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 degreesC for 1 h have been investigated in detail. We observed clear constraints to the Ef 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 degreesC. In contrast, the most intense room temperature photoluminescence (PL) peak is obtained in samples having an O:Er ratio similar to 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 degreesC. These phenomena are investigated in detail and discussed. (C) 2001 Elsevier Science B.V. All rights reserved. RI Mirabella, Salvo/E-4672-2010