Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 19: Quantum dots and wires: Optical properties II

HL 19.1: Vortrag

Dienstag, 28. März 2006, 17:15–17:30, HSZ 01

Influence of doping on the electronic and optical properties of Si nanocrystallites — •Luis Ramos¹, Elena Degoli², Stefano Ossicini², Jürgen Furthmüller¹, and Friedhelm Bechstedt¹ — ¹Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena, Germany — ²Università di Modena e Reggio Emilia, via Fogliani, I-42100 Reggio Emilia, Italy

Silicon nanocrystallites (NCs) have been intensively studied in the last years, since they can confine holes and electrons and circumvent the indirect-gap character of the lowest-energy optical transitions of Si bulk. Besides quantum confinement, oxidation, oxygen-related defects,[1] and doping have been investigated. Recently, an increase of the photo luminescence (PL) intensity was observed for Si NCs doped with both group-III and group-V species. Since measurements for single NCs are difficult, ab initio theoretical investigations become important to suggest dopants and to clarify the mechanisms of PL in Si NCs. Our calculations are based on the density-functional theory, the generalized-gradient approximation, the projector-augmented wave method, and the pseudopotential approximation. The electronic structure and optical absorption spectra of free-standing doped Si NCs of different sizes and shapes are investigated in simple-cubic supercells. Besides the influence of shape and size on the impurity formation energies, bond lengths, and radiative lifetimes, significant changes in the optical absorption spectra are predicted for Si NCs doped with group-V impurities.

[1] L.E. Ramos, J. Furthmüller, and F. Bechstedt, Appl. Phys. Lett. 87, 143113 (2005); Phys. Rev. B 71, 035328 (2005)