Suppression of Donor-Driven Spin Relaxation in Strained Si 0.1 Ge 0.9

We experimentally study the strain effect on electron spin relaxation in a semiconductor using nonlocal spin-transport measurements in lateral spin-valve devices. Application of in-plane and biaxial tensile strain to a (111)-oriented and heavily doped n-type Si0.1Ge0.9 layer leads to lifting of the valley degeneracy in the conduction band and to reduction of the electron's effective mass, resulting in increased electron mobility. Nonlocal four-terminal spin signals in the strained-Si0.1Ge0.9 lateral spin-valve devices are markedly enhanced and the estimated spin lifetime becomes 3 times longer than that in strain-free devices at low temperatures. On the basis of a comparison of the experimental data and recent theories, we propose that only the donor-driven intervalley spin-flip scattering of electrons at low temperatures is partly suppressed for the strained and heavily doped Si0.1Ge0.9.