Electric Properties of Coplanar High- TCSuperconducting Field-Effect Devices

We have investigated coplanar superconducting field-effect devices, which consist of a YBa2Cu3OXthin film for the center channel and two side-gate electrodes, and a SrTiO3substrate as a gate insulator. Because of its simple structure, this device requires only a few steps in the fabrication process. We first simulated the electric-field distribution of the device by numerical calculation. The result indicated that significant current modulation was expected under 10 V gate voltage in this device. Based on the calculation, we fabricated the devices and measured their electric property, which showed 2%ICmodulation. Modulation showed a saturation characteristic, which resulted from the electric field dependence of dielectric constant of SrTiO3at low temperatures. This is the first observation of a superconducting field-effect device with a coplanar structure.