| 1. |
- Donchev, V., et al.
(författare)
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Enhancement of the photoluminescence intensity of a single InAs/GaAs quantum dot by separate generation of electrons and holes
- 2006
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Ingår i: Physics of the solid state. - 1063-7834 .- 1090-6460. ; 48:10, s. 1993-1999
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Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that the microphotoluminescence (µPL) spectrum of a single InAs/GaAs self-assembled quantum dot (QD) undergoes considerable changes when the primary laser excitation is complemented with an additional infrared laser. The primary laser, tuned slightly below the GaAs band gap, provides electron-hole pairs in the wetting layer (WL), as well as excess free electrons from ionized shallow acceptors in the GaAs barriers. An additional IR laser with a fixed energy well below the QD ground state transition generates excess free holes from deep levels in GaAs. The excess electron and hole will experience diffusion separately, due to the time separation between the two events of their generation, to eventually become captured into the QD. Although the generation rates of excess carries are much lower than that of the electron-hole pair generation in the WL, they considerably influence the QD emission at low temperatures. The integrated PL intensity increases by several times as compared to single-laser excitation, and the QD exciton spectrum is redistributed in favor of a more neutral charge configuration. The dependence of the observed phenomenon on the powers of the two lasers and the temperature has been studied and is consistent with the model proposed. The concept of dual excitation could be successfully applied to different low-dimensional semiconductor structures in order to manipulate their charge state and emission intensity. © Nauka/Interperiodica 2006.
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| 2. |
- Holtz, Per-Olof, 1951-, et al.
(författare)
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Effects of External Fields on the Excitonic Emission from Single InAs/GaAs Quantum Dots
- 2008
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Ingår i: Microelectronics Journal, Vol. 39. - Microelectronics Journal : Elsevier. ; , s. 331-334
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Konferensbidrag (refereegranskat)abstract
- A low-temperature micro-photoluminescence (μ-PL) investigation of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field is reported. It is demonstrated that the QDs PL signal could be increased several times by altering the external and/or the internal electric field. The internal field in the vicinity of the dots could be altered by means of an additional infra-red laser. We propose a model, which is based on an essentially faster lateral transport of the charge carriers achieved in an external electric field. Consequently, also the capture probability into the dots and subsequently the dot luminescence is also enhanced. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment.
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| 8. |
- Larsson, Arvid, 1979-, et al.
(författare)
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Charge state control of single InAs/GaAs quantum dots by means of an external magnetic field
- 2008
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Ingår i: in PHYSICS OF SEMICONDUCTORS, vol 1199. - : AIP. - 9780735407367 ; , s. 297-298
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Konferensbidrag (refereegranskat)abstract
- Individual InAs/GaAs quantum dots (QDs) are studied with micro-photoluminescence in the presence of an applied external magnetic field. Attention is focused on the redistribution between the spectral lines of a single QD observed at increased external magnetic field when the magnetic field is applied parallel to the growth direction (Faraday geometry). The effect is shown to be transport related as the electron drift velocity in the QD-plane is decreased by the applied magnetic field and this affects the probability for electron capture into the QD.
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| 9. |
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| 10. |
- Larsson, Mats, et al.
(författare)
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Magnetic field effects on optical and transport properties in InAs/GaAs quantum dots
- 2006
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Ingår i: Physical Review B. - 1098-0121. ; 74:24
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Tidskriftsartikel (refereegranskat)abstract
- A photoluminescence study of self-assembled InAs/GaAs quantum dots under the influence of magnetic fields perpendicular and parallel to the dot layer is presented. At low temperatures, the magnetic field perpendicular to the dot layer alters the in-plane transport properties due to localization of carriers in wetting layer (WL) potential fluctuations. Decreased transport in the WL results in a reduced capture into the quantum dots and consequently a weakened dot-related emission. The effect of the magnetic field exhibits a considerable dot density dependence, which confirms the correlation to the in-plane transport properties. An interesting effect is observed at temperatures above approximately 100 K, for which magnetic fields, both perpendicular and parallel to the dot layer, induced an increment of the quantum dot photoluminescence. This effect is ascribed to the magnetic confinement of the exciton wave function, which increases the probability for carrier capture and localization in the dot, but affects also the radiative recombination with a reduced radiative lifetime in the dots under magnetic compression.
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| 11. |
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| 14. |
- Moskalenko, Evgenii, et al.
(författare)
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Carrier transport in self-organized InAs/GaAs quantum-dot structures studied by single-dot spectroscopy
- 2006
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Ingår i: Physical Review B. - 1098-0121. ; 73:15
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Tidskriftsartikel (refereegranskat)abstract
- A microphotoluminescence study of single InAs/GaAs quantum dots subjected to a lateral external electric field gives insight into carrier transport and capture processes into Stranski-Krastanov-grown quantum dots. The results obtained on the excitons in a single dot demonstrate a considerable luminescence intensity enhancement of the dot as well as a charge redistribution when an electric field is applied. The charge reconfiguration is evidenced by the transition from a predominantly negatively charged to a neutral charge state of the exciton. The model proposed to explain the charge redistribution is based on an effective hole localization at the potential fluctuations of the wetting layer.
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| 15. |
- Moskalenko, Evgenii, et al.
(författare)
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Comparative Magneto-Photoluminescence Study of Ensembles and of Individual InAs Quantum Dots
- 2009
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 9:1, s. 353-359
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Tidskriftsartikel (refereegranskat)abstract
- We report on magneto-photoluminescence studies of InAs/GaAs quantum dots (QDs) of considerably different densities, from dense ensembles down to individual dots. It is found that a magnetic field applied in Faraday geometry decreases the photoluminescence (PL) intensity of OD ensembles, which is not accompanied by the corresponding increase of PL signal of the wetting layer on which ON are grown. The model suggested to explain these data assumes considerably different strengths of suppression of electron and hole fluxes by a magnetic field. This idea has been successfully checked in experiments on individual ON, where the PL spectra allow to directly monitor the charge state of a OD and, hence, to conclude about relative magnitudes of electron and hole fluxes toward the QD. Comparative studies of different individual QDs have revealed that the internal electric field in the sample (which was altered in the experiments in a controllable way) together with an external magnetic field will determine the charge state and emission intensity of the QDs.
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| 16. |
- Moskalenko, Evgenii, et al.
(författare)
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Effect of an electric field on the carrier collection efficiency of InAs quantum dots
- 2005
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Ingår i: Physics of the solid state. - : Pleiades Publishing Ltd. - 1063-7834 .- 1090-6460. ; 47:11, s. 2154-2161
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Tidskriftsartikel (refereegranskat)abstract
- Individual and multiquantum dots of InAs are studied by means of microphotoluminescence in the case where, in addition to the principal laser exciting photoluminescence, second infrared laser is used. It is demonstrated that the absorption of the infrared photons effectively creates free holes in the sample, which leads to both a change in the charge state of a quantum dot and to a considerable reduction of their photoluminescence signal. The latter effect is explained in terms of effective screening of the internal electric field, facilitating carrier transport along the plane of a wetting layer, by the surplus holes from the infrared laser. It is shown that the effect of quenching of quantum dot photoluminescence gradually disappears at increased sample temperature (T) and/or dot density. This fact is due to the essentially increased value of quantum dot collection efficiency, which could be achieved at elevated sample temperatures for individual quantum dots or even at low T for the case of multiquantum dots. It is suggested that the observed phenomena can be widely used in practice to effectively manipulate the collection efficiency and the charge state of quantum-dot-based optical devices. © 2005 Pleiades Publishing, Inc.
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| 17. |
- Moskalenko, Evgenii, et al.
(författare)
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Effective tuning of the charge state of a single InAs/GaAs quantum dot by an external magnetic field
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:7, s. 075306-
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Tidskriftsartikel (refereegranskat)abstract
- A microphotoluminescence study of single InAs/GaAs quantum dots (QDs) in the presence of an applied external magnetic field is presented. Attention is focused on the redistribution between the spectral lines of a single QD observed at increasing magnetic field parallel to the growth direction (Faraday geometry). The redistribution effect is explained by considering the electron drift velocity in the QD plane that affects the probability for capture into the QD. In contrast, no redistribution is observed when applying the magnetic field perpendicular to the growth direction (Voigt geometry).
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| 18. |
- Moskalenko, Evgenii, et al.
(författare)
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Effects of separate carrier generation on the emission properties of InAs/GaAs quantum dots
- 2005
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 5:11, s. 2117-2122
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Tidskriftsartikel (refereegranskat)abstract
- Individual quantum dots have been studied by means of microphotoluminescence with dual-laser excitation. The additional infrared laser influences the dot charge configuration and increases the dot luminescence intensity. This is explained in terms of separate generation of excess electrons and holes into the dot from the two lasers. With increasing dot density and/or sample temperature, the increase of the luminescence intensity vanishes progressively, while the possibility to control the dot charge remains. © 2005 American Chemical Society.
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| 19. |
- Moskalenko, Evgenii, 2000-, et al.
(författare)
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Enhancement of the luminescence intensity of InAs/GaAs quantum dots induced by an external electric field
- 2007
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 7:1, s. 188-193
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Tidskriftsartikel (refereegranskat)abstract
- InAs/GaAs quantum dots have been subjected to a lateral external electric field in low-temperature microphotoluminescence measurements. It is demonstrated that the dot PL signal could be increased several times depending on the magnitude of the external field and the strength of the internal (built-in) electric field, which could be altered by an additional infrared illumination of the sample. The observed effects are explained by a model that accounts for the essentially faster lateral transport of the photoexcited carriers achieved in an electric field. © 2007 American Chemical Society.
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| 20. |
- Moskalenko, Evgenii, et al.
(författare)
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Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 80:19, s. 193413-
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Tidskriftsartikel (refereegranskat)abstract
- A high degree of spin polarization for the neutral exciton in individual quantum dots, at zero external magnetic field, is monitored. While a high polarization degree is commonly observed for the charged exciton, a negligible polarization has been predicted for the neutral exciton. The exceptionally high polarization (andgt;60%) observed here is explained in terms of a dynamical nuclear polarization field, stabilizing the electron spin. Such polarization of the quantum dot nuclei, in case of the neutral exciton, is possible due to unequal capture time of electrons and holes.
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| 21. |
- Moskalenko, Evgenii, 2000-, et al.
(författare)
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The effect of the external lateral electric field on the luminescence intensity of InAs/GaAs quantum dots
- 2007
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Ingår i: Physics of the solid state. - 1063-7834 .- 1090-6460. ; 49:10, s. 1995-1998
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Tidskriftsartikel (refereegranskat)abstract
- We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications.
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| 22. |
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