Current noise of contacts to YBa/sub 2/Cu/sub 3/O/sub 7/ high T/sub c/ superconducting platelets through the transition region

We describe noise measurements in the frequency range 10 Hz-1 MHz on indium contacts to YBCO layers with a LaAlO/sub 3/ substrate. The spectra are of the 1/f/sup /spl alpha// type with /spl alpha/=1.2 above T/sub c/ and 1.15 below T/sub c/. Above T/sub c/ there is burst noise, although the averaged spectra are stable and reproducible, The voltage noise versus temperature, for a fixed current, shows a sharp dip at the transition temperature T/sub c/=85 K, but is otherwise largely constant. The normalized noise S/sub v//V/sup 2/ goes as [R(T)]/sup -2/, which is indicative for 1D switching-percolation noise ("p-noise"), predicted previously, but not hitherto observed. This noise is of importance for low-frequency superconducting devices, such as bolometers and pyroelectric detectors, and for microwave devices where mixing with a carrier occurs. Current models of high T/sub c/ conductance-noise are reviewed and discussed.