Josephson device with tunneling barrier having low density of localized states and enhanced figures of merit

摘要

A superconducting tunnel junction device having superconductive electrodes has a non-homogeneous barrier layer of amorphous semiconductive material, wherein when the central region is deposited in the presence of a gaseous atmosphere containing hydrogen there obtains a reduced density of localized states in the central region of the barrier so as to minimize leakage currents, resulting in improved current-voltage characteristics approximating an ideal tunnel junction device. The low leakage currents improve margins of Josephson logic circuits over tunneling barriers using uniformly deposited hydrogenated silicon with niobium electrodes, and increase the sensitivity of S-I-S microwave and millimeter wave length detectors and mixers. In a preferred embodiment, superconductive electrodes of niobium are conjoined with a tri-layer barrier using pure silicon adjoining the electrodes and a core of hydrogenated amorphous silicon. V.sub.m parameters of merit (product of subgap resistance and critical current) as high as 28 mV at 4.2K were obtained with this embodiment, compared with 10 mV for the prior art.