Electron-paramagnetic-resonance observation of gallium vacancy in electron-irradiatedp-type GaAs

We report an observation by electron paramagnetic resonance (EPR) of the gallium vacancy defect in GaAs. The defect is observed after electron irradiation of p-type GaAs. The gallium vacancy defect shows trigonal symmetry; its spin-Hamiltonian parameters are determined as S=1/2, ${\mathit{g}}_{\mathrm{\parallel }\left[111\right]}$=1.98±0.02, ${\mathit{g}}_{\mathrm{\perp }\left[111\right]}$=2.08±0.01, ${\mathit{A}}_{\mathrm{\parallel }\left[111\right]}$=(280±20)×${10}^{\mathrm{-}4}$ ${\mathrm{cm}}^{\mathrm{-}1}$, and ${\mathit{A}}_{\mathrm{\perp }\left[111\right]}$=(130±10)×${10}^{\mathrm{-}4}$ ${\mathrm{cm}}^{\mathrm{-}1}$. A tight-binding Green’s function calculation confirms the defect model and identifies its charge state as 2-. The gallium vacancy is unstable at room temperature, the thermal annealing parameters being Fermi-level dependent.