Germanium wafers for strained quantum wells with low disorder
Lucas E. A. Stehouwer, Alberto Tosato, Davide Degli Esposti, Davide Costa, Menno Veldhorst, Amir Sammak, Giordano Scappucci
Abstract
We grow strained Ge/SiGe heterostructures by reduced-pressure chemical vapor deposition on 100 mm Ge wafers. The use of Ge wafers as substrates for epitaxy enables high-quality Ge-rich SiGe strain-relaxed buffers with a threading dislocation density of (6±1)×105 cm−2, nearly an order of magnitude improvement compared to control strain-relaxed buffers on Si wafers. The associated reduction in short-range scattering allows for a drastic improvement of the disorder properties of the two-dimensional hole gas, measured in several Ge/SiGe heterostructure field-effect transistors. We measure an average low percolation density of (1.22±0.03)×1010 cm−2 and an average maximum mobility of (3.4±0.1)×106 cm2/Vs and quantum mobility of (8.4±0.5)×104 cm2/Vs when the hole density in the quantum well is saturated to (1.65±0.02)×1011 cm−2. We anticipate immediate application of these heterostructures for next-generation, higher-performance Ge spin-qubits, and their integration into larger quantum processors.