Supercurrent–phase relation of a Nb/InAs(2DEG)/Nb Josephson junction

Using an RF-SQUID configuration we have measured the temperature dependence of the current–phase relation (CPR) of Nb/InAs(2DEG)/Nb (two-dimensional electron gas, 2DEG) Josephson junctions with high interface transparency. At low temperatures, significant deviations from a sinusoidal CPR are observed. The experimental results are fitted by the scattering matrix theory of Brouwer and Beenakker, additionally taking into account the proximity effect between the Nb and the 2DEG in the inversion layer on p-type bulk InAs. We have studied also the influence of an external gate voltage applied to the InAs(2DEG) channel. It is shown that the amplitude of RF-SQUID oscillations can be controlled by gate voltage with only modest deterioration of the SQUID signal.