Improving the Josephson energy in high-Tc superconducting junctions for ultra-fast electronics

We report the electrical transport of thin vertically-stacked Josephson tunnel junctions. The devices were fabricated using 16 nm thick GdBa₂Cu₃O_7-δ electrodes and 1-4 nm SrTiO₃ as an insulating barrier. The results show Josephson coupling for junctions with SrTiO₃ barriers of 1 and 2 nm. Subtracting the residual current in the Fraunhofer patterns, energies of 3.1 mV and 5.7 mV at 12 K are obtained for STO barriers of 1 nm and 2 nm, respectively. The residual current may be related to the contribution of pinholes and thickness fluctuations in the STO barrier. These values are promising for reducing the influence of thermal noise and increasing the frequency operation rate in superconducting devices using high-temperature superconductors.