Carrier dynamics in type-II GaSb/GaAs quantum dots

Hatami, Fariba; Grundmann, Marius; Ledentsov, N. N.; Heinrichsdorff, F.; Heitz, R.; Böhrer, J.; Bimberg, D.; Ruvimov, S.; Werner, P.; Ustinov, V. M.; Kop’ev, P. S.; Alfërov, Zh. I.

doi:10.1103/physrevb.57.4635

Cited by 247 publications

(169 citation statements)

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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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confidence: 69%

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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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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“…5 The exclusive confinement of holes and their large localization energy makes GaSb/GaAs QDs particularly interesting for charge storage devices. [6][7][8] GaSb/GaAs QDs were first grown using molecular beam epitaxy 2,9 and later by metal-organic chemical vapor epitaxy, 10,11 followed by optical characterization, 9,[12][13][14][15] cross-section scanning electron microscopy investigations, 16 and deep-level transient spectroscopy (DLTS) studies, 17,18 accompanied by numerical calculations. [19][20][21] The various investigations have been performed on different samples.…”

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confidence: 99%

Linking structural and electronic properties of high-purity self-assembled GaSb/GaAs quantum dots

et al. 2012

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Hayne, M. (2012). Linking structural and electronic properties of high-purity self-assembled GaSb/GaAs quantum dots. Physical Review B, 86(3) 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: www.tue.nl/taverne Take down policyIf you believe that this document breaches copyright please contact us at: openaccess@tue.nl providing details and we will investigate your claim. We present structural, electrical, and theoretical investigations of self-assembled type-II GaSb/GaAs quantum dots (QDs) grown by molecular beam epitaxy. Using cross-sectional scanning tunneling microscopy (X-STM) the morphology of the QDs is determined. The QDs are of high purity (∼100% GaSb content) and have most likely the shape of a truncated pyramid. The average heights of the QDs are 4-6 nm with average base lengths between 9 and 14 nm. Samples with a QD layer embedded into a pn-diode structure are studied with deep-level transient spectroscopy (DLTS), yielding a hole localization energy in the QDs of 609 meV. Based on the X-STM results the electronic structure of the QDs is calculated using 8-band k·p theory. The theoretical localization energies are found to be in good agreement with the DLTS results. Our results also allow us to estimate how variations in size and shape of the dots influence the hole localization energy.

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“…The structure of Sb-terminated GaAs(001) surdots on GaAs for potential use in optoelectronic devices [2][3][4][5]. In addition to forming an important faces is of interest for a variety of reasons.…”

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confidence: 99%