Doped-type coplanar junctions in the Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8+/spl delta// system

We report on a vertical Josephson junction in the Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8+/spl delta// (BSCCO) system, based on a bilayer structure. A highly resistive bottom layer of Bi/sub 2/Sr/sub 2/(Ca/sub 1-z/Gd/sub z/)Cu/sub 2/O/sub 8+/spl delta// is deposited by DC-sputtering and covered by an undoped BSCCO layer with a T/sub c/ of typically 90 K. Junctions are formed by trenches patterned through the top layer into the resistive bottom layer. We found that the critical current I/sub c/ of the junctions is determined by the width of the grooves. Josephson coupling is demonstrated by Shapiro-like steps in the I-V curve up to a width of 0.8 /spl mu/m.