TEM and PL characterization of erbium and oxygen co-implanted LT-GaAs:Be

Er and O have been co-implanted into Be doped low-temperature LT-GaAs. Plateau-like profiles from 10 to ∼145 nm below the sample surface and with an Er concentration at 1019 cm-3 were obtained. Samples with different Er to O ratios (1:0, 1:2, 1:4 and 1:8) were prepared and annealed in the 550-850 deg. C temperature range for 30 s. Photoluminescence (PL) data for samples with 1:2 ratio shows that Er intensity is enhanced by a factor of ∼5 as compared to the non-oxygen implanted samples. In order to optically activate Er higher temperatures are required compared to the samples where oxygen is not introduced. Once Er emission is activated, it is found to be thermally stable. Transmission electron microscopy (TEM) shows no Er-rich precipitation for the co-implanted samples while those samples without oxygen have ErAs precipitates. We believe that the absence of these precipitates in the co-implanted samples is responsible for better temperature stability for Er emission