Reducing disorder in Ge quantum wells by using thick SiGe barriers
Davide Costa (TU Delft - QCD/Scappucci Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Lucas E.A. Stehouwer (Kavli institute of nanoscience Delft, TU Delft - QCD/Scappucci Lab, TU Delft - QuTech Advanced Research Centre)
Yi Huang (University of Maryland)
Sara Martí-Sánchez (BIST)
Davide Degli Esposti (TU Delft - QCD/Scappucci Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Jordi Arbiol (BIST, Catalan Institution for Research and Advanced Studies (ICREA))
Giordano Scappucci (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, TU Delft - QCD/Scappucci Lab)
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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 ) × 10 6 cm 2 / Vs at a saturation density of ( 1.72 ± 0.03 ) × 10 11 cm − 2 , corresponding to a long mean free path of ( 30 ± 1 ) μ m . The highest measured mobility is 4.68 × 10 6 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 ) × 10 9 cm − 2 . This low-disorder heterostructure, according to simulations, may support the electrostatic confinement of holes in gate-defined quantum dots.
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