High-Tc ramp-type Josephson junctions on MgO substrates for terahertz applications

The authors successfully fabricated high-Tc ramp-type junctions with PrBa/sub 2/Cu/sub 3-x/Ga/sub x/O/sub 7-/spl delta// (PBCGO: x=0.1, 0.4) barriers on MgO substrates. The junctions showed resistively shunted Josephson junction (RSJ)-like I-V curves with thermally and voltage activated conductivity. The I/sub c/R/sub n/ products for these junctions scaled very well with the Ga-doping. Maximum response of the junctions for 100-GHz millimeter-wave irradiation could be observed up to 12 mV corresponding to 6 THz. Using far infrared laser radiation, we confirmed a terahertz (THz) response of these junctions. These results show promise for THz-wave applications of ramp-type Josephson junctions.