Morphology Of Quantum Dots Research Articles

Ripening suppression and large photoluminescence blueshift in aligned InGaAs quantum dots on a vicinal (100) GaAs substrate

We observe ripening suppression in aligned InGaAs quantum dots (QDs) along multiatomic steps on a vicinal (100) GaAs substrate. By varying the growth interruption times, a study of QD morphologies by atomic force microscope reveals a clear Ostwald ripening suppression effect on QD formation. On the other hand, we observe a regular ripening for InGaAs QDs on an exact (100) substrate. In addition, n-QD chains aligned along multiatomic steps are observed. An inhomogeneously broadened photoluminescence (PL) spectrum with larger spectral width is obtained for a QD ensemble on a vicinal (100) substrate as compared to those on an exact (100) substrate although statistical analyses of QD size distributions show similar size dispersions. The spectral broadening is attributed to the lateral quantum coupling of aligned n-QD chains. PL spectra for QDs on vicinal (100) substrates show a larger rate of blueshift with increasing interruption times, which is interpreted as a lack of the PL compensation effect by size enlargement of the QDs during growth interruption. Thus the result supports the ripening suppression effect which is observed in the morphology study.

Self-Assembled Iii-Phospide Quantum Dots Grown by Metalorganic Chemical Vapor Deposition

AbstractWe report InP self-assembled quantum dots embedded in In0.51Al0.49P grown by metalorganic chemical vapor deposition. Growth parameters are altered to study the InP quantum-dot growth characteristics under various growth conditions. Quantum-dot morphology is characterized using atomic-force microscopy. Also, photoluminescence studies of the light-emitting properties are performed. Direct-bandgap ternary InxAlI−xP (x=˜0.7, ˜0.85) self-assembled quantum dots are also grown and compared with InP quantum dots.

MORPHOLOGY AND PHOTOLUMINESCENCE OF GeSi SELF-ASSEMBLED QUANTUM DOT ON Si(113)

Morphology of self-assembled GeSi quantum dot grown on Si(113) by Si molecular beam epitaxy has been studied by transmission electron microscopy and atomic force microscopy.Photoluminescence from the as-grown sample and annealed sample was studied.The res

Tem Investigation of Self-Organized Pbse Quantum Dots as a Function of Spacer Layer Thickness and Growth Temperature

AbstractThe study of the morphology, lateral and vertical correlation of self-organized PbSe quantum dots in Pb1−xEux Te is presented. The samples consist of quantum dot superlattices of n periods of (PbSe/Pb1−xEux Te) grown on PbTe/(111) BaF2 by the S-K mode using MBE. The Pb1−xEux Te spacer thickness was varied from 34.3nm to 312nm and the growth temperature was varied between 335°C and 380°C. Our TEM results show very good lateral and vertical correlation of the dots. The dots form an array with either a/b/c/a/b/c/... or a/a/a/... vertical stacking sequence along the [111] growth direction. The stacking sequence is accurately controlled by the thickness of the Pb1−xEux Te spacer layer thickness and the growth temperature. The best a/b/c/... spatial correlation was obtained for temperatures around 380°C and spacer thickness of ˜40nm. The dots are highly strained and form triangular pyramids with (111) bases and (100) facets as observed by AFM. The shape of the dots also varied with the Pb1−xEux Te spacer thickness. An analysis of the spatial correlation of the dots' size and shape with respect to spacer thickness and growth temperature is presented.

Transmission-electron microscopy study of the shape of buriedInxGa1−xAs/GaAsquantum dots

High-resolution electron microscopy, on-zone bright-field imaging, and image simulation were used to investigate the shape of capped ${\mathrm{In}}_{0.6}{\mathrm{Ga}}_{0.4}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ semiconductor quantum dots. Cross-section 〈110〉 high-resolution images suggest that the quantum dots are lens shaped, while the [001] on-zone bright-field images show a contrast that suggests a quantum dot morphology with four edges parallel to 〈100〉. The image simulation, however, suggests that a spherical quantum dot can produce a square-shaped image. These observations lead to the conclusion that the quantum dots in buried ${\mathrm{In}}_{0.6}{\mathrm{Ga}}_{0.4}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ semiconductor heterostructures are lens shaped.

Comparison between AS-Grown and Annealed Quantum Dots Morphology

Comparison between AS-Grown and Annealed Quantum Dots Morphology

In-mole-fraction of InGaAs Insertion Layers Effects on the Structural and Optical Properties of GaSb Quantum Dots Grown on (001) GaAs Substrate

GaSb quantum dots (QDs) have been grown by solid-source molecular beam epitaxy on a 4-monolayer (ML) InxGa1-xAs (x = 0.07, 0.15, 0.20, and 0.25) to investigate the effects of In-mole-fraction of InGaAs insertion layers on the structural and optical properties of the GaSb QDs. The density of grown GaSb QDs is approximately 1.2-2.8109 cm−2 on In-GaAs insertion layers which depends on the In-molefraction. Dot shape and size change substantially when In-mole-fraction of InGaAs insertion layers is varied. The uniformity of GaSb QDs improves when the indium content increases. The change in freestanding QD morphology is likely due to the modified strain at different values of indium compositions in InGaAs insertion layers. The effects of In-molefraction of InGaAs insertion layer on optical properties of the QDs are studied by photoluminescence (PL). PL results show the blueshift of the emission when the indium content in InGaAs insertion layer increases.