Si:Er:O layers grown by molecular beam epitaxy: structural, electrical and optical properties

The structural, electrical and optical properties of crystalline Si co-doped with Er and O by molecular beam epitaxy (MBE) and annealed at 900°C for 1 h have been investigated in detail. We observed clear constraints to the Er content that can be incorporated in a good quality single crystal. Moreover, we show that the O:Er ratio represents the main parameter in determining the properties of this system: Er electrical and optical activation increases with O:Er ratio until a saturation regime is achieved for a ratio higher than 6–8. We attribute this saturation regime to the full O coordinated first shell surrounding Er atoms in the Si host after the annealing at 900°C. In contrast, the most intense room temperature photoluminescence (PL) peak is obtained in samples having an O:Er ratio ∼2, for which PL temperature quenching is strongly reduced. Moreover, we investigated by X-ray photoelectron spectroscopy (XPS) the Er mobility for different temperatures and observed its penetration into the Si bulk from an Er/Si surface only after the annealing at 900°C. These phenomena are investigated in detail and discussed.