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 YBa2Cu3O7-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 mum, 10 mum, and 100 nm, respectively. The Au-YBCO contact area is 200 mum(2). When the bridge became resistive, the resistance was about 100 Omega. The current gain \ DeltaI(c) / DeltaI(inj)\ was as high as g. However, the contact resistance was about 17 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.