Fabrication and characterization of two- and multi-terminal InAs/Al hybrid Josephson junctions (Part I)

We study superconductor (SC) /two-dimensional electron gas (2DEG) Josephson Junctions (JJ) based on InAs quantum well heterostructure with epitaxially grown Al. Recently, high-transparency interface between SC and 2DEG combined with high mobility and low density was demonstrated in this structure [1]. Thus, InAs/Al heterostructure is a promising platform for implementing topological superconductivity by proximity effect. A key step towards this task is understanding supercurrent and quasiparticle bound state spectrum of SC/2DEG/SC junctions. Here we present fabrication and characterization of conventional two-terminal and novel multi-terminal junctions. The latter devices are particularly interesting because theory predicts robust zero-energy bound states in a vanishing magnetic field due to the multi-arm interference of Andreev-reflected electrons and holes [2]. Ref: [1] J. Shabani, et. al., Phys. Rev. B 93, 155402 (2016); [2] B. van Heck, et al, Phys. Rev. B 90, 155450 (2014)