In order to shed more light on the nature of EL2 defect in GaAs

this paper has investigated the EPR"AsGa" spactra in detail on the basis of EPR theory and quantum chemistry. The results show that the higher-order hyperfine interactions arisen from the multi -shell As and Ga nuclei around the AsGa antisite should be taken into account.Furthermore

combined with the annealing experimens of the neutron irradiated GaAs by Goltzene et al. in 1984

the effects of a vacancy （or vacancies） around the AsGa antisite on the linewidth and the hf constant of the EPR"AsGa"spectrum are discussed. In consequence

We suggest that the EPR"AsGa"might be caused not only by the isolated AsGa but also by some of its vacancy complexes.