Defects with deep electronic energy levels induced by electron irradiation at room temperature or plastic deformation at 450°C in GaAs in which grown-in EL2 defects are previously eliminated by heat-treatment are investigated by means of measurements of the optical absorption and the Hall effect. Thermal stabilities of the induced defects are studied by tracing the changes mainly in the absorption specturm due to isochronal annealing. The absorptions both in deformed and irradiated specimens are mostly photo-unquenchable. Therefore, the defects induced by above two procedures are identified not to be EL2. Semi-insulating orn-type specimens convert top-type by plastic deformation or electron irradiation, showing that high densities of acceptors are generated by the above two procedures.