A reproducible process for mesoscopic superconducting indium contacts to GaAs/AlGaAs heterostructures

In this report we present a procedure to fabricate high transmissive superconducting (S) contacts by diffusing indium into $GaAs/AlxGa1−xAs$ based high-mobility two-dimensional electron gas (2DEG). We use a thermostable trilayer resist for indium lift-off. By doing electrical measurements at low temperature and transmission electronic microscopy observations, we show that the current through the S/2DEG interface is carried by a few number of localized indium filaments providing a good contact with the 2DEG. The low dimensional nature of those filaments is characterized by phase slip centers in the $I(V)$ curve of a shunted S/2DEG/S junction.