Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 21: Quantum Dots and Wires, Optical Properties I: Nitrides

HL 21.5: Vortrag

Dienstag, 23. März 2010, 10:30–10:45, H17

Electronic and optical properties of nitride semiconductor quantum dots with wurtzite structure — •Stefan Barthel, Daniel Mourad, and Gerd Czycholl — Institut für Theoretische Physik, Universität Bremen, 28359 Bremen

A multiband empirical tight-binding model for group-III-nitride semiconductors with a wurtzite structure has been developed and applied to the calculation of the electronic and optical properties of (embedded) InN/GaN quantum dots. As a minimal basis set we assume one s-orbital and three p-orbitals localized in the unit cell of the hexagonal Bravais lattice, from which one (s-like) conduction band and three (p-like) valence bands are formed. Non-vanishing matrix elements up to second nearest neighbors are taken into account. These matrix elements are determined so that the resulting tight-binding band-structure reproduces the known Γ-point parameters. Furthermore, the tight-binding band-structure is also fitted to the band energies at other special symmetry (boundary) points of the Brillouin zone (known, in particular, from recent first-principles GW-calculations). These matrix elements allow for supercell calculations of the electronic properties of single and coupled quantum dots and for a separate wetting layer (quantum well) treatment. Crystal-field-splitting, spin-orbit coupling and the influence of intrinsic fields (spontaneous polarization, etc.) can be taken into account. The calculation of dipole and Coulomb matrix elements allows for the determination of excitonic spectra and selection rules within the configuration interaction (CI) scheme.