Determination of the shape and indium distribution of low-growth-rate InAs quantum dots by cross-sectional scanning tunneling microscopy

Bruls, Dominique; Vugs, Jwam; Koenraad, P. M.; Salemink, H.W.M.; Wolter, J.H.; Hopkinson, M.; Skolnick, M. S.; Long, Fei; Gill, S.P.A.

doi:10.1063/1.1504162

Cited by 207 publications

(93 citation statements)

References 16 publications

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“…"100… substrate a function of GI for both substrates. The PL energy is dependent on the size of the dots, the strain, the quantum dot composition, 10 etc., and is shifted to higher energies ͑ϳ1.25 eV͒ in comparison with that of bulk InAs (0.4 eV, Ref. 11), mainly due to strong charge confinement.…”

Section: Resultsmentioning

confidence: 99%

Magnetophotoluminescence study of the influence of substrate orientation and growth interruption on the electronic properties of InAs∕GaAs quantum dots

Godefroo

Maes

Hayne

et al. 2004

Journal of Applied Physics

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We have used photoluminescence in pulsed ͑ഛ50 T͒ and dc ͑ഛ12 T͒ magnetic fields to investigate the influence of substrate orientation and growth interruption (GI) on the electronic properties of InAs/ GaAs quantum dots, grown by molecular beam epitaxy at 480°C. Dot formation is very efficient on the ͑100͒ substrate: electronic confinement is already strong without GI and no significant change in confinement is observed with GI. On the contrary, for the ͑311͒B substrate strong confinement of the charges only occurs after a GI is introduced. When longer GIs are applied the dots become higher.

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Section: Resultsmentioning

confidence: 99%

Magnetophotoluminescence study of the influence of substrate orientation and growth interruption on the electronic properties of InAs∕GaAs quantum dots

Godefroo

Maes

Hayne

et al. 2004

Journal of Applied Physics

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“…9 Both XRD and XSTM suggest that the In composition varies with height through the QDs, with pure InAs at the top of the QDs and progressively more Ga in the alloy towards the base of the QDs. 7,8 This alloying effect depends on growth conditions, particularly temperature 2 and growth rate. 10 In this letter we describe the use of medium-energy ion scattering ͑MEIS͒ to produce composition profiles of InAs QDs.…”

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confidence: 99%

“…A linear variation with height in the QDs is assumed as the simplest nonconstant composition. 7,8 The contribution of the WL is important, particularly at the leading edge of the energy spectrum. The WL is expected to be an InGaAs alloy of thickness 1-2 ML, 1 and indeed the optimized WL comprises a 2 ML thick In 0.05 Ga 0.95 As alloy.…”

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confidence: 99%

“…[3][4][5] These processes are controlled by a complicated combination of surface segregation 6 and locally strain-dependent surface migration and attachment. 5 Several experimental techniques have been used to probe the In distribution in QDs, including grazing incidence x-ray diffraction ͑XRD͒, 7 cross-sectional scanning tunneling microscopy ͑XSTM͒, 5,8 transmission electron microscopy ͑TEM͒ and scanning TEM energy dispersive x-ray analysis. 9 Both XRD and XSTM suggest that the In composition varies with height through the QDs, with pure InAs at the top of the QDs and progressively more Ga in the alloy towards the base of the QDs.…”

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confidence: 99%

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Composition profiles of InAs–GaAs quantum dots determined by medium-energy ion scattering

Quinn

Wilson

Hatfield

et al. 2005

Applied Physics Letters

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“…This can also be seen by the slight asymmetry in the relaxation profile of the InAs/GaAs QD. From X-STM and photocurrent experiments, it has been shown that low-growth rate InAs/GaAs QDs have an increasing indium concentration in the growth direction [47,48]. However, other groups have reported InGaAs QDs with laterally non-uniform indium compositions showing an inverted-triangle, trumpet or truncated reversed-cone shape [26,[49][50][51].…”

Section: 14 Filled States Topography X-stm Image Of (A) Three Qd Laymentioning

confidence: 99%

InAs Quantum Dot Formation Studied at the Atomic Scale by Cross-sectional Scanning Tunnelling Microscopy

Ulloa

Offermans

Koenraad

2008

Handbook of Self Assembled Semiconductor Nanostructures for Novel Devices in Photonics and Electronics

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Introduction Quantum dot formationSelf-assembled quantum dots (QDs) have attracted much attention in the last years [1,2]. These nanostructures are very interesting from a scientific point of view because they form nearly ideal zero-dimensional systems in which quantum confinement effects become very important. These unique properties also make them very interesting from a technological point of view. For example, InAs QDs are employed in QD lasers [3,4], single electron transistors [5], midinfrared detectors [6,7], single-photon sources [8,9], etc. InAs QDs are commonly created by the Stranski-Krastanov growth mode when InAs is deposited on a substrate with a bigger lattice constant, like GaAs or InP [10]. Above a certain critical thickness of InAs, three-dimensional islands are spontaneously formed on top of a wetting layer (WL) to reduce the strain energy. Once created, the QDs are subsequently capped, a step which is required for any device application.For any application based on InAs QDs, an accurate control of their electronic properties is required. The electron and hole states in the dot are very sensitive to the QD size, shape and composition (as well as to the surrounding material), and therefore an accurate control of the QD structural properties is necessary for applications. This explains the strong effort dedicated in the last years to the structural characterization of QDs [11], which is essential in order to have a deep understanding of the QD formation process. Although a lot of effort has been dedicated to study surface QDs, there are relatively few studies focused on the effect of the capping process [12][13][14][15][16][17][18][19][20]. Some of these studies have already shown significant differences in size, shape and composition between uncapped and capped QDs. For example, an important collapse of the QD height has been reported for InAs/GaAs QDs capped with GaAs [14,15,[17][18][19], revealing the big influence of the capping process on the structural properties of the QDs. Indeed, critical issues affecting the dot take place during capping like dot decomposition, intermixing, segregation, As/P exchange and composition modulation in the capping layer. This means that the real buried QDs must be studied in order to understand the complete QD formation process. Cross-sectional scanning tunnelling microscopy is an especially useful technique for this purpose, because it allows the structure of the capped dots at the atomic scale to be assessed. Cross-sectional scanning tunnelling microscopy (X-STM)The scanning tunnelling microscope is part of the family of scanning probe microscopes, which are able to provide direct real space information of a physical property at the atomic scale. This

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Determination of the shape and indium distribution of low-growth-rate InAs quantum dots by cross-sectional scanning tunneling microscopy

Cited by 207 publications

References 16 publications

Magnetophotoluminescence study of the influence of substrate orientation and growth interruption on the electronic properties of InAs∕GaAs quantum dots

Magnetophotoluminescence study of the influence of substrate orientation and growth interruption on the electronic properties of InAs∕GaAs quantum dots

Composition profiles of InAs–GaAs quantum dots determined by medium-energy ion scattering

InAs Quantum Dot Formation Studied at the Atomic Scale by Cross-sectional Scanning Tunnelling Microscopy

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