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

Ulloa, J. M.; Llorens, Jorge Cardona; Alén, Benito; Reyes, Daniel; Sales, D.; González, David; Hierro, A.

doi:10.1063/1.4773008

Cited by 26 publications

(34 citation statements)

References 23 publications

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“…Previous results had shown that the incorporation of a high Sb content in the SRL extended the emission wavelength of InAs QDs to 1345 nm (at 15 K) and induced a type II band alignment, as revealed by the large radiative lifetime of 14.2 ns (further details of PL and time-resolved PL of these samples can be found in [19]). More important, the RTA retained the type II emission (radiative lifetime of 11.8 ns) while producing a significant enhancement of the PL, increasing both the integrated intensity (by a factor of 3.3) and monochromaticity (FWHM reduced from 97 meV to 32 meV, i.e., by 67%).…”

Section: Resultsmentioning

confidence: 99%

“…In these images, the wetting layer (WL) and QDs can be clearly distinguished with a darker contrast than GaAs, while the capping layer exhibits a brighter contrast. Our measurement on more than 60 QDs [19] showed that the RTA gave way to an important reduction of the average height (from 3.3 ±0.6 to 2.3±0.4nm) together to an increase of the base diameter (from 16±4nm to 22±7nm). In addition, the thickness of the SRL was reduced by approximately 1 nm, i.e., from 6.5 to 5.5 nm in areas far from the QDs.…”

Section: Ctem Analysesmentioning

confidence: 98%

“…These clusters, which must have possibly formed by the aggregation of Sb and In from the CL and WL, respectively, have a lattice mismatch with the matrix up to 10% that would explain the formation of the dislocation loops for strain relief. Surprisingly, the formation of Sb-rich clusters in conjunction with dislocation loops does not impair the PL intensity (actually, the peak intensity increases 10 times [19]). …”

Section: Ctem Analysesmentioning

confidence: 99%

“…An alternative approach to control the Sb distribution is the use of postgrowth thermal annealing that can be used to tailor the band alignment, the wave function overlaps, and hence the recombination dynamics in the InAs/GaAsSb type II QDs [18]. Recently, we have reported about the effect of rapid thermal annealing (RTA) on this kind of sample where large blueshifts and a strong enhancement of emission efficiency were observed while preserving the long radiative lifetimes [19]. However, there was a lack of knowledge about the processes involved during annealing.…”

Section: Introductionmentioning

confidence: 99%

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Effect of annealing in the Sb and In distribution of type II GaAsSb-capped InAs quantum dots

Reyes

Ulloa

Guzmán

et al. 2015

Semicond. Sci. Technol.

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Type II emission optoelectronic devices using GaAsSb strain reduction layers (SRL) over InAs quantum dots (QDs) have aroused great interest. Recent studies have demonstrated an extraordinary increase in photoluminescence (PL) intensity maintaining type II emission after a rapid thermal anneal (RTA), but with an undesirable blueshift. In this work, we have characterized the effect of RTA on InAs/GaAs QDs embedded in a SRL of GaAsSb by transmission electron microscopy (TEM) and finite element simulations. We find that annealing alters both the distribution of Sb in the SRL as well as the exchange of cations (In and Ga) between the QDs and the SRL. First, annealing causes modifications in the capping layer, reducing its thickness but maintaining the maximum Sb content and improving its homogeneity. In addition, the formation of Sb-rich clusters with loop dislocations is noticed, which seems not to be an impediment for an increased PL intensity. Second, RTA produces flatter QDs with larger base diameter and induces a more homogeneous QD height distribution. The Sb is accumulated over the QDs and the RTA enlarges the Sb-rich region, but the Sb contents are very similar. This fact leaves the type II alignment without major changes. Atomic-scale strain analysis of the nanostructures reveal a strong intermixing of In/Ga between the QDs and the capping layer, which is the main responsible mechanism of the PL blueshift. The improvement of the crystalline quality of the capping layer together with higher homogeneity QD sizes could be the origin of the enhancement of the PL emission.

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Section: Resultsmentioning

confidence: 99%

Section: Ctem Analysesmentioning

confidence: 98%

Section: Ctem Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of annealing in the Sb and In distribution of type II GaAsSb-capped InAs quantum dots

Reyes

Ulloa

Guzmán

et al. 2015

Semicond. Sci. Technol.

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“…14 Rapid thermal annealing of these samples resulted in type-II QDs with highly efficient luminescence which are, nevertheless, not optimal candidates as laser gain material due to the type-II alignment. 15 The Sb incorporation method on the InAs nanostructures plays a crucial role in InAsSb QDs' great performance for optical applications. Previous papers reporting on the optical characterization of InAsSb QDs directly grown on GaAs addressed that, independent of the Sb beam flux used during growth, the emission was blueshifted with respect to the InAs QD reference ensembles (blueshift ranging from 42 to 106 meV).…”

Section: Introductionmentioning

confidence: 99%

Effect of Sb incorporation on the electronic structure of InAs quantum dots

Taboada¹,

Llorens²,

Alonso-Álvarez³

et al. 2013

Phys. Rev. B

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On the basis of optical characterization experiments and an eight band kp model, we have studied the effect of Sb incorporation on the electronic structure of InAs quantum dots (QDs). We have found that Sb incorporation in InAs QDs shifts the hole wave function to the center of the QD from the edges of the QD where it is otherwise pinned down by the effects of shear stress. The observed changes in the ground-state energy cannot merely be explained by a composition change upon Sb exposure but can be accounted for when the change in lateral size is taken into consideration. The Sb distribution inside the QDs produces distinctive changes in the density of states, particularly, in the separation between excitation shells. We find a 50% increase in the thermal escape activation energy compared with reference InAs quantum dots as well as an increment of the fundamental transition decay time with Sb incorporation. Furthermore, we find that Sb incorporation into quantum dots is strongly nonlinear with coverage, saturating at low doses. This suggests the existence of a solubility limit of the Sb incorporation into the quantum dots during growth.

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Capping vertically aligned InGaAs/GaAs(Sb) quantum dots with a AlGaAsSb spacer layer in intermediate‐band solar cell devices

Liu

Lin

Liu

2016

Progress in Photovoltaics

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This study demonstrated the feasibility of fabricating a highly stacked vertically aligned InGaAs/GaAs(Sb) quantum dot (QD) structure with an AlGaAsSb spacer layer for improving the device performance of QD intermediate-band solar cell (QD-IBSC) devices. The power-dependent photoluminescence measurements of the proposed structure revealed a blueshift in the QD ground-state emissions when the excitation power was increased, indicating the formation of an intermediate band inside the QD structure. Capping the InGaAs QDs with a GaAsSb layer prevented the QDs from collapsing because there was less In-Ga intermixing between the QDs and GaAsSb layer. In addition to maintaining the QD structure, the carrier lifetime was extended by tuning the energy band alignment of the InGaAs/GaAsSb QD structure. Inserting the AlGaAsSb layer into the spacer layer increased the band gap, which in turn increased the open-circuit voltage of the QD-IBSC. The QD-IBSC in this work shows an extension of external-quantum efficiency by up to 1200 nm (compared with a GaAs reference cell) through the absorption by QDs and increased the open-circuit voltage from 0.67 to 0.70 V by adopting the AlGaAsSb spacer layer. These results confirm that adopting a columnar InGaAs/GaAs(Sb) QD structure with a AlGaAsSb spacer layer can enhance the performance of QD-IBSC devices.

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

Cited by 26 publications

References 23 publications

Effect of annealing in the Sb and In distribution of type II GaAsSb-capped InAs quantum dots

Effect of annealing in the Sb and In distribution of type II GaAsSb-capped InAs quantum dots

Effect of Sb incorporation on the electronic structure of InAs quantum dots

Capping vertically aligned InGaAs/GaAs(Sb) quantum dots with a AlGaAsSb spacer layer in intermediate‐band solar cell devices

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