We show using deep-level transient spectroscopy (DLTS) that particle irradiation of GaAs : Si and GaAs : S introduces a defect Eα3 and a new defect EαIR10, respectively, and both these defects are metastable. We determine that Eα3 and EαIR10 are located 0.37 and 0.26 eV below the conduction band, respectively. Eα3 is removed by hole-injection and re-introduced during a first-order transformation under zero-bias annealing (at temperature T>160 K, and activation energy ∆E=0.40 eV), or during reverse-bias annealing (T>190 K and ∆E=0.53 eV). EαIR10 is removed by zero-bias annealing and re-introduced in the region 230-260 K, under predominantly first-order kinetics (activation energy ∆E=0.58 eV). Our results suggest that both defects Eα3 and EαIR10 are defect-impurity complexes that involve the Si and S dopants, respectively.