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| 2. |
- Karlsson, Fredrik, 1974-, et al.
(författare)
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Effective tuning of the charge-state of single In(Ga)As/GaAs quantum dots by below barrier band gap excitation
- 2003
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 532-535, s. 843-847
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Tidskriftsartikel (refereegranskat)abstract
- The existence of a well-defined threshold energy, crucial for the charging of quantum dots (QDs), positioned between the barrier band gap and the wetting layer ground state is demonstrated. Optical excitation with energies above this threshold populates the QDs with extra electrons. The origin of the threshold is discussed in terms of acceptors in the GaAs barrier. ⌐ 2003 Elsevier Science B.V. All rights reserved.
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| 3. |
- Karlsson, Fredrik, 1974-, et al.
(författare)
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Optical charging of self-assembled InAs/GaAs quantum dots
- 2002
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Ingår i: Physica scripta. T. - 0281-1847. ; 101, s. 140-142
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Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that the photoluminescence spectra of single self-assembled quantum dots are very sensitive to the experimental conditions, such as excitation energy and crystal temperature. A qualitative explanation is given in terms of the effective diffusion of the photogenerated carriers, determined by the experimental conditions, which influence the capture probability and hence also the charge state of the quantum dots. This is proposed as an effective tool to populate single quantum dots with extra electrons, by purely optical means, in order to study phenomena involving charged excitons.
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| 4. |
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| 5. |
- Karlsson, Fredrik, 1974-, et al.
(författare)
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Temperature influence on optical charging of self-assembled InAs/GaAs semiconductor quantum dots
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:19, s. 2952-2954
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Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that the photoluminescence spectra of single self-assembled InAs/GaAs quantum dots are very sensitive to excitation energy and crystal temperature. This is qualitatively explained in terms of the effective diffusivity of photogenerated particles, which affects the capture probability of the quantum dot. As a consequence, this opens the possibility of controlling the average number of excess electrons in the quantum dot by optical means. This technique may be used as a simple tool to create and study charged exciton complexes without any specially fabricated samples. ⌐ 2001 American Institute of Physics.
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| 6. |
- Karlsson, Fredrik, 1974-, et al.
(författare)
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The influence of carrier diffusion on the formation of charged excitons in InAs/GaAs quantum dots
- 2002
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - 1386-9477 .- 1873-1759. ; 13:2-4, s. 101-104
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Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that the photoluminescence spectra of single self-assembled quantum dots are very sensitive to the excitation energy and crystal temperature. A qualitative explanation is given in terms of the effective diffusivity of the photogenerated carriers, determined by the experimental conditions, which influence the capture probability and hence also the charge state of the quantum dots (QDs). This is proposed as an effective tool to populate quantum dots with extra electrons in order to study phenomena involving charged excitons. ⌐ 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
- Moskalenko, Evgenii, 2000-, et al.
(författare)
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Acceptor-induced threshold energy for the optical charging of InAs single quantum dots
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:19, s. 1953321-19533211
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Tidskriftsartikel (refereegranskat)abstract
- We study the photoluminescence of single InAs/GaAs self-assembled quantum dots for a range of excitation powers, excitation energies and sample temperatures 4 K30 K), this effect vanishes due to the essential decrease of the steady-state free electron concentration in the GaAs barrier as a result of thermally excited free holes appearing in the GaAs barrier valence band which provides an effective recombination channel for the free electrons. These experimental observations could be used as an effective tool to create and study charged excitons in quantum dots.
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| 8. |
- Moskalenko, Evgenii, 2000-, et al.
(författare)
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Effect of an additional infrared excitation on the luminescence efficiency of a single InAs/GaAs quantum dot
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:15, s. 1553171-15531714
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Tidskriftsartikel (refereegranskat)abstract
- Microphotoluminescence (PL) spectra of a single InAs/GaAs self-assembled quantum dot (QD) are studied under the main excitation of electron-hole pairs in the wetting layer (WL) and an additional infrared (IR) laser illumination. It is demonstrated that the IR laser with fixed photon energy well below the QD ground state induces striking changes in the spectra for a range of excitation energies and powers of the two lasers. For the main excitation above a threshold energy, defined as the onset of transitions between shallow acceptors and the conduction band in GaAs, the addition of the IR laser will induce a considerable increase in the QD emission intensity. This is explained in terms of additional generation of extra electrons and holes into the QD by the two lasers. For excitation below the threshold energy, the carrier capture efficiency from the WL into the QD is suggested to be essentially determined by the internal electric-field-driven carrier transport in the plane of the WL. The extra holes, generated in the GaAs by the IR laser, are supposed to effectively screen the built-in field, which results in a considerable reduction of the carrier collection efficiency into the QD and, consequently, a decrease of the QD PL intensity. A model is presented which allows estimating the magnitude of the built-in field as well as the dependence of the observed increase of the QD PL intensity on the powers of the two lasers. The use of an additional IR laser is considered to be helpful to effectively manipulate the emission efficiency of the quantum dot, which could be used in practice in quantum-dot-based optical switches.
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| 9. |
- Moskalenko, Evgenii, 2000-, et al.
(författare)
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Formation of the charged exciton complexes in self-assembled InAs single quantum dots
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:11, s. 6787-6793
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Tidskriftsartikel (refereegranskat)abstract
- The low-temperature photoluminescence (PL) of the self-assembled InAs single quantum dots (QD) was studied using micro-PL setup. It was demonstrated that two emission lines down shifted in energy with respect to the ground state exciton PL line appeared in the PL spectrum. The PL intensity of these lines showed a periodic behavior with the excitation energy.
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| 10. |
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| 11. |
- Moskalenko, Evgenii, 2000-, et al.
(författare)
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The effect of an additional infrared laser on the carrier collection efficiency of InAs quantum dots
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:24, s. 4896-4898
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Tidskriftsartikel (refereegranskat)abstract
- The impact of single and multi-quantum dots (QD) on the exposure by a low-energy laser was investigated using micro-photoluminescence. The presence of the low-energy laser effectively quenched the single QD luminescence, at low temperatures. An induced screening of a built-in electric field that played an important role as a carrier capture mechanism led to this effect. When the capture efficieny was increased by elevated crystal temperature, the influence of the low-energy laser decreased.
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