Relaxation of a strained quantum well at a cleaved surface

Davies, Julie; Bruls, DM Dominique; Vugs, Jwam; Koenraad, PM Paul

doi:10.1063/1.1459100

Cited by 38 publications

(30 citation statements)

References 11 publications

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“…9 for the outward relaxation of a quantum well, which assumes that the elastic response is linear and isotropic. The WL was modeled including the effect of the asymmetric As profile, which is likely created during the switching between phosphorus to arsenic flux or by As carryover.…”

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confidence: 99%

Capping of InAs quantum dots grown on (311)B InP studied by cross-sectional scanning tunneling microscopy

Çelebi

Ulloa

Koenraad

et al. 2006

Applied Physics Letters

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Cross-sectional scanning tunneling microscopy was used to study at the atomic scale the impact of the capping material on the structural properties of self-assembled InAs quantum dots (QDs) grown on a high index (311)B InP substrate. Important differences were found in the capping process when InP or lattice matched InGaAs(P) alloys are used. The QDs capped with InP have a smaller height due to As∕P exchange induced decomposition. This effect is not present when InGaAs is used as the capping material. However, in this case a strong strain driven phase separation appears, creating In rich regions above the QDs and degrading the dot/capping layer interface. If the InAs dots are capped by the quaternary alloy InGaAsP the phase separation is much weaker as compared to capping with InGaAs and well defined interfaces are obtained.

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confidence: 99%

Capping of InAs quantum dots grown on (311)B InP studied by cross-sectional scanning tunneling microscopy

Çelebi

Ulloa

Koenraad

et al. 2006

Applied Physics Letters

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“…The indium segregation profile of the WLs can be simply described by the phenomenological model of Muraki et al described in the previous section [27,31]. Based on this model, we calculated the outward relaxation of the WLs using the analytical expressions by Davies et al [24]. The optimal fit to the experimental relaxation profiles was obtained with N= (1.9 ± 0.1)ML, R = 0.79 ± 0.03 and N = (1.9 ± 0.1)ML, R = 0.78 ± 0.03 for the InAs WLs in GaAs and AlAs, respectively, where N is the total amount of deposited In and R the segregation coefficient.…”

Section: Figure 515 Calculated and Measured Relaxation Profiles Thromentioning

confidence: 99%

“…The measured outward displacement and strain (measured by the change in lattice spacing) can be used to determine the indium composition of a strained (In,Ga) As nanostructure, by comparing the experimental data with the calculated relaxation and strain using elasticity theory [24]. In the case of quantum wells with a low concentration of indium (<30%), or wetting layers, the indium distribution can also be obtained directly by counting the indium atoms, as will be shown in the next sections.…”

Section: Figure 54 Strain Relaxation At the Cleaved Surface Of A Strmentioning

confidence: 99%

“…The outward relaxation of the WL was again calculated by means of the analytical expression derived in [24], which assumes that the elastic response is linear and isotropic. The WL was modelled including the effect of the asymmetric As profile, which is likely created during the switching between phosphorus to arsenic flux or by As carryover [76].…”

Section: Capping With Lattice-matched Layersmentioning

confidence: 99%

“…By modelling the indium segregation, the outward displacement of the segregated WL can be calculated by integration of the analytical expression derived by Davies for the outward displacement of a cleaved quantum well [24]. Several models for indium segregation have been proposed [30][31][32][33].…”

Section: Formation Of the Wetting Layermentioning

confidence: 99%

See 2 more Smart Citations

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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Scanning spreading resistance microscopy of undoped CdS/ZnSSe multiple quantum well heterostructure

Sviridov

Kozlovsky

Sannikov

2010

Physica Status Solidi (b)

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We carried out scanning spreading resistance microscopy (SSRM) investigation of the undoped CdS/ZnSSe multiple quantum well (MQW) heterostructure under different illumination conditions. To study this effect we illuminated the probe-sample point contact with the radiation of a halogen lamp (HL) (hn ¼ 1.2-3.1 eV). In spite of the fact that the photon energy of the built-in atomic force microscope laser (BL) (1.9 eV) is smaller than the band gap energy of the CdS (2.46 eV) and the energy of transitions between ZnSSe valence band and CdS conduction band (2.2 eV) it, nevertheless, influences the visualization, possibly due to Franz-Keldysh effect. It was found that all layers of the structure can be visualized only under negative sample potential, indicating Schottky barrier formation at probe-sample contact. We estimated the carrier concentration in QWs on the basis of simple Schottky diode theory, taking into account spreading resistance R s .

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Relaxation of a strained quantum well at a cleaved surface

Cited by 38 publications

References 11 publications

Capping of InAs quantum dots grown on (311)B InP studied by cross-sectional scanning tunneling microscopy

Capping of InAs quantum dots grown on (311)B InP studied by cross-sectional scanning tunneling microscopy

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

Scanning spreading resistance microscopy of undoped CdS/ZnSSe multiple quantum well heterostructure

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