Tuning quantum dot properties by activated phase separation of an InGa(Al)As alloy grown on InAs stressors

Maximov, M. V.; Tsatsulnikov, A. F.; Volovik, B. V.; Sizov, D. S.; Shernyakov, Yu. M.; Kaiander, I.; Zhukov, A. E.; Kovsh, A. R.; Mikhrin, S. S.; Ustinov, V. M.; Alfërov, Zh. I.; Heitz, R.; Shchukin, V. A.; Ledentsov, N. N.; Bimberg, D.; Musikhin, Yu. G.; Neumann, Wolfgang

doi:10.1103/physrevb.62.16671

Cited by 209 publications

(100 citation statements)

References 45 publications

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“…This interpretation is in agreement with previously reported results in which QDs capped with InGaAs instead of GaAs are shown to retain their shape during the initial stages of capping [71,72]. It could be argued that the increase in dot height is due to strain induced compositional modulation in the capping layer [68]. Although part of the increase in dot height could be due to that effect, we think that its contribution should be very small, since no traces of compositional modulation are observed in the capping layer.…”

Section: Ingaas Capping Of Inas/gaas Qdssupporting

confidence: 82%

“…This phase separation is a strain-driven process in which the In adatoms on the growth surface migrate towards the regions on top of the dots to minimize the strain, creating a columnar-like In-rich region above the dots. This process has been observed in columnar InGaAs QDs grown on GaAs [81], as well as in InAs/GaAs QDs, where capping with InGaAs has been shown to induce an increase in the dot size [68]. In our case, the phase separation directly affects the QDs by creating a rough top interface in which the In content decreases gradually.…”

Section: Capping With Lattice-matched Layersmentioning

confidence: 69%

See 1 more Smart Citation

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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Section: Ingaas Capping Of Inas/gaas Qdssupporting

confidence: 82%

Section: Capping With Lattice-matched Layersmentioning

confidence: 69%

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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“…It has been demonstrated in the context of QD lasers and LEDs that the use of InGaAs or InAlGaAs SRLs is an effective method to redshift [24][25][26][27][28] …”

Section: Ill Sample Descriptionmentioning

confidence: 99%

Reducing carrier escape in the InAs/GaAs quantum dot intermediate band solar cell

Antolín

Martı́

Farmer

et al. 2010

Journal of Applied Physics

165

136

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Intermediate band solar cells (IBSCs) fabricated to date from In(Ga)As/GaAs quantum dot arrays (QD-IBSC) exhibit a quantum efficiency (QE) that extends to below bandgap energies. However, the production of sub-bandgap photocurrent relies often on the thermal and/or tunneling escape of carriers from the QDs, which is incompatible with preservation of the output voltage. In this work, we test the effectiveness of introducing a thick GaAs spacer in addition to an InAlGaAs strain relief layer (SRL) over the QDs to reduce carrier escape. From an analysis of the QE at different temperatures, it is concluded that escape via tunneling can be completely blocked under short-circuit conditions, and that carriers confined in QDs with an InAlGaAs SRL exhibit a thermal escape activation energy over 100 meV larger than in the case of InAs QDs capped only with GaAs.

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“…This process has been observed in columnar InGaAs QDs grown on GaAs, 15 as well as in InAs/ GaAs QDs, where capping with InGaAs has been shown to induce an increase of the dot size. 16 In our case, the phase separation directly affects the QDs by creating a rough top interface in which the In content decreases gradually. InGaAs seems therefore to be less suitable capping material for InAs QDs grown on InP ͑311͒B substrate.…”

mentioning

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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Tuning quantum dot properties by activated phase separation of an InGa(Al)As alloy grown on InAs stressors

Cited by 209 publications

References 45 publications

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

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

Reducing carrier escape in the InAs/GaAs quantum dot intermediate band solar cell

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

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