BIEPITAXIAL JOSEPHSON-JUNCTIONS AND SUFET TECHNOLOGY FOR THE PREPARATION OF HTS-JOFETS

Biepitaxial Josephson junctions and superconducting field effect trans istors (SuFET) were fabricated in order to combine both techniques to a Josephson junction field effect transistor (JoFET). The Josephson ju nctions show RSJ-like behaviour. At 30 K a critical current density of J(c) almost-equal-to 10(4) A/cm2 and an I(c)R(N)-product of 0.1 mV we re obtained. The oscillation of Shapiro steps with applied microwave f ield can be well fitted by the RSJ-model. SuFETs with CeO2 as dielectr ic show, for fixed charge transfer, results comparable to SrTiO3-based SuFETs. The downset of the resistive transition of a six-unit-cells t hick YBa2Cu3O7-delta layer is 44 K and the largest field effect obtain ed so far is 1.5 %. Prelimary results on JoFETs show a drastic change in the critical current density and in the specific junction resistanc e, however the I(c)R(N)-product remains still in the typical range. Th e insulating properties are degraded compared to SuFETs.