Wafer-scale CMOS-compatible graphene Josephson field-effect transistors

Abstract

Electrostatically tunable Josephson field-effect transistors (JoFETs) are one of the most desired building blocks of quantum electronics. JoFET applications range from parametric amplifiers and superconducting qubits to a variety of integrated superconducting circuits. Here, we report on graphene JoFET devices fabricated with wafer-scale complementary metal-oxide-semiconductor (CMOS) compatible processing based on wet transfer of chemical vapour deposited graphene, atomic-layer-deposited Al$_{2}$O$_{3}$ gate oxide, and evaporated superconducting Ti/Al source, drain, and gate contacts. By optimizing the contact resistance down to $\sim$ 170 $\Omega \mu m$, we observe proximity-induced superconductivity in the JoFET channels with different gate lengths of 150 - 350 nm. The Josephson junction devices show reproducible critical current $I_{\text{C}}$ tunablity with the local top gate. Our JoFETs are in short diffusive limit with the $I_{\text{C}}$ reaching up to $\sim\,$3 $\mu A$ for a 50 $\mu m$ channel width. Overall, our demonstration of CMOS-compatible 2D-material-based JoFET fabrication process is an important step toward graphene-based integrated quantum circuits.