Symmetry determination of the EL2 defect by numerical fitting of capacitance transients under uniaxial stress

The symmetry of the EL2 center in n-type liquid-encapsulated Czochralski GaAs is investigated through numerical fitting of capacitance transients measured under uniaxial stress. From experimental data which superficially appears compatible with Td symmetry, we extract reproducible defect energy-level splitting under uniaxial stress and conclude that EL2 has C3v symmetry, supporting the AsGa-Asi pair model with Asi weakly bound to AsGa.