  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.
