Reducing disorder in Ge quantum wells by using thick SiGe barriers

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)x10(6) cm(2)/Vs at a saturation density of (1.72 +/- 0.03)x10(11) cm(-2), corresponding to a long mean free path of (30 +/- 1)mu m. The highest measured mobility is 4.68x106 cm(2)/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)x10(9) cm(-2). This low-disorder heterostructure, according to simulations, may support the electrostatic confinement of holes in gate-defined quantum dots. C2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/).https://doi.org/10.1063/5.0242746