  We show that Ge concentration oscillations within the quantum well region of
a Si/SiGe heterostructure can significantly enhance the spin-orbit coupling of
the low-energy conduction-band valleys. Specifically, we find that for Ge
oscillation wavelengths near $\lambda = 1.57~\text{nm}$ with an average Ge
concentration of $\bar{n}_{\text{Ge}} = 5\%$ in the quantum well region, a
Dresselhaus spin-orbit coupling is induced, at all physically relevant electric
field strengths, which is over an order of magnitude larger than what is found
in conventional Si/SiGe heterostructures without Ge concentration oscillations.
This enhancement is caused by the Ge concentration oscillations producing
wave-function satellite peaks a distance $2 \pi/\lambda$ away in momentum space
from each valley, which then couple to the opposite valley through Dresselhaus
spin-orbit coupling. Our results indicate that the enhanced spin-orbit coupling
can enable fast spin manipulation within Si quantum dots using electric dipole
spin resonance in the absence of micromagnets. Indeed, our calculations yield a
Rabi frequency $\Omega_{\text{Rabi}}/B > 500~\text{MHz/T}$ near the optimal Ge
oscillation wavelength $\lambda = 1.57~\text{nm}$.
