Magnetic circular dichroism of the diamagnetic charge state of EL2 in GaAs

Within the magnetic circular dichroism spectrum of the optical absorption of semi‐insulating GaAs, a temperature‐independent line was observed for the first time. This line is located at 1.19 eV and we ascribe it to the same transition which causes the optical absorption line of diamagnetic EL20. We consider first implications for the electronic structure of EL2 and use this line for the analysis of the charge state of EL2 in e−‐irradiated GaAs. It is shown that by annealing of low‐temperature e−‐irradiated GaAs, the concentration of EL2 defects can be made at least an order of magnitude higher than after thermal treatment.