Abstract
Experimental results for novel superconductor/semiconductor hybrid systems are presented. The junctions have a step-like geometry, employing two Nb electrodes which are evaporated onto a step that is etched in InAs. Such a geometry allows one to fabricate short weak links (approximately 200nm) as well as to realize a variety of heterostructure potential profiles along the channel between the superconducting electrodes, since this channel is oriented parallel to the growth direction of the heterostructure. Different semiconductor heterostructures, such as low p-doped InAs, whose native surface inversion layer has the character of a two-dimensional electron gas (2DEG), or npn-InAs heterostructures, where th 2DEG of a thin (150nm) p-layer is sandwiched between two n-InAs layers, are used. By measuring the currentvoltage characteristics at 4.2K, supercurrents, subharmonic gap structures, as well as excess currents, are observed.
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