Quasiparticle trapping in distributed three-terminal double tunnel devices (particle detectors)

Devices of the structure S/sub 1/IS/sub 2/S/sub 1/S/sub 2/IS/sub 1/ have been fabricated in which the common S/sub 1/ layer is an epitaxially grown Nb base electrode and S/sub 2/ is Ta. By strongly biasing one junction a nonequilibrium distribution of quasi-particles is established in the Nb base. These quasi-particles may be detected by the other junction which is biased in the subgap region. Quasi-particle multiplication in the Nb and Ta layers has been observed. Quasi-particle trapping, in which quasi-particles are confined to the Ta layer adjacent to the barrier, has been shown to be an effective method of increasing the detected current.<>