Abstract
We investigate the disorder properties of two-dimensional hole gases in Ge/SiGe heterostructures grown on Ge wafers, using thick SiGe barriers to mitigate the influence of the semiconductor-dielectric interface. Across several heterostructure field effect transistors we measure an average maximum mobility of (4.4 ± 0.2) × 10⁶ cm²/Vs at a saturation density of (1.72 ± 0.03) × 10¹¹ cm⁻², corresponding to a long mean free path of (30 ± 1) μ m. The highest measured mobility is 4.68 × 10⁶ cm²/Vs. We identify uniform background impurities and interface roughness as the dominant scattering mechanisms limiting mobility in a representative device, and we evaluate a percolation-induced critical density of (4.5 ± 0.1)× 10⁹ cm⁻². This low-disorder heterostructure, according to simulations, may support the electrostatic confinement of holes in gate-defined quantum dots.