Thermal annealing effects on the optical properties of erbium (Er)-ion-implanted AlxGa1-xAs layers grown on GaAs by metalorganic chemical vapor deposition were investigated by photoluminescence (PL), photoreflectance (PR), and Raman scattering measurements, The results of the Hall effect measurements showed that the carrier concentration of the Er+-implanted n-type AlxGa1-xAs layer decreases as the magnitude of the Er dose decreases. The results of the PL spectra for the as-grown AlxGa1-xAs layers showed two peaks related to the bound exciton (B, X) and to the recombination between the carbon acceptor impurities and the electrons in the conduction band (e, A degrees)(c). As the magnitude of the Er-ion dose increased, the (e, A degrees)(c) and (B, X) peaks shifted to their higher energy sides. The results of the PR spectra showed that the broadening parameter decreased as the Er dose increased. This behavior originates from the passivation of the mobile carriers, The results of the Raman scattering measurements for the as-grown AlxGa1-xAs layers showed that a peak appeared at 290 cm(-1) corresponding to the GaAs-like longitudinal optical (LO) phonon. When the Er-ion implantation in AlxGa1-xAs was accomplished at 1 MeV with a dose of 5 X 10(13) cm(-2) the GaAs LO phonon peak disappeared. After thermal treatment, the results of the PL and PR spectra indicate that the number of donors decreases due to the formation of the donor-acceptor pairs. Those of the FL, PR and the Raman spectra show that the damaged crystallinity of the Er-doped AlxGa1-xAs layers is improved by thermal treatment. This result indicates that mobile carriers in the AlxGa1-xAs layers an passivated by the Er-ion injection and that the passivated AlxGa1-xAs layers are recovered by thermal treatment.