Stationary properties of SINIS double-barrier Josephson junctions

Abstract

This paper reports on the evaluation of the effective suppression parameter γ eff in double-barrier Josephson junctions realized in Nb-Al/Al x O y /Al/Al x O y /Al-Nb SINIS technology. This parameter describes the overall resistance of current flow across the interfaces within the whole structure configuration and characterizes its I C R N product attainable. By comparison with theoretical descriptions of tunnelling structures in the dirty-limit approximation, the effective suppression parameter γ eff has been extracted from the measured temperature dependence of the I C R N product. For SINIS junctions of a series of different wafer productions with various critical currents of the fabricated junctions, the evaluated values of γ eff range between 80 and 250. With reference to the proximity effect and to the possibility of removing the Al layers at the Nb electrodes, a value of γ eff has been deduced, which ranges between 50 and 120. This is very close to the assigned value between 10 and 20 ideally suitable for integrated circuit applications, e.g. Josephson voltage standards and rapid single flux quantum circuits.

Microscopic nonequilibrium theory of double-barrier Josephson junctions

“…The experimental observation that the hysteresis in the IV curves depends nonmonotonically on the critical current density has not yet been explained. 26,27 Thus, understanding the transport properties on a microscopic level will be valuable for electronic applications. Here, these transport phenomena will be clarified in terms of the opening of Andreev channels and inelastic scattering in the interlayer.…”

Current-phase relation in Nb-Al based SINIS-type Josephson junctions

“…Despite of the lower quality factor, the use of a normal metal coil ( cffectivc suppression parameter which is closely related to the barrier transparency. In the case of sufficiently small critical current density as investigated here, it is automatically much higher than unity [15].…”

Properties of planar Nb/α-Si/Nb Josephson junctions with various degrees of doping of the α-Si layer

“…4-7, the shape of CVC changes substantially with the impurity concentration in the α Si layer: as the tungsten con centration decreases, it transforms from the CVC of a classical SNS junction to the curves typical of two barrier Josephson structures [9][10][11][12]44]. This change can only be explained by another current transport mechanism, which dominates over both the mecha nism of direct current passage through the N layer and direct electron tunneling through the layer.…”

“…The barriers in all materials were formed by the oxidation of aluminum. The substantial difference in the mor phologies of an Al film on an S electrode and the film located between dielectric layers makes it possible to achieve the required symmetry only in the case of low transparency barriers [10][11][12][13][14].…”