| 1. |
- Borgström, Magnus, et al.
(författare)
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InAs quantum dots grown on InAlGaAs lattice matched to InP
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 252:4, s. 481-485
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present InAs quantum dots prepared on an InxAlyGa1-x-yAs surface by metal organic vapor phase epitaxy. Atomic force microscopy measurements indicate that dots grown on material with higher Al content are smaller, and that the local dot densities on step-bunched facets formed on the vicinal (0 0 1) surfaces increase. We find that these dots show luminescence at very long wavelengths, lambda(room temperature) approximate to 2.1 mum, and that the emission wavelengths are blue-shifted when the Al content is increased in the layer onto which dot material is deposited. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 2. |
- Borgström, Magnus, et al.
(författare)
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Site control of InAs quantum dots on a patterned InP surface: As/P exchange reactions
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 248, s. 310-316
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Tidskriftsartikel (refereegranskat)abstract
- In this paper. we present the effect of annealing temperature and annealing time on InAs site-controlled quantum dot growth. Individual InAs quantum dots formed by self-assembling have been positioned into holes, created by partial overgrowth of electron beam induced nano-carbon deposits by metal organic vapor phase epitaxy. As/P exchange reactions produce material sufficient for selective dot nucleation in the holes. Results. showing that As/P exchange reactions occur even when capping the dots with InP are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Carlsson, N, et al.
(författare)
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IMPROVED SIZE HOMOGENEITY OF INP-ON-GAINP STRANSKI-KRASTANOW ISLANDS BY GROWTH ON A THIN GAP INTERFACE LAYER
- 1995
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 156:1-2, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- Coherent InP nano-sized islands, embedded into GaInP, have been grown by metal-organic vapour phase epitaxy using the Stranski-Krastanow growth mode. Photoluminescence, atomic force microscopy and transmission electron microscopy studies show that the insertion of a thin ∼ 4 monolayer thick GaP layer affects the critical thickness of the subsequently deposited two-dimensional InP wetting layer, increasing it from ∼ 1.5 monolayers (without an inserted GaP layer) to ∼ 2.5 monolayers (with an inserted GaP layer). We demonstrate that the inserted GaP layer affects also the island formation. The bimodal size distribution of Stranski-Krastanow islands, typical for low InP coverages, can be overcome without island coalescence by deposition on top of the thin GaP layer, where a coverage of InP of about 3.5–4.5 monolayers results in the formation of almost only the larger, fully developed, pyramidal islands. Annealing experiments at growth temperature of 580°C show that these islands (base area ≈ 40 × 50 nm2, height ≈ 10–15 nm, surface density ≈ (1−2) × 109 cm−2) are rather stable in a time-scale over several minutes before they slowly undergo an Ostwald ripening process.
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| 4. |
- Ferdos, Fariba, 1966, et al.
(författare)
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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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| 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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| 6. |
- Håkansson, G., et al.
(författare)
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Ion irradiation effects during growth of Mo/V(001) superlattices by dual-target magnetron sputtering
- 1992
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 121:3, s. 399-412
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial (001)-oriented Mo/V superlattice films with wavelengths of ≈ 5 nm have been grown on MgO(001) substrates, kept at 700°C, by dual-target unbalanced magnetron sputter deposition in Ar discharges. Low-energy (15-250 eV) Ar ion irradiation with incident ion-to-metal flux ratio of ≈ 1 during film growth was obtained through the application of a negative potential Vs to the substrate. The effects of ion bombardment on interface roughness and mixing, resputtering rates, and defect structure were investigated using a combination of cross-sectional transmission electron microscopy (XTEM), X-ray diffraction (XRD), and simulation of XRD patterns. High-resolution XTEM images showed that the interfaces were relatively sharp for Vs ≤ 100 V while higher Vs values resulted in more diffuse interfaces indicating ion-induced intermixing. By using a kinematical model of diffraction, and comparing with experimental XRD results, it could be concluded that the intermixing increased from ≈ 0.3 nm (2 monolayers) at Vs = 15 V to & 0.9 nm (6 monolayers) at Vs = 250 V. The inhomogeneous strain showed a large increase for Vs & 50 V. This is explained by an incorporation of point defects. Coherency strain relaxation between layers is suggested to take place through the formation of edge dislocations with Burgers vector 〈110〉 by climb processes. Finally, increasing Vs also resulted in resputtering, preferentially from the V layers.
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| 7. |
- Johansson, Jonas, et al.
(författare)
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Kinetics of self-assembled island formation: Part I - Island density
- 2002
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 234:1, s. 132-138
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Tidskriftsartikel (refereegranskat)abstract
- We present a rate equation model for self-assembled quantum dot formation, or Stranski-Krastanow growth. The model includes a kinetically defined critical wetting layer thickness and a subsequent wetting layer decomposition. With these rate equations, total island densities can be calculated under varying deposition conditions, i.e., temperature and deposition rate.
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| 8. |
- Johansson, Jonas, et al.
(författare)
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Kinetics of self-assembled island formation: Part II - Island size
- 2002
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 234:1, s. 139-144
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a simple and intuitive way to predict self-assembled island sizes for varying deposition conditions, i.e., temperature and deposition rate. The average island size and the modality of the size distribution (unimodal with large or small islands, or bimodal) is calculated via materials balancing over a total island density (known by experiments or from nucleation calculations). We also find that there is a density interval in which the size distribution is bimodal. The width of this interval increases with the total amount of material in the islands. The borders of the interval change with the sizes of the small and large islands, which can also change the interval width. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 9. |
- Petfordlong, Amanda K., et al.
(författare)
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On the growth of small crystals of Cd, Zn, Pt and Rh during electron microscope observations
- 1987
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 80:2, s. 218-224
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Tidskriftsartikel (refereegranskat)abstract
- The growth of small supported metal crystals under the influence of an electron beam has been studied in real-time using a 400 keV ultra-high-resolution electron microscope. Samples of Pt, Rh, Cd and Zn supported on amorphous C or Si films were prepared ex situ and crystal growth in situ was recorded directly using a TV imaging/video system attached to the microscope. The different types of observed crystal growth are reported: the fcc metals (Pt and Rh) grow by coalescence, or by the addition of atoms along the particle surface followed by structural rearrangements which result in approximately spherical particles. The hcp metals (Cd and Zn) grow in the form of long rafts along the surface of the substrate film.
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| 10. |
- Sass, T, et al.
(författare)
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Strain in GaP/GaAs and GaAs/GaP resonant tunnelling heterostructures
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 248, s. 375-379
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Tidskriftsartikel (refereegranskat)abstract
- We studied the morphology of GaP/(001)GaAs and GaAs/(001)GaP heterostructures grown by metal-organic vapour-phase epitaxy and found wire-like surface undulations elongated in the [110] direction. We attribute this elongation to anisotropic lateral growth rates in the [110] and [110] directions, which are due to a different roughness of monolayer surface steps. In III-V materials grown by molecular beam epitaxy. such surface corrugations are usually elongated in [110]. We explain this difference by the two growth methods having inverted ratios of lateral growth rates in [110] and [110]. Resonant tunnelling diodes fabricated from the GaP/GaAs heterostructures showed very symmetric I-V characteristics. Their peak-to-valley ratio was limited to 2. most probably due to the corrugation of the GaP barriers. (C) 2002 Elsevier Science B.V. All rights reserved.
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