Optical transitions in type-II InAs∕GaAs quantum dots covered by a GaAsSb strain-reducing layer

Jin, Chao-Yuan; Liu, H. Y.; Zhang, S. Y.; Jiang, Qi; Liew, S. L.; Hopkinson, M.; Badcock, T. J.; Nabavi, Elham; Mowbray, D. J.

doi:10.1063/1.2752778

Cited by 79 publications

(75 citation statements)

References 19 publications

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“…Here, it should be noted that, in the whole investigated range, the linear fit is nearly perfect for the QD emission, with no inflection points that could be attributed to excited states band filling, as noted by other authors. 2,9 Our result rather indicates that the larger charge density accumulation around the QDs could be related to intrinsic carrier dynamics of the system. However, a definite statement about the role played by the excited states is not possible in our case given the large inhomogeneous broadening of the QD emission band.…”

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“…Figure 1͑c͒ also shows that the emission bands grow approximately linear with the number of photons and, therefore, that electron-hole pairs are rapidly captured in their potential minima. 9 Above 60 mW, the WL intensity exhibits signatures of saturation, which are not present in the QD band. This behavior has been observed before in GaAsSb/ GaAs type II QWs, 6 and related to accumulation of electrons in the thick ͑5 nm͒ GaAsSb regions.…”

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confidence: 99%

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Optical investigation of type II GaSb∕GaAs self-assembled quantum dots

Alonso-Álvarez¹,

Alén²,

García³

et al. 2007

Applied Physics Letters

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We have studied the emission and absorption properties of type II GaSb/ GaAs quantum dots embedded in a p-i-n photodiode. The excitation power evolution provides clear signatures of the spatially separated confinement of electrons and holes in these nanostructures. We have estimated the confinement potential for the holes to be ϳ500 meV, leading to an intense room temperature emission assisted by recapture processes from the wetting layer. Photocurrent measurements show strong absorption in the wetting layer and in the quantum dots at room temperature which are important for photodetection applications based in this system. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2827582͔In recent years, GaSb/ GaAs structures have aroused great interest due to their type II band alignment and intrinsically different behavior compared to the well known InAs/ GaAs system. Fundamental issues regarding their growth process, energy level structure, and optical properties in addition to their technological applications in photodetection and photovoltaics have been already investigated in different configurations such as quantum dots ͑QDs͒, 1-5 quantum wells 6 ͑QWs͒ or ternary compounds. 7 In this work, we present various results regarding the GaSb/ GaAs QDs system, which extend and complete previous works.The QDs studied here were grown by solid source molecular beam epitaxy on a n-type GaAs͑001͒ substrate after deposition of a n-type GaAs buffer layer ͑Si: 1 ϫ 10 18 cm −2 ͒. The QDs were nucleated at 480°C, using a growth rate of 0.1 ML/ s. The formation of the GaSb QDs was detected by the change of the reflection high energy electron diffraction pattern after the deposition of 1.3 ML of GaSb. The GaSb layer, with a nominal thickness of 2 ML, was then exposed to Sb flux for 20 s and then annealed for 20 s without an Sb flux to limit the amount of Sb segregated during capping. The GaAs capping was done at 0.4 ML/ s in two steps. In the first step, a 10 nm thick GaAs layer was grown at the temperature of QD nucleation to avoid their destabilization. In the second one, a 40 nm thick GaAs layer was deposited at 570°C. During growth, the As and Sb beam equivalent pressures were 1.0ϫ 10 −5 and 1.9ϫ 10 −6 mbar, respectively. This scheme was repeated six times, with a 3 min growth interruption under an As 4 flux to lower the substrate temperature before the nucleation of the next QD layer. On top, a p-type 300 nm thick GaAs layer ͑Be: 1 ϫ 10 18 cm −2 ͒ was grown at 580°C. Finally, standard optical lithography and wet etching techniques were used to define mesas and metal Ohmic contacts. Figure 1͑a͒ shows the photoluminescence ͑PL͒ spectra recorded at 20 K as a function of excitation power at 532 nm. We can clearly identify two bands centered at 1.32 and 1.05 eV. The narrow high energy band corresponds to the wetting layer ͑WL͒ recombination and dominates the spectrum at low temperatures. Its peak energy position is compatible with a GaSb WL thickness of 0.7 nm, 2 which is larger than the total amount of GaSb deposited ͑0.57 nm͒...

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confidence: 99%

Optical investigation of type II GaSb∕GaAs self-assembled quantum dots

Alonso-Álvarez¹,

Alén²,

García³

et al. 2007

Applied Physics Letters

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“…[27][28][29][30][31][32] Because Sb is known to act as a surfactant, a GaSbAs SRL may act to suppress defect generation and enhance radiative recombination. 33 Furthermore the GaAsSb capping offers an additional degree of freedom as emission can come from type II band alignment.…”

Section: Role Of Segregation In Inas/gaas Quantum Dot Structures Cappmentioning

confidence: 99%

Role of segregation in InAs/GaAs quantum dot structures capped with a GaAsSb strain-reduction layer

et al. 2009

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Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: We report a combined experimental and theoretical analysis of Sb and In segregation during the epitaxial growth of InAs self-assembled quantum dot structures covered with a GaSbAs strain-reducing capping layer. Cross-sectional scanning tunneling microscopy shows strong Sb and In segregation which extends through the GaAsSb and into the GaAs matrix. We compare various existing models used to describe the exchange of group III and V atoms in semiconductors and conclude that commonly used methods that only consider segregation between two adjacent monolayers are insufficient to describe the experimental observations. We show that a three-layer model originally proposed for the SiGe system ͓D. J. Godbey and M. G. Ancona, J. Vac. Sci. Technol. A 15, 976 ͑1997͔͒ is instead capable of correctly describing the extended diffusion of both In and Sb atoms. Using atomistic modeling, we present strain maps of the quantum dot structures that show the propagation of the strain into the GaAs region is strongly affected by the shape and composition of the strain-reduction layer.

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“…The photoluminescence (PL) efficiency of GaSb/GaAs QDs, probably the most studied III-V type-II QD system, is typically much weaker than that of standard type-I QDs grown on GaAs, and very often the emission from the QDs is even weaker than the emission of the wetting layer (WL). 8,9 For this reason, there have been almost no reports on type-II QD lasers, 4,10 although many groups have demonstrated lasing from type-II QWs. 11,12 Therefore, III-V type-II QDs with good optical properties are still required to fully exploit their advantages in device applications.…”

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High efficient luminescence in type-II GaAsSb-capped InAs quantum dots upon annealing

Ulloa

Llorens²,

Alén³

et al. 2012

Applied Physics Letters

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Polarization-resolved resonant fluorescence of a single semiconductor quantum dot Appl. Phys. Lett. 101, 251118 (2012) Optical cavity efficacy and lasing of focused ion beam milled GaN/InGaN micropillars J. Appl. Phys. 112, 113516 (2012) Competitive carrier interactions influencing the emission dynamics of GaAsSb-capped InAs quantum dots Appl. Phys. Lett. 101, 231109 (2012) Fluorescence quantum efficiency of CdSe/ZnS quantum dots embedded in biofluids: pH dependence J. Appl. Phys. 112, 104704 (2012) Modification of the conduction band edge energy via hybridization in quantum dots

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Optical transitions in type-II InAs∕GaAs quantum dots covered by a GaAsSb strain-reducing layer

Cited by 79 publications

References 19 publications

Optical investigation of type II GaSb∕GaAs self-assembled quantum dots

Optical investigation of type II GaSb∕GaAs self-assembled quantum dots

Role of segregation in InAs/GaAs quantum dot structures capped with a GaAsSb strain-reduction layer

High efficient luminescence in type-II GaAsSb-capped InAs quantum dots upon annealing

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