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arXiv · 2305.08971

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
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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$\pm$1)$\times$10$^5$ 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$\pm$0.03)$\times$10$^{10}$ cm$^{-2}$, and an average maximum mobility of (3.4$\pm$0.1)$\times$10$^{6}$ cm$^2$/Vs and quantum mobility of (8.4$\pm$0.5)$\times$10$^{4}$ cm$^2$/Vs when the hole density in the quantum well is saturated to (1.65$\pm$0.02)$\times$10$^{11}$ cm$^{-2}$. We anticipate immediate application of these heterostructures for next-generation, higher-performance Ge spin-qubits and their integration into larger quantum processors.

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Lucas E. A. Stehouwer, Alberto Tosato, Davide Degli Esposti, Davide Costa, Menno Veldhorst, Amir Sammak, Giordano Scappucci. 2023-05-15. Germanium wafers for strained quantum wells with low disorder. https://doi.org/10.1063/5.0158262

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