CORRELATION OF CRITICAL-CURRENT AND RESISTANCE FLUCTUATIONS IN BICRYSTAL GRAIN-BOUNDARY JOSEPHSON-JUNCTIONS

We have performed a detailed analysis of the low frequency 1/f noise i n YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+x grain boundary Josephson junctio ns (GBJs) fabricated on SrTiO3 bicrystal substrates. The normalized fl uctuation of the critical current, delta I-c/I-c, and the normal resis tance, delta R(n)/R(n) were found to be almost independent of temperat ure and the misorientation angle. Furthermore, the magnitude of the fl uctuations is very similar for both high-T-c cuprates. Correlation exp eriments showed that the fluctuations of I-c and R(n) are anti-correla ted. Our analysis strongly suggests that the source of 1/f noise in hi gh-T-c bicrystal GBJs are localized defect states in an insulating gra in boundary barrier with fluctuating electron occupation. The effectiv e charge trapping time within single traps was found to decay exponent ially with increasing bias voltage. (C) 1995 American Institute of Phy sics.