Observation of change in critical thickness of In droplet formation on GaAs(100)

Lee, Jihoon; Wang, Zh. M.; Salamo, Gregory J.

doi:10.1088/0953-8984/19/17/176223

Cited by 33 publications

(48 citation statements)

References 26 publications

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“…With a further increase of ML deposition to 20, the average density was slightly decreased to 3.68 × 10 10 cm −2 on the trench area and to 3.9 × 10 9 cm −2 on strip area. In previous experiments, an increase of the average MD density was observed when ML deposition was increased [36,37]. Also, slightly reduced density was observed depending on the growth conditions, i.e., duration, G rate , and T sub .…”

Section: Resultsmentioning

confidence: 72%

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Formation of Ga droplets on patterned GaAs (100) by molecular beam epitaxy

Hirono

Koukourinkova

et al. 2012

Nanoscale Res Lett

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In this paper, the formation of Ga droplets on photo-lithographically patterned GaAs (100) and the control of the size and density of Ga droplets by droplet epitaxy using molecular beam epitaxy are demonstrated. In extension of our previous result from the journal Physical Status Solidi A, volume 209 in 2012, the sharp contrast of the size and density of Ga droplets is clearly observed by high-resolution scanning electron microscope, atomic force microscope, and energy dispersive X-ray spectrometry. Also, additional monolayer (ML) coverage is added to strength the result. The density of droplets is an order of magnitude higher on the trench area (etched area), while the size of droplets is much larger on the strip top area (un-etched area). A systematic variation of ML coverage results in an establishment of the control of size and density of Ga droplets. The cross-sectional line profile analysis and root mean square roughness analysis show that the trench area (etched area) is approximately six times rougher. The atomic surface roughness is suggested to be the main cause of the sharp contrast of the size and density of Ga droplets and is discussed in terms of surface diffusion.

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Section: Resultsmentioning

confidence: 72%

“…The control of droplets on planar substrates has been somewhat widely studied [9-23,36,37]; however, the fabrication of MDs on patterned surfaces lacks its investigation. This very naturally puts the control of MDs on patterned substrate as an attractive and essential research topic.…”

Section: Introductionmentioning

confidence: 99%

Formation of Ga droplets on patterned GaAs (100) by molecular beam epitaxy

Hirono

Koukourinkova

et al. 2012

Nanoscale Res Lett

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“…This dimension was suitable for hosting a single QDM per each droplet. In addition, the size and the density of In droplets can be controlled by modifying T sub , deposition amount, and in-situ annealing [38], [39], and thus, the density and size would easily be controlled depending on the necessity. The next step to achieve low density of QDMs was to remove the QDMs that are out of the In droplets.…”

Section: Resultsmentioning

confidence: 99%

Low-Density Quantum Dot Molecules by Selective Etching Using in Droplet as a Mask

Lee¹,

Wang²,

Hirono³

et al. 2011

IEEE Trans. Nanotechnology

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We demonstrate low-density quantum dot molecules (QDMs) by selective etching using In droplets as a mask. Selective etching is performed with InGaAs QDMs buried underneath GaAs capping layer, on which In droplets are formed by droplet epitaxy using molecular beam epitaxy. During the chemical etching, the droplets act as a mask and QDMs underneath the droplets that only survive. Photoluminescence measurement from the selectively etched QDMs in mesa structures shows a much reduced intensity, which indicates low-density QDMs. This technique provides a simple and flexible method to attain low-density QDMs. The density can be easily modified by the control of the size and density of In droplets, which is suitable for single QDM spectroscopy and for their device applications.Index Terms-Atomic force microscopy (AFM), droplets, low density, molecular beam epitaxy (MBE), photoluminescence (PL), quantum dot molecules (QDMs), selective etching.

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“…These droplets act as nucleation centers to capture the supplied As atoms and surrounding In atoms resulting into 3D InAs structures when the As cell is open. 16,17 Therefore, InAs QDs would start forming from the onset of the InAs deposition as observed by RHEED. In fact, 18 This result is not in contradiction with the random nucleation of small metallic droplets, 19 which can migrate toward favorable sites during their crystallization into semiconductor nanostructures.…”

mentioning

confidence: 92%

Direct formation of InAs quantum dots grown on InP (001) by solid-source molecular beam epitaxy

Fuster¹,

Rivera²,

Alén³

et al. 2009

Applied Physics Letters

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We have developed a growth process that leads to the direct formation of self-assembled InAs quantum dots on InP͑001͒ by solid-source molecular beam epitaxy avoiding the previous formation of quantum wires usually obtained by this technique. The process consists of a periodically alternated deposition of In and As correlated with InAs͑4 ϫ 2͒ ↔ ͑2 ϫ 4͒ surface reconstruction changes. Based on the results obtained by in situ characterization techniques, we propose that the quantum dots formation is possible due to the nucleation of In droplets over the InAs͑4 ϫ 2͒ surface during the In deposition step and their subsequent crystallization under the As step. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3108087͔ Semiconductor self-assembled quantum dots ͑QDs͒ have received much attention because of their application in advanced optical devices. 1,2 In particular, the active elements based on the InAs/InP heteroepitaxial system are interesting for their use in laser devices emitting at 1.55 m, compatible with optical fiber communications. 3 The self-assembling of QDs is a strain-driven process that takes place in highly lattice-mismatched semiconductor materials. The strained material grows in a layer-by-layer mode up to a certain critical thickness and then the growth mode switches from two dimensional ͑2D͒ to three dimensional ͑3D͒ with the net result of elastic energy relaxation ͑Stranski-Krastanov process͒. The InAs/GaAs heteroepitaxial system is a well studied example of this kind of process. 4 However, in the InAs/ InP͑001͒ heteroepitaxial system growing under usual molecular beam epitaxy ͑MBE͒ conditions, quantum wires ͑QWRs͒ elongated along the ͓110͔ direction are formed instead of QDs, which are in principle more efficient for elastic energy relaxation. Other authors have recently recognized the key role of the InAs As-rich ͑2 ϫ 4͒ surface reconstruction in a growth model for QWR formation. 5 Other works report the InAs/InP͑001͒ QD formation using MBE but always through the evolution of previously formed QWRs: either by the ripening of the initial QWRs during substrate cooling down under arsenic overpressure 6 or after substrate annealing under no arsenic flux at the InAs͑4 ϫ 2͒ surface reconstruction. 7 In a previous model we proposed that the growth of InAs on InP under a ͑2 ϫ 4͒ V element ended surface reconstruction produces a stress asymmetry at the InAs/InP interface, inducing an asymmetric relaxation process that finally results in QWR formation. 8,9 According to our previous model, the built-in interface strain anisotropy could be inhibited if the surface would be terminated in III element. 9 Therefore, if those conditions could be experimentally achieved, for example, growing InAs on the In-rich ͑4 ϫ 2͒ surface reconstruction, QDs instead of QWRs would be directly obtained in the InAs/InP͑001͒ system.In this work we have developed a method to implement this idea. The method consists of depositing InAs in a pulsed mode under experimental conditions in which the surface shows most of the growt...

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Observation of change in critical thickness of In droplet formation on GaAs(100)

Cited by 33 publications

References 26 publications

Formation of Ga droplets on patterned GaAs (100) by molecular beam epitaxy

Formation of Ga droplets on patterned GaAs (100) by molecular beam epitaxy

Low-Density Quantum Dot Molecules by Selective Etching Using in Droplet as a Mask

Direct formation of InAs quantum dots grown on InP (001) by solid-source molecular beam epitaxy

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