Andreev reflection at superconducting contacts to GaAs/AlGaAs heterostructures

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Abstract
Highly transmissive ohmic contacts to the two‐dimensional electron gas in GaAs/AlGaAs heterostructures have been made. For these contacts, which are of μm scale, a newly developed process of Ti/Sn evaporation and diffusion has been used. Devices consisting of these superconducting contacts combined with gate structures have shown clear evidence for the occurrence of Andreev reflection. Moreover a marked effect of the gate voltage on the dV/dI−V characteristics has been found, which proves that superconductivity has been induced into the semiconductor.