Quasi-particle injection devices for interfaces between superconductors and semiconductors

We have fabricated an injection type 3-terminal device for interface between superconductor and semiconductor circuits using a high temperature superconductor. When quasi-particles are injected from the Au electrode to a YBa₂Cu₃O_7-x (YBCO) bridge, superconductivity of the bridge area is weakened and I_c of the bridge decreases. Therefore, we can easily make the bridge in resistive state by injecting sufficient amount of current I_inj . The length, width, and thickness of the bridge are 20 μm, 10 μm, and 100 nm, respectively. The Au-YBCO contact area is 200 μm ². When the bridge became resistive, the resistance was about 100 Ω. The current gain |ΔI_c/ΔI_inj| was as high as 9. However, the contact resistance was about 17 Ω, which is 200 times as large as the required value for the operation as an interface device. This shortcoming might be overcome by appropriate annealing