Key parameters for the formation of II–VI self-assembled quantum dots

Tinjod, F.; Robin, I. C.; André, R.; Kheng, K.; Mariette, H.

doi:10.1016/j.jallcom.2003.05.006

Cited by 41 publications

(37 citation statements)

References 20 publications

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“…This is confirmed by the observation in situ of a streaky RHEED pattern as previously reported for CdTe/ZnTe (see for example Cibert et al [8]). Note that this behavior contrasts with the one predicted [17] and observed [18] for InAs/GaAs (001): in this case the transition which occurs first is the elastic one with the formation of coherent islands at a critical thickness h c SK of about 1.7 ML. The different behavior between the two types of systems, II-VIs as compared to III-Vs, is mainly due to the lower values of E MD for the former ones.…”

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confidence: 81%

Self‐assembled quantum dot formation induced by surface energy change of a strained two‐dimensional layer

Tinjod

Mariette

2004

Physica Status Solidi (b)

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To account for the occurrence (or not) of the Stranski-Krastanow (SK) transition (two-dimensional to 3D change of surface morphology) during the epitaxial growth of various lattice-mismatched semiconductor systems, we present a simple equilibrium model taking into account not only the lattice mismatch, but also the dislocation formation energy and the surface energy. It demonstrates the importance of these parameters especially for II-VI systems such as CdTe/ZnTe and CdSe/ZnSe. For II-VIs indeed, as misfit dislocations are easier to form than in III-Vs (such as InAs/GaAs) or IV systems (Ge/Si), the 3D elastic transition is short-circuited by the plastic one. Nevertheless, by lowering surface energy, telluride and selenide quantum dots can also be grown as predicted by our model and as evidenced experimentally by reflection high-energy electron diffraction (RHEED), atomic force microscopy and optical measurements.1 Introduction Some combinations of lattice-mismatched semiconductors can exhibit, under specific epitaxial growth conditions, a sharp transition from a layer-by-layer 2D growth to the formation of 3D islands. This Stranski-Krastanow (SK) growth mode [1] allows the relaxation of highly strained 2D layers trough the strain-free facets of 3D islands instead of generating misfit dislocations (MD) [2]. These islands are expected to be dislocation-free and are thus of high structural quality. Usually their typical sizes are on the scale of a few nanometers, so that these self-assembled quantum dots (QDs) are attractive nanostructures for the study of zero dimensional effects.The formation, above a critical film thickness, of such QDs by molecular beam epitaxy (MBE) is now well established for III-V semiconductors such as InAs/GaAs [3]. The large lattice mismatch (∆a/a ≈ 7%) between these two semiconductors is seen as the driving force which induces the 2D-3D change of the surface morphology with the formation of SK islands. However, in the case of II-VI systems, which can exhibit mismatch as large as 6% for CdTe/ZnTe or CdSe/ZnSe, the 2D-3D transition is much less obvious: no clear 3D RHEED pattern has been reported during growth although zero-dimensional behavior was obtained [4][5][6][7]. In II-VIs indeed, above critical thickness, MD form easier than in III-Vs as clearly observed for CdTe/ZnTe by Cibert et al. [8], which corresponds to a plastic relaxation as first considered by Frank and van der Merwe [2]. On the other hand, there are systems such as GaN/AlN [9] or SiGe/Si [10,11], with lower misfit (respectively 2.4% and less than 4%), which are known for exhibiting a clear SK transition with the formation of coherent islands.There are therefore other parameters than the lattice mismatch in order to account for the 2D-3D transition. In this paper a simple equilibrium model taking into account not only the lattice mismatch but also the dislocation formation energy and the surface energy, is presented to explain the occurrence (or not) of this 2D-3D transition for various semiconductor systems.

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confidence: 81%

Self‐assembled quantum dot formation induced by surface energy change of a strained two‐dimensional layer

Tinjod

Mariette

2004

Physica Status Solidi (b)

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“…After the CdTe buffer, a 1 µm thick ZnTe barrier layer is grown. The quantum dots are formed by deposition of 6 monolayers of CdTe which are covered with an amorphous tellurium layer at a low substrate temperature [6,7]. After thermal desorption of the Te layer at 350…”

Section: Methodsmentioning

confidence: 99%

“…QDs based on III-V semiconductors are studied more intensively in comparison with their counterparts based on II-VI material systems, due to some difficulties in the fabrication of the latter structures. In CdTe/ZnTe material system, the QD formation does not take place spontaneously despite a similar lattice mismatch as in commonly used InAs/GaAs system, but it is usually induced by an additional procedure such as exposing a thin strained CdTe/ZnTe quantum well structure to a Cd flux at an enhanced substrate temperature [4,5], or covering it with amorphous tellurium (283) at a low substrate temperature and its subsequent desorption [6,7]. The main advantage of the latter method is the possibility of in situ observation of the QDs formation by means of reflection of high energy electron diffraction (RHEED), similarly as for III-V compounds.…”

Section: Introductionmentioning

confidence: 99%

Changing the Properties of the CdTe/ZnTe Quantum Dots by in situ Annealing during the Growth

et al. 2007

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We present an attempt to control the properties of CdTe/ZnTe self--assembled quantum dots during their formation in the process of molecular beam epitaxy. Namely, the structures were in situ annealed at various temperatures and annealing times after the formation of quantum dots, before the deposition of a capping layer. Depending on the annealing parameters, the dots exhibit different optical properties which were studied by means of spatially resolved photoluminescence. From the analysis of these results, the information about relative changes of the average size and sheet density of quantum dots was extracted.

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“…Zn 1−x Cd x Se/ZnSe band osets were determined based on a model-solid theory [12], taking account of ≈ 40% elastic stress accommodation that occurs during CdSe QDs formation [13]. Results of the luminescence wavelength calculation at 300 K as a function of the surrounding ZnCdSe QW width (t QW )…”

Section: Theoretical Calculationsmentioning

confidence: 99%

CdSe/ZnCdSe Quantum Dot Heterostructures for Yellow Spectral Range Grown on GaAs Substrates by Molecular Beam Epitaxy

Gronin¹,

Sorokin²,

Kazanov

et al. 2014

Acta Phys. Pol. A

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This paper reports on theoretical calculations and fabrication by molecular beam epitaxy of wide-gap IIVI heterostructures emitting in the true yellow range (560600 nm) at room temperature. The active region of the structures comprises CdSe quantum dot active layer embedded into a strained Zn1−xCdxSe (x = 0.2−0.5) quantum well surrounded by a Zn(S,Se)/ZnSe superlattice. Calculations of the CdSe/(Zn,Cd)Se/Zn(S,Se) quantum dot quantum well luminescence wavelength performed using the envelope-function approximation predict rather narrow range of the total Zn1−xCdxSe quantum well thicknesses (d ≈ 2−4 nm) reducing eciently the emission wavelength, while the variation of x (0.20.5) has much stronger eect. The calculations are in a reasonable agreement with the experimental data obtained on a series of test heterostructures. The maximum experimentally achieved emission wavelength at 300 K is as high as 600 nm, while the intense room temperature photoluminescence has been observed up to λ = 590 nm only. To keep the structure pseudomorphic to GaAs as a whole the tensile-strained surrounding ZnS0.17Se0.83/ZnSe superlattice were introduced to compensate the compressive stress induced by the Zn1−xCdxSe quantum well. The graded-index waveguide laser heterostructure with a CdSe/Zn0.65Cd0.35Se/Zn(S,Se) quantum dotquantum well active region emitting at λ = 576 nm (T = 300 K) with the 77 to 300 K intensity ratio of 2.5 has been demonstrated.

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Key parameters for the formation of II–VI self-assembled quantum dots

Cited by 41 publications

References 20 publications

Self‐assembled quantum dot formation induced by surface energy change of a strained two‐dimensional layer

Self‐assembled quantum dot formation induced by surface energy change of a strained two‐dimensional layer

Changing the Properties of the CdTe/ZnTe Quantum Dots by in situ Annealing during the Growth

CdSe/ZnCdSe Quantum Dot Heterostructures for Yellow Spectral Range Grown on GaAs Substrates by Molecular Beam Epitaxy

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