Shapiro steps in large-area metallic-barrier Josephson junctions

The current amplitudes of Shapiro steps in large-area metallic-barrier Josephson junctions, both with and without a ground plane, are investigated with the goal of optimizing junction parameters for programmable voltage standards. Using the resistively shunted junction model without capacitance, we calculate maximum step amplitudes as a function of reduced frequency and junction dimension for both one- and two-dimensional junctions. For junctions without a ground plane, we conclude that step amplitudes of order 10 mA are practical, but significantly larger amplitudes require excessive microwave power.