ODMR investigation of proton irradiated GaAs

We have investigated, using electron paramagnetic resonance(EPR) detected via the magnetic circular dichroism of the optical absorption (MCDA) the defects introduced in bulk Te-doped and semi-insulating(SI) GaAs during 2.3 and 6.0 MeV proton irradiation at 300 K. We conclude that high energy proton irradiation of Te-GaAs introduced the anti-structure pair (AS(Ga) -Ga-As (nnn)) and As-Ga -V-As This is similar to the situation in the same material irradiated with high-energy electrons. Contrary to what is observed in electron irradiated SI-GaAs, the EL2 (EL2(0) and EL2(+)) defect is introduced during proton irradiation at 300 K, the total introduction rate being of the order of 50 +/- 25 cm(-1). Annealing to 600 K did not influence the concentration of EL2. Apart from the As-Ga - Ga-As (nnn) and the EL2 defects, a new defect was detected after proton irradiation of SI-GaAs. This isotropic defect which has a Gaussian EPR line shape, g = 2.02 and a FWHM of 90 mT is believed to be an acceptor like defect.