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Role of Sb on the vertical-alignment of type-II strain-coupled InAs/GaAsSb multi quantum dots structures
摘要： The implementation of GaAs0.8Sb0.2 as CL to obtain type-II strain-coupled InAs MQD structures has been examined and compared to similar structures without Sb or without strain coupling. First, it has been demonstrated that capping with GaAsSb prevents the formation of In-rich agglomerations that hampered the QD formation as it has been observed in the sample without Sb. Instead, it promotes the vertical alignment (VA) of almost all QDs with a high density of QD columns. Second, there is a preferential Sb accumulation over the dots together with an undulation of the growth front, contrary to the observed in the uncoupled structure. In case of a deficient covering of GaAsSb, as occurs for giant QDs, In-rich agglomerations may develop. Each VAQD column consists of a sequence of alternating quantum blocks of pyramid-shaped In(Ga)As separated by GaAsSb blocks that rest over them. These Sb-rich blocks are not homogeneous accumulating around the pyramidal apex like a collar. Between the columns, there is an impoverishment of In and Sb compared to the uncoupled sample. These columns can behave as self-aligned nanowires with type II band alignment between self-assembled InAs and GaAsSb quantum blocks that opens new opportunities for novel devices.
关键词： GaAsSb capping layer,III-V semiconductors alloys,Transmission electron microscopy,Composition distribution,Vertical aligned quantum dots
更新于2025-09-23 15:21:01
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Resonance fluorescence of a single semiconductor quantum dot: the impact of a fluctuating electrostatic environment
摘要： Semiconductor quantum dots are very efficient sources of single and highly indistinguishable photons. These properties rely on the possibility to coherently control the system at the single spin level. At this ultimate level of control, the quantum dot becomes a very sensitive probe of its solid-state environment and any interaction turns into a dephasing process that alters its coherence properties. In this topical review, we give an overview of the issue of charge noise which remains one of the main dephasing mechanisms to overcome. This phenomenon which strongly depends on sample preparation, originates from a fluctuating electrostatic landscape around the quantum dots and renders a unified description quite awkward. We present the common characteristic features induced by charge noise that have been observed in the resonant fluorescence experiments of single quantum dots and discuss the different approaches that have been proposed in the literature to circumvent this problem.
关键词： quantum dots,quantum coherence,optical properties,resonance fluorescence,excitons,III–V semiconductors
更新于2025-09-23 15:19:57
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Highly luminescent blue-emitting In <sub/>1a??x</sub> Ga <sub/>x</sub> P@ZnS quantum dots and their applications in QLEDs with inverted structure
摘要： In order to resolve the issues of uncontrollably high reactivity of tris(trimethylsilyl)phosphine, widely used P precursor, and very low solubility of metal halide precursors in non-coordinating solvent with ligands in the synthesis of environmentally benign III-V quantum dots, we created bis(trimethylsilyl)phosphine, HP(TMS)2, new P precursor with controllable reactivity and new metal complex precursors (Indium-trioctylphosphine, In-TOP; Ga-TOP; Zn-TOP) soluble in octadecene, non-coordinating solvent with dodecanethiol, C12SH. Another challenging issue with III-V quantum dots is to generate highly luminescent photostable blue-emitting nanaocrystals. We present the way of synthesizing pure III-V In1-xGaxP blue-emitting alloy core in non-coordination solvent. Gallium is introduced in the core to adjust the exciton energy effectively and to lessen lattice mismatch with zinc sulfide shell which contributes to the removal of surface defects and the enhancement of the photostability, and thus enhancing the photoluminescent quantum yield (PLQY) and the high color purity of quantum dots with narrow full width at half maximum (FWHM). The blue-emitting quantum dots, In1-xGaxP@ZnS of outstanding quality (PLQY = 65 %, FWHM = 46 nm) is successfully synthesized with our new P and metal complex precursors. Furthermore, we apply those QDs to fabricate blue-emitting quantum dot light-emitting devices (QLEDs) with the external quantum efficiency of 0.20 % which is the best among the III-V-based blue-emitting QLEDs reported so far.
关键词： III-V semiconductors,Photoluminescence,Blue-emitting,QLEDs,Quantum dots
更新于2025-09-23 15:19:57
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Growth of InGaAs Solar Cells on InP(001) Miscut Substrates Using Solid‐Source Molecular Beam Epitaxy
摘要： Herein, the effects of both the growth temperature and the substrate miscut on the properties of lattice-matched InGaAs solar cells grown on InP substrates via solid-source molecular beam epitaxy are investigated. The growth temperature is varied from 420 to 490 (cid:1)C. InP(001) miscut by 2(cid:1) toward (111)A and (111)B denoted by 2(cid:1)A and 2(cid:1)B, respectively, and exactly-cut substrates are used. Material quality is evaluated by photoluminescence (PL) and atomic force microscopy (AFM) measurements. At room temperature, the PL emissions become more intense at higher growth temperatures and with miscut substrates, indicating less nonradiative recombination. AFM results show a streaky surface with step structures along the ?1ˉ10(cid:4) direction for cell grown at 490 (cid:1)C on 2(cid:1)A, suggesting that the substrate promotes step-?ow growth. Consequently, the highest conversion ef?ciency (12.3%) for the cell grown at 490 (cid:1)C on 2(cid:1)A is obtained. Especially, the open-circuit voltage (VOC) increases from the baseline of 0.350 V (for the cell grown at 420 (cid:1)C on an exact substrate) to 0.374 V. The Eg(cid:3)VOC de?cit, where W oc, of 369 mV is obtained, which is a standard benchmark for high-material-quality solar cells.
关键词： III–V semiconductors,molecular beam epitaxy,solar cells
更新于2025-09-19 17:13:59
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Effect of the Irradiation on Optical and Electrical Properties of Triple-Junction Flexible Thin Solar Cells for Space Applications
摘要： The most common multi-junction solar cell arrangement employs the InGaP/InGaAs/Ge configuration, which is usually exploited for high-efficiency space applications. We here test the reliability of a triple-junction device with an innovative low-thickness and flexible configuration: this is investigation is aimed at providing its main macroscopic features which must be taken into account for their applications. Notably, the specific optical and electrical features and the performance variation of these thin solar cells are systematically analyzed, both in begin-of-life (BOL) configuration and after irradiation (end-of-life, EOL) by either electrons or protons. Measurements of I – V curves, with correlated parameters, and of spectral responses (external quantum efficiency) are accomplished on several BOL and EOL samples: this allows to describe the inhomogeneous damage of the subjunctions and to follow the evolution of the solar cell physical quantities as a function of the kind and the amount of irradiation. Finally, photoluminescence emission spectra are measured, pointing out the effect of particle bombardment on luminescent features. Our results show that these innovative solar devices allow for the combination of high specific power, mechanical flexibility, high performance, and strong resistance to particle irradiation, making them an excellent option for space applications.
关键词： multi-junction cells,III-V semiconductors,component cells,irradiated cells,space solar cells
更新于2025-09-16 10:30:52
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Device characteristics and material developments of indoor photovoltaic devices
摘要： Indoor photovoltaics (IPVs), which convert the indoor light energy into direct electricity, have attracted research attention due to their potential use as an excellent amicable solution of sustainable power source to drive low-power-needed sensors for the internet of things (IoT) applications. Our daily life adopts various indoor light sources, such as indirect sunlight, incandescent lamps, halogen lamps, ?uorescent lamps, and LED bulbs, that typically deliver lower light intensity (200–1000 lux) as compared to that of sun light (～100,000 lx). In this review, we ?rstly classi?ed the indoor lights depending on their working mechanism and resulting emission spectrum. Because the indoor light intensities are rather low that may lead to overestimate/underestimate the power conversion e?ciency (PCE) of IPV devices, then, the cautious points for correctly measuring the indoor light intensity as well as the device characteristics are summarized. Several light sources with various light intensities are reported so far, but for lack of common or standard calibration meter that induces a ambiguity in PCE determination, so we suggest/propose to use a universal LED lux meter with NIST-traceable calibration (e.g. Extech LT40-NIST) and also recommended the device results are expressed in maximum power point Pmax along with PCE values. It is generally believed that the materials play key roles on the performance of the IPV devices. Since the indoor light intensity is much weaker as compared to that of outdoor irradiation, the typical inferior photo-stability of organic materials under sunlight may not be as crucial as we considered to harvest indoor light energy, opening a great room for organic IPV material developments. In principle, all materials for outdoor PVs may also be useful for IPVs, but the fundamental material requirement for IPVs which needs su?ciently covering the absorption range between the 350–700 nm with high molar extinction coe?cient should be primarily concerned. In order to get the thorough knowledge of materials for achieving better e?cient IPVs, the reported IPVs were collected and summarized. According to these reports, the materials utilized for IPVs have been classi?ed into two major groups, inorganic and organic materials, then divided them into several sub-classes, including (1) silicon and III-V semiconductor photovoltaics, (2) dye-sensitized photovoltaics, (3) organic photovoltaics, and (4) perovskite-based photovoltaics, depend on their structural nature and device working principle. For every individual class, the structure-property-e?ciency relationship of the materials was analyzed together with the highlights on the best e?ciency material, challenge and perspective. For inorganic IPV materials, III-V semiconductor GaAs-based IPVs performed a very impressive PCE (28%). For dye sensitizers, there are more ?exible strategies to modulate the absorption pro?les of organic materials. A high e?ciency dye-sensitized solar cell (DSSC)-based IPV with a PCE up to 32% has been successfully realized with co-sensitized dyes. For organic solar cell (OSC)-based IPVs, fullerene-based acceptors are advantageous for their well-matching desired absorption range and superior electron transport features. A recent OSC-based IPV with the active layer composed of dithienobenzene-based donor and fullerene acceptor was reported to deliver a PCE of 28%. Among these emerging photovoltaic materials, it is no doubt that perovskites (e.g. CH3NH3PbI3) are superior for solar energy conversion due to the crystallinity for good charge transport, better spectral coverage and the low exciton binding energy. Until very recent, a perovskite-based IPV with a PCE of 35% was reported with good stability by the incorporation of an ionic liquid for e?ectively passivating the surface of the perovskite ?lm, indicating the bright prospect of perovskite for IPV application. Overall, the review on these reports implies the essential criteria of materials suitable for IPVs that may trigger new ideas for developing future champion materials for various devices and the realization of practical IPV applications.
关键词： Organic solar cells,Dye-sensitized solar cells,Silicon and III-V semiconductors,Perovskite materials,Power conversion efficiency,Internet of Things,Organic materials,Indoor photovoltaics
更新于2025-09-16 10:30:52
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Gallium Phosphide Solar Cell Structures with Improved Quantum Efficiencies
摘要： Gallium phosphide (GaP) solar cell structures with improved quantum efficiencies were realized using a modified liquid phase epitaxy (LPE) technique and diodes formed using semi-transparent Schottky contacts. The improvement is due to the addition of a small amount of aluminum to the gallium and phosphorus containing LPE melt. The Al reduces the background concentration of oxygen in the melt, which is known to produce deep trap states in GaP. Additionally, it was found that by depositing an aluminum (Al)-rich AlGaP layer on top of the active GaP and then selectively etching it away, the surface morphology of the active layer was significantly improved. Thus, the modified LPE technique eliminates the major problem of meniscus lines associated with the standard LPE method.
关键词： gallium phosphide,III–V semiconductors,Liquid phase epitaxy (LPE)
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optically Driven Attosecond Electron Dynamics in III-V Semiconductors
摘要： A fundamental understanding of ultrafast electron dynamics in solids induced by light is of great interest for future high-speed electro-optical devices operating in the petahertz frequency regime. In the last years, a number of publications demonstrated the possibility to resolve and control carrier dynamics in semiconductors and dielectrics on the few- to sub-femtosecond time scale using attosecond transient absorption spectroscopy (ATAS). These experiments were performed with a non-resonant pump pulse, i.e. pump photon energies smaller than the corresponding band gap. Here in contrast, we resolve for the first time the attosecond carrier dynamics induced by a resonant intense laser pulse. We study the attosecond electronic response in gallium arsenide (GaAs), a technologically important narrow band gap semiconductor.
关键词： gallium arsenide,III-V semiconductors,attosecond transient absorption spectroscopy,ultrafast electron dynamics,attosecond electron dynamics
更新于2025-09-11 14:15:04
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Dot size variability induced changes in the optical absorption spectra of interdiffused quantum dot systems
摘要： In this work, we have quantified the effects of dot size variability on the interband optical absorption spectra of interdiffused III–V quantum dot (QD) systems through analytical models which agree well with experimental data. The variability function induced due to inhomogeneous nature of dot size distribution has been considered to be Gaussian in nature, where individual dots have been assumed to be lens-shaped having inhomogeneous material composition inside the dot. This is necessary to consider any realistic interdiffused system. Such an assumption is not in line-up with the conventional methodologies reported earlier on the subject, where the QD composition was considered to be homogeneous, presenting an ideal or quasi-ideal situation which may be applicable only for dot structures in absence of interdiffusion. Moreover, for the first time, the effects of dot size variability and interdiffusion on the optical spectra of QD systems have been analysed in the same platform. The effects of dot size deviation, QD aspect ratio, core group III content inside the dot, standard deviation, and so on, on the optical absorption spectra have been demonstrated.
关键词： Dot size variability,III–V semiconductors,Optical absorption spectra,Interdiffusion,Quantum dots
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Model Calibration of InGaAs/InP p-I-n Test Structures
摘要： Numerical calibration of InGaAs/InP double-heterostructure p-I-n junctions is performed at room temperature using guarded test structures of various areas and investigating the contributions from minority carrier diffusion, depletion region generation and finally perimeter (shunt) leakage. The perimeter leakage is determined to be 0.5 pA/cm, whereas the depletion region contributes 2.2 nA/cm2; the bulk diffusion contribution is excluded via the guard ring but can be computed analytically to be 2.0 nA/cm2. Reproducing the experimental test structures within the numerical modeling environment accurately reproduces the data based on calibrating the diffusion length and SRH lifetime.
关键词： dark current,III-V semiconductors,diffusion length,perimeter leakage,recombination
更新于2025-09-11 14:15:04