Dresden 2006 – scientific programme
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HL: Halbleiterphysik
HL 40: Quantum dots and wires: Optical properties III
HL 40.5: Talk
Thursday, March 30, 2006, 12:00–12:15, POT 151
Effect of Size and Shape on the Single-Particle Spectrum of InAs/GaAs Quantum Dots: A Tight-Binding Study — •Alexander Kleinsorge1, Peter Kratzer1, Matthias Scheffler1, Roberto Santoprete2, and Belita Koiller2 — 1Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin, Germany — 2Instituto de Fisica, Universidade Federal do Rio de Janeiro, Brazil
With the help of electronic structure calculations, the electronic and optical properties of quantum dots (QDs) can be related to their atomic structure. We employ the empirical sp3s* tight-binding approach, including second-nearest neighbor interactions and spin-orbit coupling, preceded by structural relaxation using a potential of the Abell-Tersoff type to obtain the atomic positions. The folded-spectrum method to calculate selected eigenstates of the Hamiltonian allows us to treat large systems (up to 106 atoms). We apply our method to buried InAs quantum dots in GaAs, comparing pyramidal shapes with {101} or {111} side facets with more realistic truncated pyramids, hut-like, or dome-like shapes. The total number of electron and hole bound states, their energy and spatial extent are determined as a function of the QD size and shape. In particular, we find that energy splitting between p-like electron states is due to the symmetry properties of the zincblende lattice, rather than the symmetry of the QD shape. Piezoelectric effects arising from shear strain (treated as an external potential) are included, but found to be small (≈ 5 meV) for the QD sizes considered. Moreover, we compare the wavefunctions in free standing dots to experimental STM images.