Effects of thermal annealing on the optical properties of Er-ion-implanted Al xGa 1− xAs layers grown on GaAs substrates

Abstract

Thermal annealing effects on the optical properties of erbium (Er)-ion-implanted Al x Ga 1− x As 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 Al x Ga 1− x As layer decreases as the magnitude of the Er dose decreases. The results of the PL spectra for the as-grown Al x Ga 1− x As 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°) c. As the magnitude of the Er-ion dose increased, the (e, A°) 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 Al x Ga 1− x As 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 Al x Ga 1− x As was accomplished at 1 MeV with a dose of 5×10 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 PL, PR and the Raman spectra show that the damaged crystallinity of the Er-doped Al x Ga 1− x As layers is improved by thermal treatment. This result indicates that mobile carriers in the Al x Ga 1− x As layers are passivated by the Er-ion injection and that the passivated Al x Ga 1− x As layers are recovered by thermal treatment.