Electrical Properties of Selective-Area-Grown Superconductor-Semiconductor Hybrid Structures on Silicon

We present a superconductor-semiconductor materials system that is both scalable and monolithically integrated on a silicon substrate. It uses selective-area growth of $\mathrm{Al}$-$\mathrm{In}\mathrm{As}$ hybrid structures on a planar III-V buffer layer, grown directly on a high-resistivity silicon substrate. We characterize the electrical properties of this materials system at millikelvin temperatures and observe a high average field-effect mobility of $\ensuremath{\mu}\ensuremath{\approx}3200\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{2}\mathrm{/Vs}$ for the $\mathrm{In}\mathrm{As}$ channel and a hard induced superconducting gap. Josephson junctions exhibit a high interface transmission, $\mathcal{T}\ensuremath{\approx}0.75$, a gate-voltage-tunable switching current with a product of critical current and normal state resistance, ${I}_{C}{R}_{N}\ensuremath{\approx}83\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{V}$, and signatures of multiple Andreev reflections. These results pave the way for scalable and high-coherence gate-voltage-tunable transmon devices and other superconductor-semiconductor hybrids fabricated directly on silicon.