Spin Lifetime Measurements of GaAsBi Films

Substituting a small amount of As with Bi, the largest non-radioactive group V element, leads to a large reduction in the GaAs band gap and expected large spin-orbit effects \footnote{B. Fluegel et al., \textbf{Giant Spin-Orbit Bowing in GaAs$_{1-x}$Bi$_{x}$}, Phys. Rev. Lett. \textbf{97}, 067205 (2006).}. Both properties are advantageous with potential applications ranging from infrared detectors to spin valves. Compressively strained GaAsBi films with varying bismuth compositions were grown on GaAs using molecular-beam epitaxy. Spin lifetimes were measured using the Hanle effect, a magneto-optical technique where an out-of-plane spin polarization is generated by circularly polarized light and then made to precess about an in-plane magnetic field. A Lorentzian lineshape can be fit to the field-dependent photoluminescence polarization to extract $gT_s$, where $g$ is the Lande g-factor and $T_s$ is a function of the carrier recombination time and spin dephasing time and provides a lower bound for both. Temperature and power dependent measurements were conducted and our extracted values for $gT_s$ vary from 100ps to 1ns.