 GHz. Details of the measurement and operating criterion are discussed. Measurements of junction capacitance, a particularly important factor effecting device performance, are presented for TRW´s NbN process. Simulations of expected device performance are shown to explain measured performance reasonably well. NbN results are presented alongside a those of a recent 8kA/cm² Nb divider operating at 300 GHz, as well as published Nb TFF results.