Articles de revues : « InAs QDs on silicon »

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Abouzaid, Oumaima, Hussein Mehdi, Mickael Martin, Jérémy Moeyaert, Bassem Salem, Sylvain David, Abdelkader Souifi et al. « O-Band Emitting InAs Quantum Dots Grown by MOCVD on a 300 mm Ge-Buffered Si (001) Substrate ». Nanomaterials 10, n^o 12 (7 décembre 2020) : 2450. http://dx.doi.org/10.3390/nano10122450.

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The epitaxy of III-V semiconductors on silicon substrates remains challenging because of lattice parameter and material polarity differences. In this work, we report on the Metal Organic Chemical Vapor Deposition (MOCVD) and characterization of InAs/GaAs Quantum Dots (QDs) epitaxially grown on quasi-nominal 300 mm Ge/Si(001) and GaAs(001) substrates. QD properties were studied by Atomic Force Microscopy (AFM) and Photoluminescence (PL) spectroscopy. A wafer level µPL mapping of the entire 300 mm Ge/Si substrate shows the homogeneity of the three-stacked InAs QDs emitting at 1.30 ± 0.04 µm at room temperature. The correlation between PL spectroscopy and numerical modeling revealed, in accordance with transmission electron microscopy images, that buried QDs had a truncated pyramidal shape with base sides and heights around 29 and 4 nm, respectively. InAs QDs on Ge/Si substrate had the same shape as QDs on GaAs substrates, with a slightly increased size and reduced luminescence intensity. Our results suggest that 1.3 μm emitting InAs QDs quantum dots can be successfully grown on CMOS compatible Ge/Si substrates.

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Li, Yuan-He, Zhi-Yao Zhuo, Jian Wang, Jun-Hui Huang, Shu-Lun Li, Hai-Qiao Ni, Zhi-Chuan Niu, Xiu-Ming Dou et Bao-Quan Sun. « Controlling exciton spontaneous emission of quantum dots by Au nanoparticles ». Acta Physica Sinica 71, n^o 6 (2022) : 067804. http://dx.doi.org/10.7498/aps.71.20211863.

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As an ideal single-photon source, quantum dots (QDs) can play a unique role in the field of quantum information. Controlling QD exciton spontaneous emission can be achieved by anti-phase coupling between QD exciton dipole field and Au dipole field after QD film has been transferred onto the Si substrate covered by Au nanoparticles. In experiment, the studied InAs/GaAs QDs are grown by molecular beam epitaxy (MBE) on a (001) semi-insulation substrate. The films containing QDs with different GaAs thickness values are separated from the GaAs substrate by etching away the AlAs sacrificial layer and transferring the QD film to the silicon wafer covered by Au nanoparticles with a diameter of 50 nm. The distance D (thickness of GaAs) from the surface of the Au nanoparticles to the QD layer is 10, 15, 19, 25, and 35 nm, separately. A 640-nm pulsed semiconductor laser with a 40-ps pulse length is used to excite the QD samples for measuring QD exciton photoluminescence and time-resolved photoluminescence spectra at 5 K. It is found that when the distance D is 15–35 nm the spontaneous emission rate of exciton is suppressed. And when D is close to 19 nm, the QD spontaneous emission rate decreases to <inline-formula><tex-math id="M2">\begin{document}$ ~{10}^{-3} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211863_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211863_M2.png"/></alternatives></inline-formula>, which is consistent with the theoretical calculations. The physical mechanism of long-lived exciton luminescence observed in experiment lies in the fact that Au nanoparticles scatter the light field of the exciton radiation in the QD wetting layer, and the phase of the scattered field is opposite to the phase of the exciton radiation field. Therefore, the destructive interference between the exciton radiation field and scattering field of Au nanoparticles results in long-lived exciton emission observed in experiment.

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Yamamoto, N., K. Akahane, S. Gozu et Noboru Ohtani. « Growth of InAs Quantum Dots on a Low Lattice-Mismatched AlGaSb Layer Prepared on GaAs (001) Substrates ». Solid State Phenomena 99-100 (juillet 2004) : 49–54. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.49.

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Optical communication wavelength emissions from the quantum dots (QDs) structures prepared on (001)-oriented GaAs substrates are discussed. A new growth technique of low-stressed InAs QDs on the AlGaSb layer in a low lattice-mismatched (1.3%) InAs/AlGaSb system is presented. The average height and diameter of the 4-ML InAs QDs on AlGaSb are evaluated to 5.8 nm and 45.2 nm respectively with an average density of 2.18 x 1010 /cm2 using atomic force microscope (AFM) measurements. There is structural selectivity between the QDs layer and the flat hetero-interface under changing growth conditions in the InAs/AlGaSb system. Long-wavelength PL emissions around 1.3 µm and 1.55 µm can be achieved by embedding InAs QDs in AlGaSb layers. Therefore it is expected that low-stressed InAs QDs grown on a AlGaSb layer prepared on a GaAs substrate will be useful in the fabrication of novel QDs devices for optical-communication networks.

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Saravanan, S. « Stacking of InAs QDs with Different Spacer Layer Thickness on GaAs Substrate by Molecular Beam Epitaxy ». Advanced Science Letters 24, n^o 8 (1 août 2018) : 5574–77. http://dx.doi.org/10.1166/asl.2018.12152.

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InAs QDs were grown by supplying 2.5 mono-layers (MLs) of InAs at 500 °C in a molecular beam epitaxial (MBE) system. The QDs are approximately 4–6 nm height with an areal density of 3×85 ×1010 cm−2 for single layer QDs. Typical diameter was found to be about 15–25 nm. InAs QDs were stacked with the spacer layer thickness of 5, 10, 15, 25 and 35 nm. For 15 nm of spacer layer thickness the QDs density decreased to 2.62×1010 cm−2 and again increased for 35 nm spacer layer and reached to the value of 3.65×1010 cm−2. The 14 K photoluminescence (PL) spectra of single layer InAs QDs covered by GaAs layer centered at 1079 nm. For the stacking of InAs QDs with spacer layer thickness of 5 and 10 nm another peak appeared around 1100 nm due to size broadening of QDs because of strain propagation to next layer due to less thickness of spacer layer. When the thickness of the spacer layer increased to 35 nm the peak position is around 1073 nm and the intensity increased more than 3 fold when compare to single layer QDs.

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Yao, Jian Ming, Ling Min Kong et Shi Lai Wang. « Effects of a InGaAs Strained Layer on Structures and Photoluminescence Characteristics of InAs Quantum Dots ». Advanced Materials Research 148-149 (octobre 2010) : 897–902. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.897.

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The influences of a thin InGaAs layer grown on GaAs(100) substrate before deposited InAs self-assembled quantum dots(SAQDs) were experimentally investigated. Scanning electronic microscope (SEM) measurements show that the InGaAs strained layer may release the strain between wetting layer and QDs, and then enlarge size of QDs. When the thickness of InAs layer is small, the QDs are chained. Temperature dependent photoluminescence (TDPL) measurements show that the PL peaks of InAs QDs with In0.1Ga0.9As show much more red shift compared with the QDs directly deposited on GaAs matrix, and PL integral intensity enhances as T rises from 50K to 90K. We attribute this enhancement to the small potential barrier between WL and QDs produced by the InGaAs stained layer.

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Mehta, M., D. Reuter, M. Kamruddin, A. K. Tyagi et A. D. Wieck. « Influence of Post-Implantation Annealing Parameters on the Focused Ion Beam Directed Nucleation of InAs Quantum Dots ». Nano 10, n^o 04 (juin 2015) : 1550049. http://dx.doi.org/10.1142/s1793292015500496.

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We present the effect of post-implantation annealing conditions on the structural and optical quality of InAs quantum dots (QDs) grown by combination of focused ion beam (FIB) and molecular beam epitaxy (MBE) approach. A FIB of Ga + ion was employed to pattern a homogeneously GaAs buffer layers and then, an in situ annealing step followed by InAs deposition was performed. Three different post-implantation annealing conditions were tested and under well-optimized conditions, a dislocation and defect-free InAs QDs growth on FIB patterned surface was successfully achieved. Furthermore, using photoluminescence (PL) study, we demonstrate that our best sample shows almost similar optical quality as MBE grown QDs on unimplanted GaAs surface. The patterning technique described here can presumably be applied to systems other than InAs / GaAs and highly interesting for site-controlled nucleation of QDs that finds its potential applications in nanooptoelectronic devices.

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Volkova, N. S., A. P. Gorshkov, L. A. Istomin, A. V. Zdoroveyshchev et S. Levichev. « Diagnostic of the Bimodal Distribution of InAs/GaAs Quantum Dots by Means of a Simple Nondestructive Method Based on the Photoelectrical Spectroscopy ». Nano 11, n^o 10 (29 septembre 2016) : 1650109. http://dx.doi.org/10.1142/s1793292016501095.

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Photoelectric spectra of heterostructures containing InAs quantum dots (QDs) produced in different technological regimes were studied. A simple nondestructive method to reveal a bimodality of the QDs’ size distribution was described. The method based on the analysis of the shape of InAs/GaAs QDs’ photoelectric spectra and their temperature dependencies. The quantitative analysis of the temperature dependencies of the photoelectrical spectra was performed. All possible emission processes occurring from quantum confined levels to the semiconductor matrix were considered at the simulation. The surface concentration of the QDs was estimated.

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Schramboeck, M., A. M. Andrews, P. Klang, W. Schrenk, G. Hesser, F. Schäffler et G. Strasser. « InAs/AlGaAs QDs for intersubband devices ». Superlattices and Microstructures 44, n^o 4-5 (octobre 2008) : 411–15. http://dx.doi.org/10.1016/j.spmi.2007.10.010.

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Kim, Eui Tae, et Anupam Madhukar. « Growth Kinetics and Formation of Uniform Self-Assembled InAs/GaAs Quantum Dots at ». Solid State Phenomena 124-126 (juin 2007) : 539–42. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.539.

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We discuss the growth kinetics of InAs/GaAs self-assembled quantum dots (QDs) using two different InAs deposition rates, relatively fast growth rate of 0.22 ML/sec and slow growth rate of 0.054 ML/sec. With increasing InAs deposition amount to 3.0 ML, the QD density was almost constant after 2D to 3D island transition at the slow deposition rate while the QD density kept increasing and the QD size distribution was relatively broad at the fast growth rate. After the 2D to 3D transition, at the slow growth rate, further deposited In adatoms seemed to incorporate primarily into already formed islands, and thus contribute to equalize island size. The photoluminescence (PL) full-width at half maximum (FWHM) of 2.5 ML InAs QDs at 0.054 ML/sec was 23 meV at 78K. The PL characteristics of InAs/GaAs QDs were degraded significantly after thermal annealing at 550 oC for 3 hours.

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Li, Zhan Guo, Ming Hui You, Guo Jun Liu, Xin Gao, Lin Li, Zhi Peng Wei, Mei Li, Yong Wang, Xiao Hua Wang et Lian He Li. « Low-Density InAs Quantum Dots Growth by Molecular Beam Epitaxy ». Advanced Materials Research 442 (janvier 2012) : 12–15. http://dx.doi.org/10.4028/www.scientific.net/amr.442.12.

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We investigate the growth of low-density(~4×108cm-2) InAs quantum dots (QDs) on GaAs by molecular beam epitaxy,with emission wavelength up to 1.3 µm at room temperature were achieved. The QDs density are sensitive to growth temperature,growth rate.The optical properties of the QDs annealing temperature used after spacer layer growth that is attributed to the suppressed In segregation from the QDs into the cap layer, reduced the strain in the QDs,significant decrease of integrated PL intensity was observed as the annealing temperature increases.

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Alshehri, Khairiah, Abdelmajid Salhi, Niyaz Ahamad Madhar et Bouraoui Ilahi. « Size and Shape Evolution of GaAsSb-Capped InAs/GaAs Quantum Dots : Dependence on the Sb Content ». Crystals 9, n^o 10 (15 octobre 2019) : 530. http://dx.doi.org/10.3390/cryst9100530.

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Capping InAs/GaAs quantum dots (QDs) with a thin GaAsSb layer alters the QDs structural properties, leading to considerable changes in their optical properties. The increase of the Sb content induces a redshift of the emission energies, indicating a change in the buried QDs shape and size. The presence of well-defined ground- and excited-state emission bands in all the photoluminescence spectra allow an accurate estimation of the buried QDs size and shape by numerical evaluation and tuning of the theoretical emission energies. For an Sb content below 14%, the QDs are found to have a type I band alignment with a truncated height pyramidal form. However, for higher Sb content (22%), the QDs are present in a full pyramidal shape. The observed behavior is interpreted in terms of increasing prevention of InAs QDs decomposition with increasing the Sb content in the cap layer.

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Rakhlin, M. V., K. G. Belyaev, G. V. Klimko, I. S. Mukhin, S. V. Ivanov et A. A. Toropov. « Red single-photon emission from InAs/AlGaAs quantum dots ». Физика и техника полупроводников 52, n^o 4 (2018) : 480. http://dx.doi.org/10.21883/ftp.2018.04.45829.18.

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AbstractWe report on single-photon emission of InAs/AlGaAs self-assembled quantum dots (QDs) grown by molecular beam epitaxy. By varying the growth conditions the QDs luminescence could be tuned over a wide wavelength range from 0.64 to 1 μm, including red part of the visible spectrum. Emission properties of individual QDs are investigated by micro-photoluminescence (μ-PL) spectroscopy using 500-nm-size etched mesa structures. Autocorrelation functions of photons from single QDs, measured in the wide spectral range demonstrate antibunching effect at zero delay time with a value of g ^(2)(0) ~ 0.17 that is a clear evidence of non-classical light.

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Рахлин, М. В., К. Г. Беляев, Г. В. Климко, И. С. Мухин, С. В. Иванов et А. А. Торопов. « Однофотонное излучение квантовых точек InAs/AlGaAs ». Физика твердого тела 60, n^o 4 (2018) : 687. http://dx.doi.org/10.21883/ftt.2018.04.45675.310.

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AbstractThe results of investigation of the radiative characteristics of heterostructures with InAs/AlGaAs quantum dots (QDs) grown by molecular beam epitaxy have been presented. The properties of single QDs were determined by spectroscopy of micro-photoluminescence in cylindrical mesa-structures with a diameter of 200–1000 nm or columnar microresonators with distributed Bragg mirrors. The single-photon nature of the radiation is confirmed by measurements and analysis of the second-order correlation function g ^2(τ) in a wide spectral range from 630 to 730 nm.

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Huang, Xiaoying, Rongbin Su, Jiawei Yang, Mujie Rao, Jin Liu, Ying Yu et Siyuan Yu. « Wafer-Scale Epitaxial Low Density InAs/GaAs Quantum Dot for Single Photon Emitter in Three-Inch Substrate ». Nanomaterials 11, n^o 4 (6 avril 2021) : 930. http://dx.doi.org/10.3390/nano11040930.

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In this work, we successfully achieved wafer-scale low density InAs/GaAs quantum dots (QDs) for single photon emitter on three-inch wafer by precisely controlling the growth parameters. The highly uniform InAs/GaAs QDs show low density of μ0.96/μm2 within the radius of 2 cm. When embedding into a circular Bragg grating cavity on highly efficient broadband reflector (CBR-HBR), the single QDs show excellent optoelectronic properties with the linewidth of 3± 0.08 GHz, the second-order correlation factor g2(τ)=0.0322 ±0.0023, and an exciton life time of 323 ps under two-photon resonant excitation.

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Ruiz, Nazaret, Daniel Fernandez, Esperanza Luna, Lazar Stanojević, Teresa Ben, Sara Flores, Verónica Braza et al. « Tailoring of AlAs/InAs/GaAs QDs Nanostructures via Capping Growth Rate ». Nanomaterials 12, n^o 14 (21 juillet 2022) : 2504. http://dx.doi.org/10.3390/nano12142504.

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The use of thin AlA capping layers (CLs) on InAs quantum dots (QDs) has recently received considerable attention due to improved photovoltaic performance in QD solar cells. However, there is little data on the structural changes that occur during capping and their relation to different growth conditions. In this work, we studied the effect of AlA capping growth rate (CGR) on the structural features of InAs QDs in terms of shape, size, density, and average content. As will be shown, there are notable differences in the characteristics of the QDs upon changing CGR. The Al distribution analysis in the CL around the QDs was revealed to be the key. On the one hand, for the lowest CGR, Al has a homogeneous distribution over the entire surface, but there is a large thickening of the CL on the sides of the QD. As a result, the QDs are lower, lenticular in shape, but richer in In. On the other hand, for the higher CGRs, Al accumulates preferentially around the QD but with a more uniform thickness, resulting in taller QDs, which progressively adopt a truncated pyramidal shape. Surprisingly, intermediate CGRs do not improve either of these behaviors, resulting in less enriched QDs.

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Kim, Hyung Seok, Ju Hyung Suh, Chan Gyung Park, Sang Jun Lee, Sam Kyu Noh, Jin Dong Song, Yong Ju Park, Won Jun Choi et Jung Il Lee. « Microstructures and Growth Characteristics of Self-Assembled InAs/GaAs Quantum Dots Investigated by Transmission Electron Microscopy ». Advanced Materials Research 26-28 (octobre 2007) : 1207–10. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.1207.

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The microstructure and strain characteristics of self-assembled InAs/GaAs quantum dots (QDs) were studied by using transmission electron microscopy. Compressive strain was induced to uncapped QDs from GaAs substrate and the misfit strain largely increased after the deposition of GaAs cap layer. Tensile strain outside QD was extended along the vertical growth direction; up to 15 nm above the wetting layer. Vertically nonaligned and aligned stacked QDs were grown by adjusting the thickness of GaAs spacer layers. The QDs with a lens-shaped morphology were formed in the early stage of growth, and their apex was flattened by the out-diffusion of In atoms upon GaAs capping. However, aligned QDs maintained their lens-shaped structure with round apex after capping. It is believed that their apex did not flatten because the chemical potential gradient of In was relatively low due to the adjacent InAs QD layers.

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FANG, ZHIDAN, ZHENG GONG, ZHENHUA MIAO et ZHICHUAN NIU. « TUNING OF EMISSION WAVELENGTH OF InAs/GaAs QUANTUM DOTS SANDWICHED BY COMBINATION LAYERS ». International Journal of Nanoscience 05, n^o 06 (décembre 2006) : 847–52. http://dx.doi.org/10.1142/s0219581x0600525x.

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We investigate about controlling of photoluminescence (PL) wavelengths of InAs/GaAs self-assembled quantum dots (QDs) sandwiched with combination strained-buffer layer (CSBL) and combination strained-reducing layer (CSRL). The emission peak position of QDs is red-shifted to 1.37 μm. The density of the QDs is increased to 1.17 × 1010 cm -2. It is indicated that optical properties of QDs could be improved by optimizing of the buffer and covering layers for the QDs. These results may provide a new way to further developing GaAs -based 1.3 μm light sources.

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Nowozin, Tobias, Michael Narodovitch, Leo Bonato, Dieter Bimberg, Mohammed N. Ajour, Khaled Daqrouq et Abdullah Balamash. « Room-Temperature Hysteresis in a Hole-Based Quantum Dot Memory Structure ». Journal of Nanotechnology 2013 (2013) : 1–4. http://dx.doi.org/10.1155/2013/797964.

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We demonstrate a memory effect in self-assembled InAs/Al0.9Ga0.1As quantum dots (QDs) near room temperature. The QD layer is embedded into a modulation-doped field-effect transistor (MODFET) which allows to charge and discharge the QDs and read out the logic state of the QDs. The hole storage times in the QDs decrease from seconds at 200 K down to milliseconds at room temperature.

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Suraprapapich, S., S. Thainoi, S. Kanjanachuchai et S. Panyakeow. « Self-Assembled InAs Lateral Quantum Dot Molecules Growth on (001) GaAs by Thin-Capping-and-Regrowth MBE Technique ». Solid State Phenomena 121-123 (mars 2007) : 395–400. http://dx.doi.org/10.4028/www.scientific.net/ssp.121-123.395.

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InAs lateral quantum dot molecules (QDMs) are grown on (001)-GaAs substrates. The self-assembled QDMs are formed in one continuous molecular beam epitaxial (MBE) growth via a thin-capping-and-regrowth technique. Lateral QDMs, each with 10-12 dots arranged in a specific pattern, are determined by the shapes of the underlying nanopropeller quantum dots (QDs). The nanopropeller QDs in turn are obtained by regrowth on nano-holes which have been previously created by capping the first InAs QD layer grown on (001)-GaAs substrate with a thin GaAs layer. The length of the propeller directly influences the number of QDs in a QDM. By varying the conditions for thin-capping, shorter or longer propellers can be achieved, allowing the number of QDs in each QDM to be controlled.

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Kuznetsova, Y. A., F. B. Bayramov, V. V. Toporov, B. H. Bairamov, V. Yu Rud et A. P. Glinushkin. « Recombination radiation of heteroepitaxial structures with InAs quantum dots grown on surface of (311)B GaAs by MBE ». IOP Conference Series : Earth and Environmental Science 1096, n^o 1 (1 octobre 2022) : 012032. http://dx.doi.org/10.1088/1755-1315/1096/1/012032.

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Abstract Dynamics of recombination radiation is found to be fundamental for control the efficiency of quantum dots (QDs) based structures for different range of optoelectronic device applications. We presented results of an experimental study of recombinational radiation of heteroepitaxial strongly confined InAs QD structures with s which are grown up on a surface of the semi-insulating (311)B GaAs substrate by molecular beam epitaxy. It is shown that for the InAs QDs dots, with characteristic dimensions of 12 x 6 nm2, half-width (FWHM) of the observed recombination line attributed to the main electronic fundamental transition of the exciton at 1.1690 meV at T = 77 K is 41.58 meV. This value of FWHM is substantially less than typical literature values obtained under comparable experimental conditions for heteroepitaxial structures with InAs QDs, grown on vicinal surfaces of (100) GaAs substrate with angle of disorientation 7° relative to direction [001].

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Sánchez Trujillo, Diego Javier, Jhon Jairo Prías Barragán, Hernando Ariza Calderón, Álvaro Orlando Pulzara Mora et Máximo López López. « Photoreflectance study of the GaAs buffer layer in InAs/GaAs quantum dots ». Superficies y Vacío 30, n^o 4 (15 décembre 2017) : 56–60. http://dx.doi.org/10.47566/2017_syv30_1-040056.

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GaAs buffer layer in InAs/GaAs quantum dots (QDs) was investigated by Photoreflectance (PR) technique at 300 K. PR spectra obtained were compared with commercial GaAs sample PR spectra, and they were analyzed by using the derivative Lorentzian functions as proposed by Aspnes in the middle field regimen. PR spectra in InAs/GaAs QDs sample was attributed to the photoreflectance response in the GaAs buffer layer. Band bending energies were calculated for laser intensities from 1 mW to 21 mW. The photoreflectance comparative study in the samples was realized considering the difference in the parameters: electric field on the surface, broadening parameter, energy gained by photoexcited carriers due to the electric field applied, frequency of light and heavy holes and band bending energy values. The results suggest that the presence of InAs quantum dots increases the light and heavy holes frequencies and the band bending energy values; and decreases the electric field on the surface, the broadening parameter and the energy gained by photoexcited carriers. We found that InAs QDs presence modifies the surface electrical field around one order of magnitude in the GaAs buffer layer and this behavior can be attributed to surface passivation.

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Bochorishvili, Beka, et Hariton M. Polatoglou. « Interacting Double InAs/GaAs Quantum Dots of Cylindrical Symmetry ». Journal of Nano Research 10 (avril 2010) : 87–92. http://dx.doi.org/10.4028/www.scientific.net/jnanor.10.87.

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The electron and hole energy states and oscillator strengths for interband transitions of two interacting Quantum dots (QDs) are theoretically studied. We explore how the properties of the system depend on the distance between them. Calculations are done for InAs QDs which are embedded in GaAs. The QDs have cylindrical form and are situated one on top of the other in such way that their symmetry axes coincide. The calculations are done in the envelope function approximation using position dependent effective masses. Finite Element Method (FEM) is utilized to find energy spectra, wavefunctions and oscillator strengths. We find that the hole states show less tunneling compared to the electron states, transitions in general show some anisotropy which decreases as the distance between the dots decrease and that the total oscillator strength for each particular transition is constant.

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Oshima, Jin, Nobuhiko Ozaki, Hisaya Oda, Eiichiro Watanabe, Hirotaka Ohsato, Naoki Ikeda, Yoshimasa Sugimoto et Richard A. Hogg. « Near-infrared dual-wavelength surface-emitting light source using InAs quantum dots resonant with vertical cavity modes ». Japanese Journal of Applied Physics 61, SD (24 mars 2022) : SD1003. http://dx.doi.org/10.35848/1347-4065/ac5b24.

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Abstract We developed a compact dual-wavelength surface-emitting light source using InAs quantum dots (QDs) embedded in a vertical cavity (VC). The VC was designed to possess two optical cavity modes that resonate with the discrete emission lines of the QDs. The fabricated light source exhibited significant enhancements in the vertical light emission corresponding to the VC modes. In addition, the light source demonstrated selectivity to the enhanced emission wavelengths with changes in temperature. Compared to conventional dual-wavelength vertical external cavity surface-emitting lasers, these QD-based dual-wavelength emission devices allow for the realization of simple structures because the InAs QDs act as dual-light-emitting materials. These results can be applied to simple dual-wavelength surface-emitting light sources.

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Janney, Eathan, et Guillermo Muñoz-Matutano. « Interactive Musical Display of Quantum Dot Emission Spectra ». Leonardo 49, n^o 5 (octobre 2016) : 440–41. http://dx.doi.org/10.1162/leon_a_01293.

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Quantum dots (QDs) are zero-dimensional semiconductor nanostructures composed of thousands of atoms. QDs are often referred to as artificial atoms because their small structure results in unique, atom-like behavior; like atoms, QDs have optical emission at discrete wavelengths. Here the authors describe a novel method to interactively learn about the spectral properties of QDs using musical intuitions. They transform spectral information from selected Indum Arsenide (InAs) QDs into musical information, including both pitch and rhythm. Thus, they generate a multisensory experience of spectral information allowing users to learn about the range of frequencies of QDs as well as their unique spectral properties resulting from coulombic interactions.

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Yang, B., et E. Pan. « Elastic Fields of Quantum Dots in Multilayered Semiconductors : A Novel Green’s Function Approach ». Journal of Applied Mechanics 70, n^o 2 (1 mars 2003) : 161–68. http://dx.doi.org/10.1115/1.1544540.

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We present an efficient and accurate continuum-mechanics approach to predict the elastic fields in multilayered semiconductors due to buried quantum dots (QDs). Our approach is based on a novel Green’s function solution in anisotropic and linearly elastic multilayers, derived within the framework of generalized Stroh formalism and Fourier transforms, in conjunction with the Betti’s reciprocal theorem. By using this approach, the induced elastic fields due to QDs with general misfit strains are expressed as a volume integral over the QDs domains. For QDs with uniform misfit strains, the volume integral involved is reduced to a surface integral over the QDs boundaries. Further, for QDs that can be modeled as point sources, the induced elastic fields are then derived as a sum of the point-force Green’s functions. In the last case, the solution of the QD-induced elastic field is analytical, involving no numerical integration, except for the evaluation of the Green’s functions. As numerical examples, we have studied a multilayered semiconductor system of QDs made of alternating GaAs-spacer and InAs-wetting layers on a GaAs substrate, plus a freshly deposited InAs-wetting layer on the top. The effects of vertical and horizontal arrays of QDs and of thickness of the top wetting layer on the QD-induced elastic fields are examined and some new features are observed that may be of interest to the designers of semiconductor QD superlattices.

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Zhou, G. Y., Y. H. Chen, X. L. Zhou, B. Xu, X. L. Ye et Z. G. Wang. « Different growth mechanisms of bimodal InAs/GaAs QDs ». Physica E : Low-dimensional Systems and Nanostructures 43, n^o 1 (novembre 2010) : 308–11. http://dx.doi.org/10.1016/j.physe.2010.08.001.

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Jia, Guo-zhi, Jiang-hong Yao, Yong-chun Shu, Xiao-dong Xing et Biao Pi. « Quantum rings formed in InAs QDs annealing process ». Applied Surface Science 255, n^o 8 (février 2009) : 4452–55. http://dx.doi.org/10.1016/j.apsusc.2008.11.042.

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Wang, Kun, Qiang He, Deren Yang et Xiaodong Pi. « Highly Efficient Energy Transfer from Silicon to Erbium in Erbium-Hyperdoped Silicon Quantum Dots ». Nanomaterials 13, n^o 2 (9 janvier 2023) : 277. http://dx.doi.org/10.3390/nano13020277.

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Erbium-doped silicon (Er-doped Si) materials hold great potential for advancing Si photonic devices. For Er-doped Si, the efficiency of energy transfer (ηET) from Si to Er3+ is crucial. In order to achieve high ηET, we used nonthermal plasma to synthesize Si quantum dots (QDs) hyperdoped with Er at the concentration of ~1% (i.e., ~5 × 1020 cm−3). The QD surface was subsequently modified by hydrosilylation using 1-dodecene. The Er-hyperdoped Si QDs emitted near-infrared (NIR) light at wavelengths of ~830 and ~1540 nm. An ultrahigh ηET (~93%) was obtained owing to the effective energy transfer from Si QDs to Er3+, which led to the weakening of the NIR emission at ~830 nm and the enhancement of the NIR emission at ~1540 nm. The coupling constant (γ) between Si QDs and Er3+ was comparable to or greater than 1.8 × 10−12 cm3·s−1. The temperature-dependent photoluminescence and excitation rate of Er-hyperdoped Si QDs indicate that strong coupling between Si QDs and Er3+ allows Er3+ to be efficiently excited.

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LIN, Y. G., C. H. WU, S. L. TYAN, S. D. LIN et C. P. LEE. « PHOTOLUMINESCENCE OF ULTRA SMALL InAs/GaAs QUANTUM DOTS ». Modern Physics Letters B 19, n^o 18 (10 août 2005) : 907–17. http://dx.doi.org/10.1142/s021798490500892x.

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The InAs/GaAs quantum dots (QDs) with a baselength of less than 10 nm are studied by the excitation-, temperature-dependent and magneto-photoluminescence (PL). The baselengths of the QDs, calculated by the PL ground state transition energy and estimated by magneto-PL spectra, are in agreement with the result of atomic force microscopy measurements. By means of the excitation-dependent PL, we demonstrate that only the ground electron and hole states exist when the baselength of the QDs is smaller than about 7.3 nm, whereas the larger dots with a baselength of about 8.7 nm will give rise to one excited hole state. The measured energy separation between the ground and the excited hole states is in good agreement with the theoretical calculation. The transition energy in temperature-dependent PL spectra shows a rapid redshift as the temperature is higher than the critical temperature. The redshift rate is about 2.8 and 2.5 times larger than the values calculated by Varshni's law for small and large dots respectively. The higher redshift rate can be explained by the stronger tunneling effect. In addition, the PL linewidths show a V-shape dependence with the temperature. This behavior could be well described as a tunneling and electron-phonon scattering effect.

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Islam, Sk Masiul, et P. Banerji. « Size effect of InAs quantum dots grown by metal organic chemical vapor deposition technique in storing electrical charges for memory applications ». RSC Advances 5, n^o 9 (2015) : 6906–11. http://dx.doi.org/10.1039/c4ra13317j.

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Liu, Guang Yan, et Wen Cai Wang. « Growth and Characterization of InAs Quantum Dots on GaAsSb ». Applied Mechanics and Materials 184-185 (juin 2012) : 1001–5. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.1001.

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The growth details of strained GaAsSb layers on GaAs(001) substrates were studied by reflection high energy electron diffraction (RHEED) beam intensity oscillations as a function of both substrate temperature and Sb/As flux ratio. Both the RHEED intensity and RHEED oscillation cycles are reduced with decreasing substrate temperature and Sb/As flux ratio. InAs QDs with high dot density, small dot size and narrow size distribution have been achieved on strained GaAs / GaAsSb buffer layer. The average lateral size of dots shows a trend toward to smaller size and dots’ density shows a trend toward to higher density as the surface Sb composition increasing. The QDs with higher density and smaller size distributions at high Sb composition, indicates that the Sb plays an important role in the dot formation under this growth condition. The lattice mismatch of InAs layer with the GaAsSb buffer layer is reduced with increasing of Sb composition in the GaAsSb interlayer. This result indicates that the density, size and size distribution of self-assembled quantum dots (QDs) can be controlled through the manipulation of the Sb-mediated strain field in the lattice mismatched system.

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Holewa, Paweł, Jakub Jasiński, Artem Shikin, Elizaveta Lebedkina, Aleksander Maryński, Marcin Syperek et Elizaveta Semenova. « Optical Properties of Site-Selectively Grown InAs/InP Quantum Dots with Predefined Positioning by Block Copolymer Lithography ». Materials 14, n^o 2 (14 janvier 2021) : 391. http://dx.doi.org/10.3390/ma14020391.

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The InAs/InP quantum dots (QDs) are investigated by time-integrated (PL) and time-resolved photoluminescence (TRPL) experiments. The QDs are fabricated site-selectively by droplet epitaxy technique using block copolymer lithography. The estimated QDs surface density is ∼1.5 × 1010 cm−2. The PL emission at T=300 K is centered at 1.5 μm. Below T=250 K, the PL spectrum shows a fine structure consisting of emission modes attributed to the multimodal QDs size distribution. Temperature-dependent PL reveals negligible carrier transfer among QDs, suggesting good carrier confinement confirmed by theoretical calculations and the TRPL experiment. The PL intensity quench and related energies imply the presence of carrier losses among InP barrier states before carrier capture by QD states. The TRPL experiment highlighted the role of the carrier reservoir in InP. The elongation of PL rise time with temperature imply inefficient carrier capture from the reservoir to QDs. The TRPL experiment at T=15 K reveals the existence of two PL decay components with strong dispersion across the emission spectrum. The decay times dispersion is attributed to different electron-hole confinement regimes for the studied QDs within their broad distribution affected by the size and chemical content inhomogeneities.

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Boonpeng, P., S. Panyakeow et S. Ratanathammaphan. « In–Mole-Fraction and Thickness of Ultra-Thin InGaAs Insertion Layers Effects on the Structural and Optical Properties of InAs Quantum Dots ». Advanced Materials Research 31 (novembre 2007) : 132–34. http://dx.doi.org/10.4028/www.scientific.net/amr.31.132.

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InAs quantum dots (QDs) have been grown by solid-source molecular beam epitaxy on different InxGa1-xAs (0 ≤ x ≤ 0.3) to investigate the effect of In-mole-fraction and thickness of InGaAs insertion layer (IL) on the structural and optical properties of the QDs. The density of QDs directly grown on GaAs is 1×1010 cm-2, and increase to 1.4-1.8×1010 cm-2 on InGaAs layers which depend on the In-mole-fraction and thickness of InGaAs layers. The effects of In-mole-fraction and thickness of InGaAs insertion layer on optical properties of the QDs are studied by photoluminescence (PL). The FWHM of PL spectrum corresponds to the size distribution of the QDs.

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KRYZHANOVSKAYA, N. V., A. G. GLADYSHEV, S. A. BLOKHIN, A. P. VASIL'EV, E. S. SEMENOVA, A. E. ZHUKOV, M. V. MAXIMOV et al. « HIGH TEMPERATURE STABILITY OF OPTICAL PROPERTIES OF InAs QUANTUM DOTS REALIZED BY CONTROLLING OF QUANTUM DOTS ELECTRONIC SPECTRUM ». International Journal of Nanoscience 06, n^o 03n04 (juin 2007) : 283–86. http://dx.doi.org/10.1142/s0219581x07004742.

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The optical properties of InAs /( Al ) GaAs quantum dots (QDs) overgrowth by thin AlAs / InAlAs layers are studied as a function of temperature from 10 to 500 K. The QDs emit at 1.27 μm at room temperature. It is shown that the QD energetic spectrum can be tuned by overgrowth of AlAs / InAlAs to provide high temperature stability of the QDs optical properties. Transport of carriers between neighboring QDs is absent, and the carrier distribution remains nonthermal up to room temperature. It is shown that suppression of the thermal escaping of the carriers from QDs is conditioned by high energy separation between ground and excited states, absence of wetting layer level, and increase of carrier localization energy in QDs in case of the Al 0.3 Ga 0.7 As matrix.

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Ilahi, Bouraoui, Manel Souaf, Mourad Baira, Jawaher Alrashdi, Larbi Sfaxi, Abdulaziz Alhazaa et Hassen Maaref. « Evolution of InAs/GaAs QDs Size with the Growth Rate : A Numerical Investigation ». Journal of Nanomaterials 2015 (2015) : 1–6. http://dx.doi.org/10.1155/2015/847018.

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This paper investigates the impact of the deposition rate on the mean buried InAs/GaAs quantum dots’ (QDs) size by means of a coupled photoluminescence spectroscopy and numerical approach. The proposed method consists in tuning the theoretical transition energies by changing the QDs aspect ratio towards best fit of the photoluminescence emission energies arising from the state filling effect. The electron-hole confined states are obtained by solving the single particle one band effective mass Schrödinger equation in cylindrical coordinates for a lens shaped QD by finite element method taking into account the strain effects. The obtained evolution is in agreement with morphological data taken from similar uncapped QDs samples.

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Qiu, Zheng Rong, et Hong Yu. « Optical Properties of Silicon Quantum Dots ». Key Engineering Materials 483 (juin 2011) : 760–64. http://dx.doi.org/10.4028/www.scientific.net/kem.483.760.

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A first-principles study of the optical properties of silicon quantum dots (Si QDs) with different diameters is presented in this paper. Si QDs consisting of 10-220 Si atoms, the corresponding diameter ranges from 6-20 Å, with full termination of the Si interface with H are investigated in detail. The results show that both the band gap and the absorption spectrum of Si QDs are size-dependent. For Si QDs with diameter ranges from 6-20 Å, as the diameter decreases, the band gap increases, and a considerable blue-shift in the absorption spectrum is occurred. This unique property can be used to extend the absorption spectrum of the solar cell by mixing in QDs with different sizes. Therefore, the full spectrum of the sunlight may be utilized more efficiently.

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Tanaka, Motoyuki, Keichiro Banba, Tomah Sogabe et Koichi Yamaguchi. « InAs/GaAsSb in-plane ultrahigh-density quantum dot lasers ». Applied Physics Express 14, n^o 12 (22 novembre 2021) : 124002. http://dx.doi.org/10.35848/1882-0786/ac3542.

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Abstract InAs in-plane ultrahigh-density quantum dots (IP-UHD QDs) were grown on GaAsSb/GaAs(001) by molecular beam epitaxy and introduced into the active layer of a ridge-waveguide AlGaAs/GaAs laser. The IP-UHD QD density was 5 × 1011 cm−2. Despite having a short cavity length, no high-reflective coating on the cavity edge and a small number of stacked QD layers, stable laser operation up to 80 ℃ has been achieved. IP-UHD QD lasers without p-type doping exhibited a characteristic temperature of 77 K. IP-UHD QD lasers have the same low internal loss as conventional QD lasers. Improved uniformity in IP-UHD QDs promises the achievement of ultralow threshold current.

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Yin, Zong You, Xiao Hong Tang, Ji Xuan Zhang, Deny Sentosa, Jing Hua Teng, An Yan Du et Mee Koy Chin. « Morphology and Crystal Quality of InAs QDs Grown by MOVPE Using Different Growth Modes ». Advanced Materials Research 31 (novembre 2007) : 17–19. http://dx.doi.org/10.4028/www.scientific.net/amr.31.17.

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Morphology and crystal-quality of InAs/In0.53Ga0.47As/InP quantum dots (QDs) grown by metal-organic vapor phase epitaxy (MOVPE) in N2 ambient using different growth modes have been studied. It is found that the morphology and crystal-quality of InAs QDs are dependant on the growth modes. After optimizing the dots’ growth modes, dots’ size dispersion and crystal-quality are both improved greatly, resulting in the enhancement factor of ∼ 2.9 in the photoluminescence (PL) peak-intensity from single QD. When the dots are buried, the dot size decrease compared with the free-standing dots due to the soon capping layer deposition during dots’ being buried. The thermal activation energy measured is comparable to the valence-band offset in the QD system calculated by 8 kp theory model. This indicates the PL quenching induced by the interface defects is suppressed due to the defect density lowering in the QDs grown by such optimized growth mode.

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Sala, Elisa M., Max Godsland, Young In Na, Aristotelis Trapalis et Jon Heffernan. « Droplet epitaxy of InAs/InP quantum dots via MOVPE by using an InGaAs interlayer ». Nanotechnology 33, n^o 6 (19 novembre 2021) : 065601. http://dx.doi.org/10.1088/1361-6528/ac3617.

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Abstract InAs quantum dots (QDs) are grown on an In0.53Ga0.47As interlayer and embedded in an InP(100) matrix. They are fabricated via droplet epitaxy (DE) in a metal organic vapor phase epitaxy (MOVPE) reactor. Formation of metallic indium droplets on the In0.53Ga0.47As lattice-matched layer and their crystallization into QDs is demonstrated for the first time in MOVPE. The presence of the In0.53Ga0.47As layer prevents the formation of an unintentional non-stoichiometric 2D layer underneath and around the QDs, via suppression of the As-P exchange. The In0.53Ga0.47As layer affects the surface diffusion leading to a modified droplet crystallization process, where unexpectedly the size of the resulting QDs is found to be inversely proportional to the indium supply. Bright single dot emission is detected via micro-photoluminescence at low temperature, ranging from 1440 to 1600 nm, covering the technologically relevant telecom C-band. Transmission electron microscopy investigations reveal buried quantum dots with truncated pyramid shape without defects or dislocations.

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Le, Thu-Huong, Dang Thi Thanh Le et Nguyen Van Tung. « Synthesis of Colloidal Silicon Quantum Dot from Rice Husk Ash ». Journal of Chemistry 2021 (2 mars 2021) : 1–9. http://dx.doi.org/10.1155/2021/6689590.

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This article describes the synthesis procedure of colloidal silicon quantum dot (Si QDs) from rice husk ash. The silicon quantum dots were capped with 1-octadecene by thermal hydrosilylation under argon gas to obtain octadecyl-Si QDs (ODE-Si QDs). The size separation of ODE-Si QDs was examined by the column chromatography method, which used silica gel (40–63 μm) as the stationary phase. Finally, we obtained two fractions of silicon quantum dot, exhibiting blue emission (B-Si QDs) with an average size of 2.5 ± 0.73 nm and red emission (R-Si QDs) with an average size of 5.1 ± 0.68 nm under a UV lamp (365 nm). The PL spectra of B-Si QDs and R-Si QDs samples show maximum peak energy at 410 nm (3.02 eV) and 700 nm (1.77 eV), respectively, while the quantum yield of Si QDs decreases from 5.8 to 34.6% when the average size decreases from 2.5 nm to 5.1 nm. The above results of PL emission spectroscopy and UV-vis absorption show quantum confined effect in Si QDs.

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Shang, Xiangjun, Hanqing Liu, Xiangbin Su, Shulun Li, Huiming Hao, Deyan Dai, Zesheng Chen, Haiqiao Ni et Zhichuan Niu. « Light Hole Excitons in Strain-Coupled Bilayer Quantum Dots with Small Fine-Structure Splitting ». Crystals 12, n^o 8 (10 août 2022) : 1116. http://dx.doi.org/10.3390/cryst12081116.

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In this work, we measure polarization-resolved photoluminescence spectra from excitonic complexes in tens of single InAs/GaAs quantum dots (QDs) at the telecom O-band with strain-coupled bilayer structure. QDs often show fine-structure splitting (FSS) ~100 μeV in uniform anisotropy and valence-band mixing of heavy holes (HH) and light holes (LH); the biaxial strain also induces LH excitons with small FSS (especially XX, <5 μeV, 70% of QDs); delocalized LH reduces the Coulomb interaction between holes Vhh and enhances population on LH excitons XX, XX11, X11+ and XX21+.

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Семенов, M. Б., В. Д. Кревчик, Д. O. Филатов, A. В. Шорохов, A. П. Шкуринов, И. А. Ожередов, П. В. Кревчик et al. « Диссипативное туннелирование электронов в вертикально связанных двойных асимметричных квантовых точках InAs/GaAs(001) ». Журнал технической физики 91, n^o 10 (2021) : 1431. http://dx.doi.org/10.21883/jtf.2021.10.51354.66-21.

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We report on the results of experimental studies of the photoelectric properties of a GaAs p-i-n photodiode with InAs/GaAs(001) double asymmetric quantum dots (DAQDs) grown by self-assembling in Metal Organic Vapor Phase Epitaxy (MOVPE) process. Three peaks were observed in the dependence of the photocurrent on the reverse bias measured at monochromatic photoexcitation of the DAQDs at the wavelength corresponding to the energy of interband optical transitions between the ground hole and electron states in the bigger QDs. These peaks were related to the tunneling of the photoexcited electrons between the QDs including the dissipative one (with emission and absorption of the optical phonons). The experimental results agree qualitatively with the theoretical field dependence of the 1D dissipative tunneling probability between the QDs.

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Wang, Tong, Tim J. Puchtler, Saroj K. Patra, Tongtong Zhu, Muhammad Ali, Tom J. Badcock, Tao Ding, Rachel A. Oliver, Stefan Schulz et Robert A. Taylor. « Direct generation of linearly polarized single photons with a deterministic axis in quantum dots ». Nanophotonics 6, n^o 5 (21 juillet 2017) : 1175–83. http://dx.doi.org/10.1515/nanoph-2017-0027.

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AbstractWe report the direct generation of linearly polarized single photons with a deterministic polarization axis in self-assembled quantum dots (QDs), achieved by the use of non-polar InGaN without complex device geometry engineering. Here, we present a comprehensive investigation of the polarization properties of these QDs and their origin with statistically significant experimental data and rigorous k·p modeling. The experimental study of 180 individual QDs allows us to compute an average polarization degree of 0.90, with a standard deviation of only 0.08. When coupled with theoretical insights, we show that these QDs are highly insensitive to size differences, shape anisotropies, and material content variations. Furthermore, 91% of the studied QDs exhibit a polarization axis along the crystal [1–100] axis, with the other 9% polarized orthogonal to this direction. These features give non-polar InGaN QDs unique advantages in polarization control over other materials, such as conventional polar nitride, InAs, or CdSe QDs. Hence, the ability to generate single photons with polarization control makes non-polar InGaN QDs highly attractive for quantum cryptography protocols.

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Ikeri, H. I., A. I. Onyia et F. N. Kalu. « Hot carrier exploitation strategies and model for efficient solar cell applications ». Chalcogenide Letters 18, n^o 11 (novembre 2021) : 745–57. http://dx.doi.org/10.15251/cl.2021.1811.745.

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Hot carriers are electrons or holes that are created in semiconductors upon the absorption of photons with energies greater than the fundamental bandgap. The excess energy of the hot carrier cools to the lattice temperature via carrier–phonon scattering and wasted as heat in [the] picoseconds timescale. The hot-carrier cooling represents a severe loss in the solar cells that have significantly limits their power conversion efficiencies. Hot carrier solar cells aim to mitigate this optical limitation by effective utilization of carriers at elevated energies. However, exploitation of hot carrier energy is extremely challenging as hot carriers rapidly lose their excess energy in phonon emission and therefore requires a substantial delay of carrier cooling in absorber material. In this paper a simple model was formulated to study the kinetic energies and hence the energy levels of the photo excited carriers in the quantum dots (QDs) whereas Schaller model was used to investigate the threshold energies of considered QDs. Results strongly indicate low threshold photon energies within the energy conservation limit for PbSe, PbTe, PbS, InAs, and InAs QDs. These materials seem to be good candidates for efficient carrier multiplication. It is found also that PbSe, PbTe, PbS, InAs, ZnS and InAs QDs exhibit promising potential for possible hot carrier absorber due to their widely spaced energy levels predicted to offer a large phononic gap between the optical and acoustic branches in the phonon dispersion. This in principle enhances phonon bottleneck effect that dramatically slows down hot carrier cooling leading to retention of hot carriers long enough to enable their exploitation. Two novel strategies were employed for the conversion of hot carriers into usable energies. The first approach involves the extraction of the energetic hot carriers while they are ‘hot’ to create higher photo voltage while the second approach uses the hot carrier to produce more carriers through impact ionization to create higher photo current. These mechanisms theoretically give rise to high overall conversion efficiencies of hot carrier energy well above Shockley and Queisser limit of conventional solar cells.

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Shi, G. X., Bo Xu, P. Jin, X. L. Ye, C. X. Cui, C. L. Zhang, J. Wu et Z. G. Wang. « The Structural and Photoluminescence Character of InAs Quantum Dots Grown on a Combined InAlAs and GaAs Strained Buffer Layer ». Materials Science Forum 475-479 (janvier 2005) : 1791–94. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.1791.

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The structural and photoluminescence (PL) properties of the InAs quantum dots (QDs) grown on a combined InAlAs and GaAs strained buffer layer have been investigated by AFM and PL measurements. The dependence of the critical thickness for the transition from 2D to 3D on the thickness of GaAs layer is demonstrated directly by RHEED. The effects of the introduced-InAlAs layer on the density and the aspect ratio of QDs have been discussed.

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Liu, Jian Qing, Yong Hai Chen, Bo Xu et Zhan Guo Wang. « Growth of InAs Quantum Wires with Ga-Assisted Deoxidation on Cleaved-Edge GaAs (110) Surface ». Advanced Materials Research 341-342 (septembre 2011) : 73–76. http://dx.doi.org/10.4028/www.scientific.net/amr.341-342.73.

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We have fabricated site-controlled InAs quantum wires (QWRs) on the cleaved surface (110) of AlGaAs/GaAs superlattices (SLs) structures by using Ga-assisted deoxidation method. In the surface of SLs regions, InAs QWRs were nucleated on GaAs in stead of AlGaAs. In the (110) surface without superlattices(SLs) structures, QDs with a large size were obtained, which is considered hard to realize. To understand the different InAs growth phenomena in the regions with and without superlattices structures, we suggest that indium adatoms have an apparent trend to migrate to the SLs area.

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STIFF-ROBERTS, ADRIENNE D. « HYBRID NANOMATERIALS FOR MULTI-SPECTRAL INFRARED PHOTODETECTION ». International Journal of High Speed Electronics and Systems 17, n^o 01 (mars 2007) : 165–72. http://dx.doi.org/10.1142/s0129156407004382.

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Quantum dot infrared photodetectors (QDIPs) using quantum dots (QDs) grown by strained-layer epitaxy have demonstrated low dark current, multi-spectral response, high operating temperature, and infrared (IR) imaging. However, achieving near room-temperature, multi-spectral operation is a challenge due to randomness in QD properties. The ability to control dopant incorporation is important since charge carrier occupation influences dark current and IR spectral response. In this work, dopant incorporation is investigated in two classes of QDs; epitaxial InAs/GaAs QDs and CdSe colloidal QDs (CQDs) embedded in MEH-PPV conducting polymers. The long-term goal of this work is to combine these hybrid nanomaterials in a single device heterostructure to enable multi-spectral IR photodetection. Two important results towards this goal are discussed. First, by temperature-dependent dark current-voltage and polarization-dependent Fourier transform IR spectroscopy measurements in InAs/GaAs QDIPs featuring different doping schemes, we have provided experimental evidence for the important contribution of thermally-activated, defect-assisted, sequential resonant tunneling. Second, the enhanced quantum confinement and electron localization in the conduction band of CdSe / MEH-PPV nanocomposites enable intraband transitions in the mid-IR at room temperature. Further, by controlling the semiconductor substrate material, doping type, and doping level on which these nanocomposites are deposited, the intraband IR response can be tuned.

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Chatzarakis, N. G., E. A. Amargianitakis, S. Germanis, A. Stavrinidis, G. Konstantinidis, Z. Hatzopoulos et N. T. Pelekanos. « Redshifted biexciton and trion lines in strongly confined (211)B InAs/GaAs piezoelectric quantum dots ». Journal of Applied Physics 131, n^o 12 (28 mars 2022) : 123101. http://dx.doi.org/10.1063/5.0084931.

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The emission lines of strongly confined (211)B InAs/GaAs quantum dots (QDs), embedded in short-period GaAs/AlAs superlattices, are thoroughly characterized by a range of single-dot spectroscopy techniques, including cross correlation photon-counting measurements. Contrary to what is expected for a piezoelectric QD system, the single-dot biexciton line is found redshifted with respect to the exciton one by as many as 6 meV. This comes in striking contrast to previous reports on the same QD system, without additional confinement, where the biexciton lines always showed up at higher energies than the exciton, by 4–13 meV. In addition, two charged exciton lines are identified for the first time in a piezoelectric InAs-based QD. A positively charged (Χ+) and a negatively charged (Χ−) trion line are observed 1.5 and 7.5 meV below the neutral exciton line, respectively. Our results pave the way to an enhanced understanding of the excitonic transitions in (211)B QDs and highlight the possible role of strong confinement and accompanying correlation effects as a means to tailor the transition energies of multi-particle states in semiconductor QDs.

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Hansen, L., A. Ankudinov, F. Bensing, J. Wagner, G. Ade, P. Hinze, V. Wagner, J. Geurts et A. Waag. « Growth and Characterization of Inas Quantum Dots on Silicon ». MRS Proceedings 583 (1999). http://dx.doi.org/10.1557/proc-583-33.

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AbstractUp to 1011 cm−2 InAs quantum dots (QD) can be grown on Silicon(001) by molecular beam epitaxy. This very new material system is on the one hand interesting with regard to the integration of optoelectronics with silicon technology on the other hand it offers new insight into the formation of QDs. We report on RHEED, TEM and Raman studies about (in-) coherence of the QDs and on an according to our knowledge so far unknown dewetting transition in this material system. The results are being discussed on the basis of a thermodynamic model, assuming a liquid-like behavior of a strained adlayer.

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Holewa, Paweł, Shima Kadkhodazadeh, Michał Gawełczyk, Paweł Baluta, Anna Musiał, Vladimir G. Dubrovskii, Marcin Syperek et Elizaveta Semenova. « Droplet epitaxy symmetric InAs/InP quantum dots for quantum emission in the third telecom window : morphology, optical and electronic properties ». Nanophotonics, 28 janvier 2022. http://dx.doi.org/10.1515/nanoph-2021-0482.

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Abstract The rapidly developing quantum communication technology requires deterministic quantum emitters that can generate single photons and entangled photon pairs in the third telecom window, in order to be compatible with existing optical fiber networks and on-chip silicon photonic processors. InAs/InP quantum dots (QDs) are among the leading candidates for this purpose, due to their high emission efficiency in the required spectral range. However, fabricating versatile InAs/InP QD-based quantum emitters is challenging, especially as these QDs typically have asymmetric profiles in the growth plane, resulting in a substantial bright-exciton fine structure splitting (FSS). This hinders the generation of entangled photon pairs and thus, compromises the versatility of InAs/InP QDs. We overcome this by implementing droplet epitaxy (DE) synthesis of low surface density (2.8 × 108 cm−2) InAs x P1−x QDs with x = (80 ± 15)% on an (001)-oriented InP substrate. The resulting QDs are located in etched pits, have concave bases, and most importantly, have symmetric in-plane profiles. We provide an analytical model to explain the kinetics of pit formation and QD base shape modification. Our theoretical calculations of electronic states reveal the properties of neutral and charged excitons and biexcitons confined in such QDs, which agree with the optical investigations of individual QDs. The optical response of QDs' ensemble suggests that FSS may indeed be negligible, as reflected in the vanishing degree of linear polarization. However, single QD spectrum gathered from an etched mesa shows moderate FSS of (50 ± 5) µeV that we link to destructive changes made in the QD environment during the post-growth processing. Finally, we show that the studied DE QDs provide a close-to-ideal single-photon emission purity of (92.5 ± 7.5)% in the third telecom window.

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