Suppression of Donor-Driven Spin Relaxation in Strained Si0.1Ge0.9

Abstract

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 $n\text{\ensuremath{-}}\mathrm{type}\phantom{\rule{0.2em}{0ex}}{\mathrm{Si}}_{0.1}{\mathrm{Ge}}_{0.9}$ 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-${\mathrm{Si}}_{0.1}{\mathrm{Ge}}_{0.9}$ 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 ${\mathrm{Si}}_{0.1}{\mathrm{Ge}}_{0.9}$.