Quantum Transport and Scattering Time Engineering in Nanostructures
Final rept. 1 Apr 1999-30 Nov 2002
ILLINOIS UNIV AT URBANA COORDINATED SCIENCE LAB
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We studied theoretically the electronic properties of single and vertically coupled InAsGaAs self-assembled quantum dots SAD with a computational model which takes into account conduction-valence band mixing through an eight-band strain dependent k.p hamiltonian. In single SADs, we showed that experimental photoluminescence peaks cannot be simply interpreted as transitions between harmonic oscillator states in the valence band and in the conduction band. We also provided a detailed account of electron-hole alignment as a function of external electric fields SAD chemical composition Ga diffusion profile in the dot and the dot shape. In particular, we invalidated the perturbation theory in the interpretation of the interband Stark effect. In vertically stacked coupled SADs we specifically demonstrated the localization of hole states, even for vanishing dot separation. We also predicted the existence of an anomalous Stark effect for interband transitions. We also showed that intraband optical transitions between 1s and 2p bonding states in the conduction band, are strongly enhanced compared with similar transitions in single SADs. These transitions exhibit a strong asymmetric dependence in an external electric field, due to the SAD morphology. The intraband Stark effect also provides large tunability between electron states for mid-infrared transitions.
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