Proximity Effect Transfer from NbTi into a Semiconductor Heterostructure   via Epitaxial Aluminum
  We demonstrate the transfer of the superconducting properties of NbTi---a large-gap high-critical-field superconductor---into an InAs heterostructure via a thin intermediate layer of epitaxial Al. Two device geometries, a Josephson junction and a gate-defined quantum point contact, are used to characterize interface transparency and the two-step proximity effect. In the Josephson junction, multiple Andreev reflection reveal near-unity transparency, with an induced gap $\Delta^*=0.50~\mathrm{meV}$ and a critical temperature of $7.8~\mathrm{K}$. Tunneling spectroscopy yields a hard induced gap in the InAs adjacent to the superconductor of $\Delta^*=0.43~\mathrm{meV}$ with substructure characteristic of both Al and NbTi. 
A. C. C. Drachmann, H. J. Suominen, M. Kjaergaard, B. Shojaei, C. J.   Palmstr{\o}m, C. M. Marcus, F. Nichele
cond-mat.mes-hall cond-mat.supr-con