First Demonstration of Superconducting Nb Contact on Heavily-Doped Group IV Semiconductor

We report the first demonstration of superconducting Nb contact on highly boron-doped
$\text{Si}_{035}\text{Ge}_{06}$
, achieving an ultra-low contact resistivity
$(p_{c})$
of
$5.22\times 10^{10}\Omega-\text{cm}^{2}$
at 295 K on
$\text{Si}_{035}\text{Ge}_{065}$
with active doping concentration
$(N_{A})$
of
$2.80\times 10^{21}$
cm’. We discover that the contact resistance
$(R_{c})$
remains low from 295 K to 6 K, with only slight increase from
$1.80\times 10^{4}$
to
$2.47\times 10^{4} \Omega\text{-cm}$
. However, the superconducting nature of the Nb film at 6 K enables the realization of 28% reduction in total resistance compared with the
$\text{Ti}/\text{Si}_{035}$
Ge0.65 contact. Such property can be obtained with a process thermal budget up to
$18 0^{0}\mathrm{C}$
, demonstrating its quantum compatibility.