Magnetotransport Characterization of P-Type, Gated Ge Quantum Wells Grown by Molecular Beam Epitaxy with Epitaxial Al Contacts

Two-dimensional hole gases in undoped germanium quantum wells combined with highly transparent epitaxial aluminum contacts provide a promising platform for a variety of gate-controlled quantum devices. Such devices would benefit from the high mobility and low effective mass of holes in Ge while avoiding scattering from dopants or interfaces. This talk will discuss the electrical characterization of undoped Ge quantum wells in SiGe heterostructures grown by molecular beam epitaxy. An electrostatic gate induces a two-dimensional hole gase in which we observed quantum Hall effect and carrier mobility > 5x10⁴ cm²/Vs in the density range 0.5-1 x 10¹²cm^-2. Weak dependence of the mobility on density suggests that mobility is limited by scattering from impurities within the quantum well. Looking ahead to micron-scale quantum devices based on this material, we also investigate the impact of edge effects due to proximity to the mesa edge.