Tunneling experiments into proximitized Ge/SiGe quantum well

Ge quantum wells in SiGe heterostructures are a promising platform for a new generation of quantum devices due to their high mobility [1], ability to be proximitized by superconductors and compatibility with standard Si CMOS fabrication technology among other advantages [2]. They have shown rapid progress as both spin qubits [3] and as superconducting devices [4]. In this presentation, I will report on the quality of the superconductor-semiconductor interface in Josephson junction field-effect transistors with the Ge as the weak link, quantifying the IcRn product, the excess current, and providing evidence of multiple Andreev reflection. Additionally, I will present recent experiments using a gate-defined QPC showing well-defined conductance plateaus and conductance enhancement when the DC bias is below the value of the superconducting gap. These gates are then used to define a tunnelling barrier to probe the proximitized density of states in the Ge from the superconductor similar to [5].



[1] Giordano Scappucci et al. Nature Reviews Materials, 1–26, 2020.

[2] Amir Sammak et al. Advanced Functional Materials, 29(14), 2019.

[3] Nico W. Hendrickx et al. Nature, 591(7851):580–585, 2021.

[4] Vigneau, F. et al. Nano Letters, 19(2), 1023–1027, 2019.

[5] Kjaergaard, et al. (2016). Nature Communications, 7.