SUPERCONDUCTING FIELD-EFFECT DEVICES WITH HIGH TRANSITION-TEMPERATUREAND CRITICAL-CURRENT DENSITY

We have investigated buffer layers of (Pr0.55Y0.45Ba2Cu3O7-delta (PY)B CO for YBa2Cu3O7-delta (YBCO)/SrTiO3 field effect devices. The transit ions of single unit cell thick YBCO films in (PY)BCO/YBCO/(PY)BCO tril ayers depend strongly on the buffer layer thickness, with optimum T-c approximate to 40 K obtained at a buffer layer thickness of 5 nm. SuFE T devices deposited on such an optimized buffer layer exhibit substant ial improvements in channel quality. For a 3.6 nm thick channel, trans ition temperature >55 K and critical current density similar to 10(6) A/cm(2) are obtained. The modulations observed in both the normal and superconducting states are consistent with those obtained in earlier w ork on non-weak-link dominated samples.