Spatial Imaging and Mechanical Control of Spin Coherence in Strained GaAs Epilayers

Recent work has shown that electron spins in GaAs and related compounds respond to strain dramatically. In particular, the manipulation of the spin-orbit coupling in GaAs via strain may be used for the development of all-electrical spintronic devices. Here we have developed a mechanical vise to controllably and reproducibly tune the tensile strain in-situ over a typical range for strain engineered heterostructures, from 0.0 - 0.2\%\footnote{H. Knotz, A Holleitner, J. Stephens, R. C. Myers, and D. D. Awschalom, submitted (2005)}. The effect of uniaxial tensile strain on spin coherence and transport phenomena in n-type GaAs epilayers is probed using time-resolved Kerr rotation, photoluminescence, and optically-detected nuclear magnetic resonance spectroscopies. The bandgap, electron spin lifetime, electron g-factor, and nuclear quadrupole splitting are imaged over millimeter scale areas of the epilayers for continuously varying values of strain. Simple non-destructive techniques for characterizing strain dependent phenomena in semiconductor heterostructures will facilitate the development of strain engineered spintronic devices.