NOVEL HYBRID NB INAS NB STEP JUNCTIONS

We present experimental results for novel superconductor/semiconductor heterostructure hybrid systems, which rely on the use of the two-dime nsional electron gas at the surface of p-type InAs. The surface channe l is made in an InAs step between Nb contacts. Such a geometry allows fabrication of short weak links (approximate to 100 nm) as well as rea lization of a variety of heterostructure potential profiles along the channel since the latter is oriented perpendicular to the growth direc tion of the heterostructure. By measuring the current-voltage characte ristics at 4.2 K, we observe supercurrent, subharmonic gap, structure, as well as above gap structure and excess current. The junction trans parency is estimated to exceed 70%.