Self-shunted Nb/AlOx/Nb Josephson junctions

We describe the fabrication and properties of high critical current density (J(c)) Nb/AlOx/Nb Josephson junctions with deep-submicron dimensions. The junctions are fabricated using a planarized process in which all levels are patterned using a combination of optical and electron-beam lithography. The base and counter electrodes are defined by reactive ion etching using quartz etch masks to give a minimum feature size of 0.2 microns. For J(c) = 2.1 mA/mu m(2) and junction area less than 0.1 mu m(2) the devices are self-shunted and exhibit nonhysteretic IV characteristics. A small hysteresis in the larger junctions is caused by heating in the electrodes.