Microwave application of three-terminal Josephson device under hot quasiparticle injection

New effects of quasiparticle injection on microwave-irradiated Josephson triodes are demonstrated. The device comprises Pb-insulator (Nb2O5)-Nb SIS junction with direct contact of the Nb film to n(+)-GaAs gate substrate. In this device, the very thin Nb film (300-600 A) used as a base electrode of the SIS detector also serves as an acceptor of the quasiparticles injected from GaAs-Nb Schottky barrier. The emphasis is placed on injections of hot quasiparticles with the energy in excess of 0.5 eV. The zeroeth step height of microwave (10 GHz) irradiated Josephson current I(o) was efficiently modulated by a sufficiently low density quasiparticle injection current of 1-2 A/sq cm, though no sign of change was found in the superconductive gap parameter and the Josephson critical current itself. These characteristic features become less pronounced as the energy of injected quasiparticles was reduced to below 50 meV. Though the present experiment is in a preliminary stage, a current amplification of higher than two has been attained on a test specimen.