Observations in Use of a Tunnel Junction Model in Simulations of Josephson Digital Circuits

We have developed a microscopic tunneling Josephson junction compact model (TJM) framework and incorporated this in the Synopsys HSPICE commercial circuit simulator. Our model follows the Odintsov, Semenov, and Zorin (OSZ) approach, whereby tunnel current amplitude tables are reduced to a fitting parameter set, which is accessed by the simulator compact model. In addition, our model takes into account the computed BCS energy gap as a function of temperature and uses a table-lookup technique for rapid generation of temperature-specific parameters, enabling efficient temperature sweep and Monte-Carlo variation. This avoids the rather long computations required for generation of fit parameters for specific temperatures. Initially we will review the algorithms and features of our TJM model, then we will report simulation results of our model focusing on comparison to results using the standard RSJ model.