Browsing by Author "Ramirez, H. Y."

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Analytical calculation of eigen-energies for lens-shaped quantum dot with finite barriers
(2008-11-01)
Rodriguez, A. H.
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Ramirez, H. Y.
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電子物理學系
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Department of Electrophysics
The bound states of a particle in a lens-shaped quantum dot with finite confinement potential are obtained in the envelope function approximation. The quantum dot has circular base with radius a and maximum cap height b, and the effective mass of the particle is considered different inside and outside the dot. A 2D Fourier expansion is used in a semi-sphere domain with infinite walls which contains the geometry of the original potential. Electron energies for different values of lens deformation b/a, lens radius a and barrier height V(o) are calculated. In the very high confinement potential limit, the results for the infinite barrier case are recovered.
Optical fine structures of highly quantized InGaAs/GaAs self-assembled quantum dots
(2010-06-30)
Ramirez, H. Y.
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Lin, C. H.
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Chao, C. C.
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Hsu, Y.
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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.