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 YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) bridge, superconductivity of the bridge area is weakened and I/sub c/ of the bridge decreases. Therefore, we can easily make the bridge in resistive state by injecting sufficient amount of current I/sub inj/. The length, width, and thickness of the bridge are 20 /spl mu/m, 10 /spl mu/m, and 100 nm, respectively. The Au-YBCO contact area is 200 /spl mu/m/sup 2/. When the bridge became resistive, the resistance was about 100 /spl Omega/. The current gain |/spl Delta/I/sub c///spl Delta/I/sub inj|/ was as high as 9. However, the contact resistance was about 17 /spl Omega/, 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.