Browsing by Author "Chao, C. C."

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Optical fine structures of highly quantized InGaAs/GaAs self-assembled quantum dots
(2010-06-30)
Ramirez, H. Y.
;
Lin, C. H.
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Chao, C. C.
;
Hsu, Y.
;
You, W. T.
A theoretical model for the electron-hole exchange interaction in three-dimensionally (3D) confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings (FSSs) of small InGaAs/GaAs self-assembled quantum dots (QDs) with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged e-h exchange interaction and leads to the reduced FSSs in the regime of high emission energy.
Singlet-triplet transitions in highly correlated nanowire quantum dots
(2010-02-01)
Chen, Y. T.
;
Chao, C. C.
;
Huang, S. Y.
;
Tang, C. S.
;
Cheng, S. J.
We consider a quantum dot embedded in a three-dimensional nanowire with tunable aspect ratio a. A configuration interaction theory is developed to calculate the energy spectra of the finite ID quantum dot systems charged with two electrons in the presence of magnetic fields B along the wire axis. Fruitful singlet-triplet transition behaviors are revealed and explained in terms of the competing exchange interaction, correlation interaction, and spin-Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions are shown designable by tuning the parameters a and B. The transition also manifest the highly correlated nature of long nanowire quantum dots. (C) 2009 Elsevier B.V. All rights reserved.