  Gate tunable junctions are key elements in quantum devices based on hybrid
semiconductor-superconductor materials. They serve multiple purposes ranging
from tunnel spectroscopy probes to voltage-controlled qubit operations in
gatemon and topological qubits. Common to all is that junction transparency
plays a critical role. In this study, we grow single crystalline InAs, InSb and
$\mathrm{InAs_{1-x}Sb_x}$ nanowires with epitaxial superconductors and in-situ
shadowed junctions in a single-step molecular beam epitaxy process. We
investigate correlations between fabrication parameters, junction morphologies,
and electronic transport properties of the junctions and show that the examined
in-situ shadowed junctions are of significantly higher quality than the etched
junctions. By varying the edge sharpness of the shadow junctions we show that
the sharpest edges yield the highest junction transparency for all three
examined semiconductors. Further, critical supercurrent measurements reveal an
extraordinarily high $I_\mathrm{C} R_\mathrm{N}$, close to the KO$-$2 limit.
This study demonstrates a promising engineering path towards reliable
gate-tunable superconducting qubits.
