Introduction of ramp-type technology in HTS quasiparticle injection devices

Injection of quasiparticles with an energy larger than the superconducting gap into a superconducting strip results in breaking of Cooper-pairs and he nce the suppression of the superconducting properties. Experiments using pl anar injection devices made of HTS materials with various barrier materials showed current gains varying from 2 up to 15 at 77K. By changing the junct ion size and therefore the superconducting volume the current gain could be increased. A further reduction of the junction volume is very difficult us ing the planar de,ice geometry. However, by applying the ramp-type technolo gy it is possible to reduce the junction volume by at least one order of ma gnitude and a further increase in current gain is expected. Another advanta ge of this technology is the formation of in-situ barriers and electrodes a nd hence a better control of the junction characteristics should be possibl e, also the compatibility with the processes involved making RSFQ devices c an be interesting for later applications. We have fabricated ramp-type inje ction devices, using various types of barriers. Characterization of these d evices has been performed and the results of these experiments will be pres ented and discussed.