Influence of La-doping of YBa2Cu3O7 on transport properties of interface-engineered ramp-edge junctions

We have investigated the influence of La-doping of the YBa2-xLaxCu3O7 (YBCO ) thin film electrodes on de and sc Josephson properties of ramp-edge junct ions with interface-engineered barriers. Non-doped optimized junctions exhi bit critical current densities, j(c), of 5 . 10(4) A/cm(2) and normal sheet properties of junctions with x=0.03 La-doping are quite similar to those o f non-doped junctions. La-doping of x = 0.05 and x = 0.07 leads to an incre ase of R-N.A and decrease of jc by about one order of magnitude. Devices wi th jc < 10(4) A/cm(2), which are operating in the short junction limit exhi bit current-voltage characteristics without any excess current and 100 % mo dulation of critical current in external magnetic field, The current voltag e characteristics exhibit well defined Shapiro steps. The dependence of cur rent-step height on microwave current can be described in the resistively-s hunted junction properties of the junctions with and without doping. model. The strong changes in the temperature dependencies of j(c) and R-N.A sugge st different electrical transport properties for junctions, interface engin eering junctions fabricated with non-doped and La-doped YBCO. The temperatu re dependence of the critical current and the normal resistance allows us t o draw conclusions to the transport properties of our junctions.