| 1. |
- Lu, W., et al.
(författare)
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Application of combinatorial material chip method on the improvement of quantum dots emission efficiency
- 2004
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5277:1, s. 99-108
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Konferensbidrag (refereegranskat)abstract
- The combinatorial material chip method has been used to study the emission efficiency of InAs/GaAs quantum dots. The photoluminescence spectroscopy is performed to obtain the rule of emission efficiency on the proton implantation dose. A pronounced enhancement of room temperature emission efficiency has been obtained by the optimized quantum dots process condition. The increment of emission efficiency up to 80 itmes has been observed. This effect may be resulted from both the proton passivation and carrier capture enhancement effects. The maximum photoluminescence peak shift is about 23 meV resulted from the intermixing of quantum dots. A linear dependence behavior has been observed for both the non-radiative recombination time and carrier relaxation time on the ion-implantation dose. The maximum enhancement of the photoluminescence is observed in the proton implantation dose of 1.0 x 1014 cm-2 followed by rapid thermal annealing at 700°C. These effects will be useful for the QDs' optoelectronic devices.
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| 2. |
- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of a thin GaAs cap layer on structural and optical properties of InAs quantum dots
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:7, s. 1195-7
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Tidskriftsartikel (refereegranskat)abstract
- In this letter we investigate the changes in the surface morphology and emission wavelength of InAs quantum dots (QDs) during initial GaAs encapsulation by atomic force microscopy and photoluminescence. The density (2.9×1010 cm-2) and height (7.9±0.4 nm) of the uncapped QDs decrease and saturate at 0.6×1010 cm-2 and 4 nm, respectively, after the deposition of 4 monolayers (MLs) of GaAs. A model for the evolution of surface morphology is proposed. Photoluminescence spectra of the surface dots show a wavelength shift from 1.58 to 1.22 ?m when the GaAs capping layer thickness increases from 0 to 8 MLs.
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| 3. |
- Ferdos, Fariba, 1966, et al.
(författare)
-
Influence of initial GaAs and AlAs cap layers on InAs quantum dots grown by molecular beam epitaxy
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 251:1-4, s. 145-9
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Tidskriftsartikel (refereegranskat)abstract
- Capping of InAs quantum dots (QDs) with AlAs or GaAs causes a significant change in the structural properties of the QDs. However, there is a basic difference between these two capping materials. The GaAs capping causes a dramatic reduction of the dot density and height. AlAs capping, on the other hand, results in a partly suppressed height reduction and a higher dot density.
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| 4. |
- Ferdos, Fariba, 1966, et al.
(författare)
-
Influence of thin GaAs and AlAs cap layers on the structural properties of InAs quantum dots grown by molecular beam epitaxy
- 2002
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Ingår i: International Conference on Molecular Beam Epitaxy, 2002. ; , s. 285-6
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Konferensbidrag (refereegranskat)abstract
- Self-organised InAs quantum dots (QDs) are used as optical gain material in long wavelength lasers on GaAs. The measured QD height and density are often used as figures of merits, and great efforts have been made to maximise these two parameters to extend the wavelength coverage. In this work, we investigate the influence of initial GaAs and AlAs cap layers on the structural properties of InAs QDs. The study clearly shows that capping of InAs QDs causes a strong modification of not only the QD shape and height but also the QD density
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| 5. |
- Ferdos, Fariba, 1966, et al.
(författare)
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Optimisation of MBE growth conditions for InAs quantum dots on (001) GaAs for 1.3 μm luminescence
- 2001
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 227-228, s. 1140-5
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the optimised growth conditions for InAs quantum dots (QDs) grown on GaAs substrates by solid source molecular beam epitaxy (SSMBE). Growth conditions for best luminescence intensity and linewidth were found within narrow windows of substrate temperature (500-520°C) and nominal InAs layer thickness (3.3-3.7 monolayers). The emission wavelength of such InAs QDs capped by GaAs was around 1.24 ?m. However, this is redshifted to 1.3 ?m or more by capping the InAs QDs with a thin layer of InxGa1-xAs. The results show that both In content and thickness of the capping layer can be used to tune the emission wavelength. Atomic force microscopy images show that the surface recovers to two-dimensional when depositing In0.2Ga0.8As while remaining three-dimensional when depositing In0.4Ga0.6As.
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