Anisotropic introduction of intrinsic defects in GaAs monitored by Raman scattering

We show that resonant Raman scattering can be used to monitor anisotropic introduction of intrinsic defects by electron irradiation. We do this by investigating a localized vibrational mode with a frequency of 227 ${\mathrm{cm}}^{\mathrm{-}1}$ that is associated with an intrinsic point defect and demonstrating that it is produced by displacement of the arsenic sublattice. Isochronal annealing measurements support this conclusion. The experimental results are consistent with the identification of this defect as either $V_{\mathrm{As}}$ or tetrahedrally located ${\mathrm{As}}_{\mathrm{i}}$.