Superconducting contacts to a two-dimensional electron gas in GaAs/AlGaAs-heterostructures

The process of Sn/Ti-diffusion is shown to provide low-resistance (highly transmissive) contacts to the two-dimensional electron gas (2DEG) in GaAs/AlGaAs-heterostructures. At temperatures down to 80 mK the resistance stays very low. The temperature and gate-voltage dependence of the dV/dl-V-curves shows that Andreev reflection must take place in the sample. The measurements suggest that Ti is the relevant superconductor and not Sn. The fact that the bottom of the low-resistance region is very flat and does not show a peak near V=0 V means that the transmission of the NS (normal metal-superconductor) interface is very close to 1. Therefore these superconducting contacts seem to be very suitable for studying SNS (superconductor-normal metal-superconductor) junctions in the clean limit.<
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