Identification of the arsenic vacancy defect in electron-irradiated GaAs

We report the systematic observation of a new electron-paramagnetic-resonance spectrum in a wide series of electron-irradiated GaAs crystals. The spectrum consists of a partially resolved multiplet of 700-G linewidth and an effective g factor of 2.00 for B∥[001] and 2.04 for B∥[110]. Comparison of its production behavior, photoexcitation spectrum, observability up to T=70 K and its thermal annealing at T=500 K with previous results obtained by capacitance spectroscopy, lead us to attribute it to the arsenic vacancy perturbed by a distribution of arsenic interstitials ($V_{\mathrm{As}{}^{\mathrm{-}}}$-${\mathrm{As}}_{\mathrm{i}}$). The experimental spectrum is well simulated in this model with the spin-Hamiltonian parameters S=1, $g_{?}$($V_{\mathrm{As}}$-${\mathrm{As}}_{\mathrm{i}}$)=2.00, $g_{\perp }$($V_{\mathrm{As}}$-${\mathrm{As}}_{\mathrm{i}}$)=2.02 and D=0.4 ${\mathrm{cm}}^{\mathrm{-}1}$.