We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities (2.0−11×1011 cm−2) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of Shubnikov-de Haas oscillations, we measure a light mass of 0.061me at a density of 2.2×1011 cm−2. We confirm the theoretically predicted dependence of increasing mass with density and by extrapolation we find an effective mass of ∼0.05me at zero density, the lightest effective mass for a planar platform that demonstrated spin qubits in quantum dots.
@article{arxiv.1905.08064,
title = {Light effective hole mass in undoped Ge/SiGe quantum wells},
author = {M. Lodari and A. Tosato and D. Sabbagh and M. A. Schubert and G. Capellini and A. Sammak and M. Veldhorst and G. Scappucci},
journal= {arXiv preprint arXiv:1905.08064},
year = {2019}
}