Silicon-barrier Josephson junctions in coplanar and sandwich configurations

Recent considerations on sandwich-type crystalline-silicon-barrier Josephson junctions are given. We show how low-shunt-capacitance electrode configurations can be realized on the thin silicon membranes. As an extension of our work on sandwich-type silicon-barrier devices, we have fabricated junctions with coplanar electrodes separated by a narrow gap on a highly doped silicon surface. These show supercurrents in the range of 1-10 mA for gaps in the range of 0.1-0.3 μm in a strip of 30 μm width and a surface doping of about 2 × 10²⁰cm^-3. In both structures, small changes can be made to obtain the behavior of a super-Schottky diode rather than a Josephson junction. These diodes are found to have high sensitivities (S=2000 to 2300 V^-1) and can be designed to have low series resistance.