Discrete monolayer light emission from GaSb wetting layer in GaAs

Lo, Ming Cheng; Huang, Shyh-Jier; Lee, Chien-Ping; Lin, Sheng-Di; Yen, Shun-Tung

doi:10.1063/1.2748087

Cited by 17 publications

(11 citation statements)

References 13 publications

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“…21 Indeed, the formation of GaSb islands on GaAs requires the initial deposition of a critical number of GaSb MLs on GaAs, reported to be less than 3 ML. 22,23 Since no Moir e fringes are visible in between the GaSb islands, the wetting layer is believed to be coherent. Fig.…”

Section: Methodsmentioning

confidence: 99%

Growth and strain relaxation of GaAs and GaP nanowires with GaSb shells

Salehzadeh

Kavanagh

Watkins

2013

Journal of Applied Physics

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We report on the growth of GaSb shells on Au-catalyzed GaAs or GaP nanowires (NWs) using metalorganic vapor phase epitaxy. The large lattice mismatch between GaSb and GaAs (GaP), 7.8% (11.8%), results in surface roughening and GaSb island formation via the Stranski-Krastanov (S-K) growth mode. Based on transmission electron microscopy (TEM) analysis, coherent GaSb islands on GaAs NWs could be grown up to a thickness of 1.8 nm for a core diameter of 34 ± 5 nm. For greater shell thickness of 9 ± 3 nm, equal axial and radial strain relaxation occurred increasing from 74% ± 3% for GaAs/GaSb NWs and 91% ± 2% for GaP/GaSb NWs to 100% with increasing core diameter from 15 ± 2 nm to 55 ± 3 nm. Axial strain is relieved by periodic misfit dislocations with edge components parallel to the growth direction. Tangential relaxation is presumed to occur partially by roughening via the S-K growth mode but dislocations with edge components perpendicular to the growth direction were not detected. Raman scattering measurements were performed on ensembles of NWs and the absolute residual strain in the core and shell were determined from the shift of the zone-center phonon modes. Raman results were consistent with the TEM analysis. It was found that the residual strain is higher in GaAs/GaSb NWs (7.3%) compared to GaP/GaSb NWs (1.7%).

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Section: Methodsmentioning

confidence: 99%

Growth and strain relaxation of GaAs and GaP nanowires with GaSb shells

Salehzadeh

Kavanagh

Watkins

2013

Journal of Applied Physics

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“…[2][3][4] Jiang et al 5 studied by atomic force microscopy ͑AFM͒ uncapped GaSb quantum dots grown by molecular beam epitaxy ͑MBE͒ and they found quantum dots sizes of about 10 nm. Nevertheless, during the process of capping of the GaSb with GaAs, an important fraction of the formed quantum dots seems to disappear, probably due to the exchange reaction of Sb adatoms with As atoms on the GaAs surface layer.…”

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confidence: 99%

High resolution electron microscopy of GaAs capped GaSb nanostructures

Molina

Beltrán

Ben

et al. 2009

Applied Physics Letters

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We show in this work that GaAs capping of 2 ML of GaSb grown by molecular beam epitaxy results in the formation of very small ͑with heights of about 1 nm͒ GaAs x Sb 1−x nanostructures surrounded by a GaAs rich layer. This conclusion is obtained by analyzing the morphology of the GaAs x Sb 1−x nanostructures by high resolution scanning transmission electron microscopy in Z-contrast mode. This result shows that a significant fraction of the Sb atoms must segregate along the growth direction during the GaAs capping process. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3077009͔Research on GaSb/GaAs quantum dots is a topic of increasing interest because this material has very attractive properties, such as its type-II band alignment, 1 opening the possibility to fabricate new devices such as quantum information devices and memories based on quantum dots. 2-4Jiang et al.5 studied by atomic force microscopy ͑AFM͒ uncapped GaSb quantum dots grown by molecular beam epitaxy ͑MBE͒ and they found quantum dots sizes of about 10 nm. Nevertheless, during the process of capping of the GaSb with GaAs, an important fraction of the formed quantum dots seems to disappear, probably due to the exchange reaction of Sb adatoms with As atoms on the GaAs surface layer. 6,7 This idea is supported by the fact that very small ͑approximately 1-2 nm in size͒ GaAs capped GaSb/GaAs nanostructures are observed by cross-sectional scanning tunneling microscopy on samples grown by metalorganic chemical vapor deposition at 470°C. In this work, we investigate by high resolution Z-contrast the nanomorphology of GaAs capped GaSb nanostructures grown at 480°C by MBE. The analysis of the photoluminescence spectra of these nanostructures in a previous work shows evidence of a type-II band alignment, with holes strongly confined ͑501 meV͒ and electrons weakly confined ͑46 meV͒ in the electrostatic potential created by the accumulation of multiple holes inside each quantum dot under optical pumping. The quantum dot photoluminescence at 1057 meV blueshifts as the excitation power is increased.8 Here we present a structural characterization study showing that GaAs capping of GaSb quantum dots results in the formation of very small ͑with heights of about 1 nm͒ nanostructures at the GaAs/ GaSb interface.The analyzed nanostructures were grown by solid source MBE at a growth rate of 0.1 ML/s at 480°C on an n-type GaAs͑001͒ substrate after deposition of an n-type GaAs buffer layer ͑Si: 1 ϫ 10 18 cm −2 ͒. The formation of the GaSb quantum dots was detected by the change in the reflection high energy electron diffraction ͑RHEED͒ pattern after deposition of 1.8 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 an additional 20 s. 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 quantum dot nucleation. In the second one, a 40 nm thick GaAs layer was deposited at 570°C. During the growth, the As and Sb beam equiv...

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“…As revealed in the figure, similar PL and EL spectra curves with two peaks 1.09 and 1.20 eV are observed, which suggests that the same transition mechanisms are responsible for the two spectra. In previous publications, the PL spectra of the GaSb QDs are mostly observed at low temperature [5,6]. One possible mechanism responsible for this phenomenon may be the dislocations produced in the Sb/As interfaces such that only luminescence at low temperature could be observed.…”

Section: Resultsmentioning

confidence: 94%

“…The choice of different barriers may provide even longer emitting wavelengths for the devices based on this QD structure. In previous reports, despite its type-II alignment, photoluminescence (PL) are already observed for GaSb/GaAs QDs [5,6]. A light-emitting diode (LED) based on the type-II GaSb/GaAs QD structure operated at room temperature has also been demonstrated elsewhere [7].…”

Section: Introductionmentioning

confidence: 97%