Mapping Spin-Orbit Splitting in Strained (In,Ga)As Epilayers

Time-resolved and spatially resolved Faraday rotation spectroscopy is used to measure the magnitude and direction of the momentum-dependent spin splitting in strained InGaAs epilayers. The epilayers are lattice-matched to the GaAs substrate and designed to reduce inhomogeneous effects related to strain relaxation. Measurements of momentum-dependent spin splitting as a function of electron spin drift velocity along [100], [010], [110] and [1$\overline{1}$0] directions enable separation of isotropic and anisotropic effective magnetic fields that arise from uniaxial and biaxial strain along $\langle$110$\rangle$. Such electrically induced effective magnetic fields can be used for spin generation and manipulation in spintronics devices. We find that anisotropic and isotropic strain-induced effective magnetic fields are comparable in magnitude.~\footnote{B. M. Norman, C. J. Trowbridge, J. Stevens, A. C. Gossard, D. D. Awschalom, and V. Sih, Phys. Rev. B. {\bf 82}, 081304(R) (2010).}