Identification of the isolated arsenic antisite defect in electron-irradiated gallium arsenide and its relation to theEL2 defect

In semi-insulating GaAs, which was electron irradiated at 4.2 K and kept below 80 K, the isolated arsenic antiste ${\mathrm{As}}_{\mathrm{Ga}}$ defect could be identified with optically detected magnetic resonance (ODMR). It decays at about 300 K while an additional ${\mathrm{As}}_{\mathrm{Ga}}$ related defect is formed. Upon further heating to about 520 K this defect also decays and EL2 is formed. The magnetic circular dichroism of the absorption (MCDA) of the isolated ${\mathrm{As}}_{\mathrm{Ga}}$ defect has a simple derivativelike structure that is explained theoretically. Its MCDA and ODMR spectra are different from the corresponding EL2 spectra indicating the different microscopic structures of the defects. The isolated ${\mathrm{As}}_{\mathrm{Ga}}$ defect cannot be bleached into a metastable state at low temperature under the conditions where EL2 is bleached completely.