Evaluation of the Bychkov- Rashba Field from the Spin Resonance of Electrons in a Si Quantum Well

From spin resonance of two-dimensional (2D) conduction electrons in a modulation doped SiGe/Si/SiGe quantum well structure we find a 2D anisotropy of both the line broadening (dephasing time) and the g-factor. We show that these can be explained consistently in terms of the Bychkov-Rashba (BR) field which here is the dominant coupling between electron motion and spin. We obtain a BR parameter of alpha = 1.1 e-12 eV cm - three orders of magnitude smaller as compared to III-V wells. Extrapolating for low electron concentrations we obtain a g-factor of the Si conduction band of 2.00073+/-0.00010.