Spin Lifetimes in annealed GaInNAs epilayers*

We have carried out Hanle measurements of the electron spin lifetime $T_{S} $in optically pumped annealed GaInNAs epilayers (undoped and p-type doped). The samples were placed in a 7T optical magnet cryostat with the magnetic field applied in the epilayer plane. The emitted light was collected along the normal to the epilayers. The PL was excited using the 1064 nm line from a Nd:YAG laser which gives a polarization P $=$ 5{\%} at B$=$0. The transverse magnetic field results in a reduction of $P$, from which we determine $T_{S}$. At $T=$50 K, the electron spin lifetime $T_{S} $was measured to be 15 ps. As the sample temperature increases, $T_{S} $decreases ($T_{S\thinspace }=$ 7 ps at T $=$ 150 K). Our Hanle results are in agreement with the $T_{S} $values measured by Lombez \textit{et al}. using time-resolved photoluminescence spectroscopy [2]. The observed sharp reduction in $T_{S} $in annealed samples is interpreted as due to the D'yakonov-Perel' spin relaxation mechanism. [3] In annealed samples the momentum relaxation time increases, resulting in a reduction of $T_{S}$ [2] L. Lombez et al, Appl Phys Lett 87, 252115(2005) [3] M.I. D'yakonov and V.I. Perel', Soviet Physics JETP, 33, 1053(1971)