Demonstration of two-dimensional hole gases (2DHG) in strained GeSn quantum wells*

In this work, capacitively induced two-dimensional hole gases in undoped Ge/GeSn heterostructures were demonstrated. Ge/GeSn heterostructures with Sn fractions of 6%, 9% and 11% were grown by chemical vapor deposition with surface roughness below 3 nm. Hall bar devices were fabricated and characterized at 4 K. Density saturation was observed and the highest mobility was 1.9x10⁴ cm²/Vs. The dominant scattering mechanism is likely background impurity scattering. Shubnikov-de Haas oscillations and the quantum Hall effect were observed at B > 1 T, indicating high-quality material growth of Ge/GeSn heterostructures. Effective masses were extracted by the temperature-dependent SdH oscillations.