Characterization of Voltage-Tunable Ge/SiGe Josephson Junctions for Gatemon Qubits

Combining the transparent interface of epitaxial aluminum (Al) contacts with the two-dimensional hole gas in an undoped germanium (Ge) quantum well provides a promising platform for gate-tunable quantum devices. Superconductor-semiconductor hybrid Josephson junctions made from these materials require high mobility and low scattering from dopants or interfaces. Here, we report the electrical characterization of voltage-tunable Al-Ge-Al hybrid Josephson junctions in which the undoped and strained Ge quantum wells that reside in silicon germanium (SiGe) heterostructures grown by molecular beam epitaxy. This presentation will discuss the observed proximity induced superconductivity in Ge/SiGe Josephson junction devices for a variety of junction lengths and widths to inform the design of voltage-tunable SiGe qubits.