Observation of strain effects in semiconductor dots depending on cap layer thickness

Pistol, Mats‐Erik; Carlsson, N.; Persson, Christer; Seifert, Werner; Samuelson, Lars

doi:10.1063/1.114519

Cited by 68 publications

(41 citation statements)

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“…6 Similar results have been observed for other systems such as InAs/GaAs, 6 InGaAs/GaAs, 7 and InP/InGaP. 9 We should also consider the contribution of the intermixing at the interfaces, which results in a blue shift. However, a detailed information of the effect of the capping layer on the optical emission of the QDs is still under progress.…”

Section: A Structural Analysissupporting

confidence: 57%

“…Previous studies using uncapped SAQDs have indeed observed weaker photoluminescence ͑PL͒ as compared to capped dots on systems such as InAs/GaAs, 6 InGaAs/GaAs, 7 Ge/Si, 8 and InP/InGaP. 9 In contrast, uncapped InP/GaAs SAQDs present an efficient PL emission that allows us to obtain structural and optical properties from the same sample, which is actually a very important advantage when investigating SAQD properties.…”

Section: Introductionmentioning

confidence: 99%

“…The efficient optical emission in uncapped QDs has also been observed in a previous work for InP/InGaP SAQDS. 9 Surface states usually work as efficient nonradiative channels for the photocreated carriers. The surface recombination velocity for In-based compounds such as InP, [15][16][17][18] is significantly smaller than that for GaAs.…”

Section: A Structural Analysismentioning

confidence: 99%

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Structural and optical properties of InP quantum dots grown on GaAs (001)

Godoy

Nakaema

Lopes

et al. 2007

Phys. Status Solidi (c)

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We investigated structural and optical properties of type-II InP/GaAs quantum dots using reflection high energy electron diffraction, transmission electron microscopy, atomic force microscopy, grazing incidence x-ray diffraction, and photoluminescence techniques. The InP dots present an efficient optical emission even when they are uncapped, which is attributed to the low surface recombination velocity in InP. We compare the difference in the optical properties between surface free dots, which are not covered by any material, with dots covered by a GaAs capping layer. We observed a bimodal dispersion of the dot size distribution, giving rise to two distinct emission bands. The results also revealed that the strain accumulated in the InP islands is slightly relieved for samples with large InP amounts. An unexpected result is the relatively large blue shift of the emission band from uncapped samples as compared to capped dots.

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Section: A Structural Analysissupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: A Structural Analysismentioning

confidence: 99%

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Structural and optical properties of InP quantum dots grown on GaAs (001)

Godoy

Nakaema

Lopes

et al. 2007

Phys. Status Solidi (c)

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“…It has been shown that for coherently grown self-assembled quantum dots the strain state inside the dot depends on the cap layer thickness. 17 In the capped dots the strain in the dots has hydrostatic and biaxial components. The presented dots are not coherently grown and the strain in the buried dots should be more hydrostatic than biaxial, contrary to what has been observed in coherently grown systems.…”

Section: Discussionmentioning

confidence: 99%

Raman scattering of InSb quantum dots grown on InP substrates

Armelles

Utzmeier

Postigo

et al. 1997

Journal of Applied Physics

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In this paper we present the Raman scattering of self-assembled InSb dots grown on ͑001͒ oriented InP substrates. The samples were grown by pulsed molecular beam epitaxy mode. Two types of samples have been investigated. In one type the InSb dots were capped with 200 monolayers of InP; in the other type no capping was deposited after the InSb dot formation. We observe two peaks in the Raman spectra of the uncapped dot, while only one peak is observed in the Raman spectra of the capped dots. In the case of the uncapped dots the peaks are attributed to LO-like and TO-like vibration of completely relaxed InSb dots, in agreement with high resolution transmission electron microscopy photographs. The Raman spectra of the capped dot suggest a different strain state in the dot due to the capping layer.

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“…Light absorption at the E 1 and E 1 1 D 1 critical points of InSb islands buried in InP disappears for nominal InSb thicknesses lower than 10 monolayers as a consequence of the strain produced inside the islands by the cap layer. Certainly, this strain increases as the InSb deposition diminishes, changing the band lineup of the system from type-I to type-II and therefore drastically reducing the oscillator strengths of the island-related E 1 and E 1 1 D 1 transitions.[ S0031-9007(97) [2,3] of islands in self-assembled quantum dot (QD) structures, but also in the physical properties and, in particular, in the optical properties of such systems [4][5][6][7][8]. All previous studies considered only the strain-induced change of the energies of the island-related optical transitions, but strain also modifies the energies of the electronic states of the dots with respect to those of the matrix.…”

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confidence: 99%

Strain-Induced Quenching of Optical Transitions in Capped Self-Assembled Quantum Dot Structures

Prieto¹,

Armelles²,

Utzmeier³

et al. 1998

Phys. Rev. Lett.

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Strain-induced quenching of optical transitions has been found in capped self-assembled quantum dot structures. Light absorption at the E 1 and E 1 1 D 1 critical points of InSb islands buried in InP disappears for nominal InSb thicknesses lower than 10 monolayers as a consequence of the strain produced inside the islands by the cap layer. Certainly, this strain increases as the InSb deposition diminishes, changing the band lineup of the system from type-I to type-II and therefore drastically reducing the oscillator strengths of the island-related E 1 and E 1 1 D 1 transitions.[ S0031-9007(97) [2,3] of islands in self-assembled quantum dot (QD) structures, but also in the physical properties and, in particular, in the optical properties of such systems [4][5][6][7][8]. All previous studies considered only the strain-induced change of the energies of the island-related optical transitions, but strain also modifies the energies of the electronic states of the dots with respect to those of the matrix. In this paper we present a new effect related to the builtin strain characteristic of self-assembled QD structures: The quenching of optical transitions produced by a straininduced modification of the band lineup of the system. InSb dots grown on top of InP and InSb dots grown deeply buried in InP are the objects of study of this paper. Different modulation spectroscopies were used for optical characterization and transmission electron microscopy (TEM) and Raman scattering for structural characterization.Uncapped (dots on top) and capped (dots deeply buried) samples were grown by molecular-beam epitaxy [9], under identical conditions, on semi-insulating (001) InP substrates. Growth details are reported elsewhere [10]. The nominal InSb thicknesses were 2.2, 3.2, 5, and 7 monolayers (ML) in the uncapped samples and 3.5, 5, 10, and 15 ML in the capped samples, in which the cap layer thickness was 150 ML. Doubtless due to the large lattice mismatch existing between InSb and InP ͑ഠ10.4%͒, the onset of the island growth mode was observed after growing only 1.2 ML of InSb. In consequence, well-developed dots were obtained in every sample, as TEM results presented below demonstrate. The typical island size was of the order of several tens of nanometers. Figure 1 shows photoreflectance spectra from uncapped [1(a)] and capped [1(b)] samples recorded at 80 K paying attention to the island-related E 1 and E 1 1 D 1 transitions, which are associated with the corresponding critical points of the dots. Measurements on both kinds of samples were carried out under identical conditions in order to obtain comparable results. As can be observed, in uncapped samples the studied transitions are perfectly detectable even for nominal InSb thicknesses as small as 3.2 ML (some signal was barely detected in the 2.2 ML sample). Strikingly, in capped samples the studied transitions are not detectable by any means for nominal InSb thicknesses lower than 10 ML (also, no signal was detected in the 3.5 ML sample). The less InSb grown the smaller the...

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Observation of strain effects in semiconductor dots depending on cap layer thickness

Cited by 68 publications

References 0 publications

Structural and optical properties of InP quantum dots grown on GaAs (001)

Structural and optical properties of InP quantum dots grown on GaAs (001)

Raman scattering of InSb quantum dots grown on InP substrates

Strain-Induced Quenching of Optical Transitions in Capped Self-Assembled Quantum Dot Structures

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