Room-temperature testing for high critical-current-density Josephson junctions

Abstract

Abstract-This paper demonstrates that room-temperature resistance measurements can accurately predict the critical current and normal resistance of high critical-current-density junctions. We fabricated high critical-current-density ( 200 A/ m 2 = 20 kA/cm 2 ) Nb/Al/AlO /Nb Josephson junctions in cross-bridge Kelvin resistor (CBKR) test structures and measured their electrical characteristics both at 4.2 K and at room temperature. We developed a two-dimensional mathematical model of the CBKR test structure with two resistive wiring layers in order to characterize the effect of current crowding on the room-temperature measurements. We then used the model to remove the effect of current crowding from the room-temperature measurements and correlated the values of these measurements to the electrical properties of the junctions at 4.2 K. We also identified test-structure-design rules that guarantee current crowding is negligible.

Fabrication and room temperature characterization of trilayer junctions for the development of superconducting qubits on 300 mm wafers

“…Vias were measured having a negligibly small resistance of only ∼1 Ω. For simplicity, the following results will focus on 4-probe measurements of JJs in the cross-bridge Kelvin resistor (CBKR) geometry 38) pictured in Figs. 5(d) and 5(e).…”