Carrier multiplication in quantum dots. Billiards packet ball mechanism, quantum fluctuations, and accompanying Raman scattering phenomena.
The carrier multiplication (CM) in spherical semiconductor quantum dots (QDs) as a re- sult of single photon absorption is studied. Semiconductors with simple parabolic electron- hole bands were considered when the band-to-band electron photon quantum transitions lead to creation of electron-hole...
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| Autores principales: | , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
D.Ghitu Institute of Electronic Engineering and Nanotechnologies
2008
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/50f249c1b8a147e88360981d8ce09663 |
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| Sumario: | The carrier multiplication (CM) in spherical semiconductor quantum dots (QDs) as a re-
sult of single photon absorption is studied. Semiconductors with simple parabolic electron-
hole bands were considered when the band-to-band electron photon quantum transitions lead
to creation of electron-hole (e-h) pairs with the same quantum numbers l, n, m of the envelope
functions for electron and hole. In the frame of the perturbation theory the electron-radiation
interband interaction with resonant and antiresonant terms as well as the electron-electron
Coulomb interaction representing the long-range dipole-dipole interaction was engaged.
A mechanism of the CM process similar with the packet balls in the billiards game is
proposed. An alternative mechanism related with the quantum fluctuation in the electron-
photon system leading to the simultaneous creation from the vacuum of one e-h pair and of a
secondary photon is discussed. When their creation energies are supplied by the energy of the
incident photon the CM process is accompanied by the Raman scattered photon. The creation
of two and three e-h pairs in both variants is described. In both cases the first matrix elements
between the initial state i and the first intermediary state 1 u are calculated on the base of
resonant interband electron-radiation interaction. In the billiards packet ball mechanism the
next matrix elements of the perturbation theory are calculated on the base of Coulomb interaction.
When the quantum fluctuations are taken into account one of the next matrix elements
is calculated on the base of the antiresonant part of the electron-radiation interaction.
In the first case the CM process is characterized by a lorentzian-type absorption peak,
whereas the CM accompanied by the Raman scattered photon is characterized by a smooth
absorption plateau. This difference can explain the existence of the threshold on the frequency
dependences of the CM quantum efficiency, in the spectral regions corresponding to creation
of two or three e-h pairs in different QDs. |
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