Berlin 2008 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
HL: Fachverband Halbleiterphysik
HL 42: Optical Properties of Quantum dots: Theory and Simulation
HL 42.12: Talk
Thursday, February 28, 2008, 12:45–13:00, EW 201
Annealing of overgrown InAs/GaAs Quantum Dots:
A Tight-Binding Study — •Alexander Kleinsorge1, Thomas Hammerschmidt1, and Peter Kratzer2,1 — 1Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin, Germany — 2Fachbereich Physik, Universität Duisburg-Essen, D-47048 Duisburg, Germany
The electronic and optical properties of quantum dots (QDs) are determined by their atomic structure. A better understanding of this relationship requires input from electronic structure theory. We employ the empirical sp3s* tight-binding approach, including 2nd-nearest-neighbor interactions and spin-orbit coupling, preceded by structural relaxation using a potential of the Abell-Tersoff type. Large systems with up to 106 atoms can be treated using the folded-spectrum method.
To simulate the intermixing during annealing of InAs QDs in GaAs, we implemented a strain-driven kinetic Monte-Carlo (kMC) method, where the hopping rate of the cation vacancies depends on the differences of the relaxation energy (calculated with the Tersoff potential). Using strain-dependent rates in the kMC-Simulation leads to faster dissolving of the wetting layer. Because of the different shape of the electron and hole wavefunctions, the exciton is associated with a dipole moment which causes the experimentally observed Stark shift. We investigate how the dipole moment of the ground state exciton in a QD depends on the concentration profiles after annealing.