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Wang Z, Lu D, Kondamareddy KK, He Y, Gu W, Li J, Fan H, Wang H, Ho W. Recent Advances and Insights in Designing Zn xCd 1-xS-Based Photocatalysts for Hydrogen Production and Synergistic Selective Oxidation to Value-Added Chemical Production. ACS APPLIED MATERIALS & INTERFACES 2024; 16:48895-48926. [PMID: 39235068 DOI: 10.1021/acsami.4c09599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/06/2024]
Abstract
Combining the hydrogen (H2) extraction process and organic oxidation synthesis in photooxidation-reduction reactions mediated by semiconductors is a desirable strategy because rich chemicals are evolved as byproducts along with hydrogen in trifling conditions upon irradiation, which is the only effort. The bifunctional photocatalytic strategy facilitates the feasible formation of a C═O/C─C bond from a large number of compounds containing a X-H (X = C, O) bond; therefore, the production of H2 can be easily realized without support from third agents like chemical substances, thus providing an eco-friendly and appealing organic synthesis strategy. Among the widely studied semiconductor nanomaterials, ZnxCd1-xS has been continuously studied and explored by researchers over the years, and it has attracted much consideration owing to its unique advantages such as adjustable band edge position, rich elemental composition, excellent photoelectric properties, and ability to respond to visible light. Therefore, nanostructures based on ZnxCd1-xS have been widely studied as a feasible way to efficiently prepare hydrogen energy and selectively oxidize it into high-value fine chemicals. In this Review, first, the crystal and energy band structures of ZnxCd1-xS, the model of twin nanocrystals, the photogenerated charge separation mechanism of the ZB-WZ-ZB homojunction with crisscross bands, and the Volmer-Weber growth mechanism of ZnxCd1-xS are described. Second, the morphology, structure, modification, synthesis, and vacancy engineering of ZnxCd1-xS are surveyed, summarized, and discussed. Then, the research progress in ZnxCd1-xS-based photocatalysis in photocatalytic hydrogen extraction (PHE) technology, the mechanism of PHE, organic substance (benzyl alcohol, methanol, etc.) dehydrogenation, the factors affecting the efficiency of photocatalytic discerning oxidation of organic derivatives, and selective C-H activation and C-C coupling for synergistic efficient dehydrogenation of photocatalysts are described. Conclusively, the challenges in the applicability of ZnxCd1-xS-based photocatalysts are addressed for further research development along this line.
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Affiliation(s)
- Zhennan Wang
- School of Science, Xi'an Polytechnic University, No.19 of Jinhua South Road, Beilin District, Xi'an 710048, P. R. China
| | - Dingze Lu
- School of Science, Xi'an Polytechnic University, No.19 of Jinhua South Road, Beilin District, Xi'an 710048, P. R. China
- Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, New Territories, Hong Kong 999077, P. R. China
- State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Kiran Kumar Kondamareddy
- School of Pure Science, College of Engineering and Technical Vocational Education and Training (CETVET), Fiji National University, Lautoka, Fiji
| | - Yang He
- School of Science, Xi'an Polytechnic University, No.19 of Jinhua South Road, Beilin District, Xi'an 710048, P. R. China
| | - Wenju Gu
- School of Science, Xi'an Polytechnic University, No.19 of Jinhua South Road, Beilin District, Xi'an 710048, P. R. China
| | - Jing Li
- School of Science, Xi'an Polytechnic University, No.19 of Jinhua South Road, Beilin District, Xi'an 710048, P. R. China
| | - Huiqing Fan
- State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Hongmei Wang
- College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, Zhejiang 314001, China
| | - Wingkei Ho
- Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, New Territories, Hong Kong 999077, P. R. China
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Alkhazraji E, Chow WW, Grillot F, Bowers JE, Wan Y. Linewidth narrowing in self-injection-locked on-chip lasers. LIGHT, SCIENCE & APPLICATIONS 2023; 12:162. [PMID: 37380663 DOI: 10.1038/s41377-023-01172-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 04/25/2023] [Accepted: 04/26/2023] [Indexed: 06/30/2023]
Abstract
Stable laser emission with narrow linewidth is of critical importance in many applications, including coherent communications, LIDAR, and remote sensing. In this work, the physics underlying spectral narrowing of self-injection-locked on-chip lasers to Hz-level lasing linewidth is investigated using a composite-cavity structure. Heterogeneously integrated III-V/SiN lasers operating with quantum-dot and quantum-well active regions are analyzed with a focus on the effects of carrier quantum confinement. The intrinsic differences are associated with gain saturation and carrier-induced refractive index, which are directly connected with 0- and 2-dimensional carrier densities of states. Results from parametric studies are presented for tradeoffs involved with tailoring the linewidth, output power, and injection current for different device configurations. Though both quantum-well and quantum-dot devices show similar linewidth-narrowing capabilities, the former emits at a higher optical power in the self-injection-locked state, while the latter is more energy-efficient. Lastly, a multi-objective optimization analysis is provided to optimize the operation and design parameters. For the quantum-well laser, minimizing the number of quantum-well layers is found to decrease the threshold current without significantly reducing the output power. For the quantum-dot laser, increasing the quantum-dot layers or density in each layer increases the output power without significantly increasing the threshold current. These findings serve to guide more detailed parametric studies to produce timely results for engineering design.
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Affiliation(s)
- Emad Alkhazraji
- Integrated Photonics Lab, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
| | - Weng W Chow
- Sandia National Laboratories, Albuquerque, NM, 87185-1086, USA.
| | - Frédéric Grillot
- LTCI, Télécom Paris, Institut Polytechnique de Paris, 91120, Palaiseau, France
| | - John E Bowers
- Department of Electronic and Computer Engineering, University of California - Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Yating Wan
- Integrated Photonics Lab, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia.
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Ming M, Gao F, Wang JH, Zhang JY, Wang T, Yao Y, Hu H, Zhang JJ. Strain-induced ordered Ge(Si) hut wires on patterned Si (001) substrates. NANOSCALE 2023; 15:7311-7317. [PMID: 37013680 DOI: 10.1039/d2nr05238e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Ge/Si nanowires are predicted to be a promising platform for spin and even topological qubits. While for large-scale integration of these devices, nanowires with fully controlled positions and arrangements are a prerequisite. Here, we have reported ordered Ge hut wires by multilayer heteroepitaxy on patterned Si (001) substrates. Self-assembled GeSi hut wire arrays are orderly grown inside patterned trenches with post growth surface flatness. Such embedded GeSi wires induce tensile strain on the Si surface, which results in preferential nucleation of Ge nanostructures. Ordered Ge nano-dashes, disconnected wires and continuous wires are obtained correspondingly by tuning the growth conditions. These site-controlled Ge nanowires on a flattened surface lead to the ease of fabrication and large-scale integration of nanowire quantum devices.
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Affiliation(s)
- Ming Ming
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
- College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
- Hefei National Laboratory, Hefei 230088, China
| | - Fei Gao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
- Qilu Institute of Technology, Jinan 250200, China
| | - Jian-Huan Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
- Hefei National Laboratory, Hefei 230088, China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
| | - Jie-Yin Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
- Hefei National Laboratory, Hefei 230088, China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
| | - Ting Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
- Hefei National Laboratory, Hefei 230088, China
- Songshan Lake Materials Laboratory, Dongguan 523808, China
| | - Yuan Yao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
| | - Hao Hu
- Hefei National Laboratory, Hefei 230088, China
- Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710054, China
| | - Jian-Jun Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
- College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
- Hefei National Laboratory, Hefei 230088, China
- Songshan Lake Materials Laboratory, Dongguan 523808, China
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Chen P, Zhang N, Peng K, Zhang L, Yan J, Jiang Z, Zhong Z. Artificial Graphene on Si Substrates: Fabrication and Transport Characteristics. ACS NANO 2021; 15:13703-13711. [PMID: 34286957 DOI: 10.1021/acsnano.1c04995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Artificial graphene (AG) based on a honeycomb lattice of semiconductor quantum dots (QDs) has been of great interest for exploration and applications of massless Dirac Fermions in semiconductors thanks to the tunable interplay between the carrier interactions and the honeycomb topology. Here, an innovative strategy to realize AG on Si substrates is developed by fabricating a honeycomb lattice of Au nanodisks on a Si/GeSi quantum well. The lateral potential modulation induced by the nanoscale Au/Si Schottky junction results in the formation of quantum dots arranged in a honeycomb lattice to form AG. Nonlinear current-voltage curves of the AG reveal conductance phase transitions with switch on/off voltages, a large electric hysteresis loop, and a strong sharp current peak accompanied by a group of differential-conductance peaks and negative differential conductance around the switch-on voltage, which can be modulated by temperature and light. These features are interpreted by a model based on the Coulomb blockade effect, the collective resonant tunneling, and the coupling of holes in the AG. Our results not only demonstrate an approach to the formation but also will greatly stimulate the characterizations and the applications of innovative semiconductor-based AG.
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Affiliation(s)
- Peizong Chen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Ningning Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Kun Peng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Lijian Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Jia Yan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Zuimin Jiang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Zhenyang Zhong
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
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Brehm M, Grydlik M. Site-controlled and advanced epitaxial Ge/Si quantum dots: fabrication, properties, and applications. NANOTECHNOLOGY 2017; 28:392001. [PMID: 28729522 DOI: 10.1088/1361-6528/aa8143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In this review, we report on fabrication paths, challenges, and emerging solutions to integrate group-IV epitaxial quantum dots (QDs) as active light emitters into the existing standard Si technology. Their potential as laser gain material for the use of optical intra- and inter-chip interconnects as well as possibilities to combine a single-photon-source-based quantum cryptographic means with Si technology will be discussed. We propose that the mandatory addressability of the light emitters can be achieved by a combination of organized QD growth assisted by templated self-assembly, and advanced inter-QD defect engineering to boost the optical emissivity of group-IV QDs at room-temperature. Those two main parts, the site-controlled growth and the light emission enhancement in QDs through the introduction of single defects build the main body of the review. This leads us to a roadmap for the necessary further development of this emerging field of CMOS-compatible group-IV QD light emitters for on-chip applications.
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Quantitative strain analysis of InAs/GaAs quantum dot materials. Sci Rep 2017; 7:45376. [PMID: 28349927 PMCID: PMC5368971 DOI: 10.1038/srep45376] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 02/22/2017] [Indexed: 11/12/2022] Open
Abstract
Geometric phase analysis has been applied to high resolution aberration corrected (scanning) transmission electron microscopy images of InAs/GaAs quantum dot (QD) materials. We show quantitatively how the lattice mismatch induced strain varies on the atomic scale and tetragonally distorts the lattice in a wide region that extends several nm into the GaAs spacer layer below and above the QDs. Finally, we show how V-shaped dislocations originating at the QD/GaAs interface efficiently remove most of the lattice mismatch induced tetragonal distortions in and around the QD.
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López-Vidrier J, Berencén Y, Hernández S, Mundet B, Gutsch S, Laube J, Hiller D, Löper P, Schnabel M, Janz S, Zacharias M, Garrido B. Structural parameters effect on the electrical and electroluminescence properties of silicon nanocrystals/SiO2 superlattices. NANOTECHNOLOGY 2015; 26:185704. [PMID: 25872562 DOI: 10.1088/0957-4484/26/18/185704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effect of the oxide barrier thickness (tSiO2) reduction and the Si excess ([Si]exc) increase on the electrical and electroluminescence (EL) properties of Si-rich oxynitride (SRON)/SiO2 superlattices (SLs) is investigated. The active layers of the metal-oxide-semiconductor devices were fabricated by alternated deposition of SRON and SiO2 layers on top of a Si substrate. The precipitation of the Si excess and thus formation of Si nanocrystals (NCs) within the SRON layers was achieved after an annealing treatment at 1150 °C. A structural characterization revealed a high crystalline quality of the SLs for all devices, and the evaluated NC crystalline size is in agreement with a good deposition and annealing control. We found a dramatic conductivity enhancement when the Si content is increased or the SiO2 barrier thickness is decreased, due to a larger interaction of the carrier wavefunctions from adjacent layers. EL recombination dynamics were studied, revealing radiative recombination decay times of the order of tens of microseconds. Lower lifetimes were found at higher [Si]exc, attributed to exciton confinement delocalization, whereas intermediate barrier thicknesses present the slowest decay. The electrical-to-light conversion efficiency increases monotonously at thicker barriers and smaller Si contents. We ascribe these effects mainly to free carriers, which enhance carrier transport through the SLs while strongly quenching light emission. Finally, the combination of the different results led us to conclude that tSiO2 ∼ 2 nm and [Si]exc from 12 to 15 at% are the ideal structure parameters for a balanced electro-optical response of Si NC-based SLs.
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Affiliation(s)
- J López-Vidrier
- MIND-IN2UB, Electronics Department, University of Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain
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8
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Park JH, Mandal A, Um DY, Kang S, Lee DS, Lee CR. Fabrication of InxGa1−xN/GaN QDs with InAlGaN capping layer by coaxial growth on non-(semi-) polar n-GaN NWs using metal organic chemical vapor deposition for blue emission. RSC Adv 2015. [DOI: 10.1039/c5ra06836c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Merits of InAlGaN capping layer over self-assembled InxGa1−xN/GaN quantum dots coaxially grown on n-GaN nanowires using MOCVD.
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Affiliation(s)
- Ji-Hyeon Park
- Semiconductor Materials Process Laboratory
- School of Advanced Materials Engineering
- Engineering College
- Research Center for Advanced Materials Development (RCAMD)
- Chonbuk National University
| | - Arjun Mandal
- Semiconductor Materials Process Laboratory
- School of Advanced Materials Engineering
- Engineering College
- Research Center for Advanced Materials Development (RCAMD)
- Chonbuk National University
| | - Dae-Young Um
- Semiconductor Materials Process Laboratory
- School of Advanced Materials Engineering
- Engineering College
- Research Center for Advanced Materials Development (RCAMD)
- Chonbuk National University
| | - San Kang
- Semiconductor Materials Process Laboratory
- School of Advanced Materials Engineering
- Engineering College
- Research Center for Advanced Materials Development (RCAMD)
- Chonbuk National University
| | - Da-som Lee
- Semiconductor Materials Process Laboratory
- School of Advanced Materials Engineering
- Engineering College
- Research Center for Advanced Materials Development (RCAMD)
- Chonbuk National University
| | - Cheul-Ro Lee
- Semiconductor Materials Process Laboratory
- School of Advanced Materials Engineering
- Engineering College
- Research Center for Advanced Materials Development (RCAMD)
- Chonbuk National University
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Liu WS, Chu TF, Huang TH. Energy band structure tailoring of vertically aligned InAs/GaAsSb quantum dot structure for intermediate-band solar cell application by thermal annealing process. OPTICS EXPRESS 2014; 22:30963-30974. [PMID: 25607045 DOI: 10.1364/oe.22.030963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This study presents an band-alignment tailoring of a vertically aligned InAs/GaAs(Sb) quantum dot (QD) structure and the extension of the carrier lifetime therein by rapid thermal annealing (RTA). Arrhenius analysis indicates a larger activation energy and thermal stability that results from the suppression of In-Ga intermixing and preservation of the QD heterostructure in an annealed vertically aligned InAs/GaAsSb QD structure. Power-dependent and time-resolved photoluminescence were utilized to demonstrate the extended carrier lifetime from 4.7 to 9.4 ns and elucidate the mechanisms of the antimony aggregation resulting in a band-alignment tailoring from straddling to staggered gap after the RTA process. The significant extension in the carrier lifetime of the columnar InAs/GaAsSb dot structure make the great potential in improving QD intermediate-band solar cell application.
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Simmonds PJ, Sun M, Laghumavarapu RB, Liang B, Norman AG, Luo JW, Huffaker DL. Improved quantum dot stacking for intermediate band solar cells using strain compensation. NANOTECHNOLOGY 2014; 25:445402. [PMID: 25319397 DOI: 10.1088/0957-4484/25/44/445402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We use thin tensile-strained AlAs layers to manage compressive strain in stacked layers of InAs/AlAsSb quantum dots (QDs). The AlAs layers allow us to reduce residual strain in the QD stacks, suppressing strain-related defects. AlAs layers 2.4 monolayers thick are sufficient to balance the strain in the structures studied, in agreement with theory. Strain balancing improves material quality and helps increase QD uniformity by preventing strain accumulation and ensuring that each layer of InAs experiences the same strain. Stacks of 30 layers of strain-balanced QDs exhibit carrier lifetimes as long as 9.7 ns. QD uniformity is further enhanced by vertical ABAB… ordering of the dots in successive layers. Strain compensated InAs/AlAsSb QD stacks show great promise for intermediate band solar cell applications.
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Affiliation(s)
- Paul J Simmonds
- California NanoSystems Institute, UCLA, Los Angeles, CA 90095, USA
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11
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Abstract
Imaging object details with length scales below approximately 200 nm has been historically difficult for conventional microscope objective lenses because of their inability to resolve features smaller than one-half the optical wavelength. Here we review some of the recent approaches to surpass this limit by harnessing self-assembly as a fabrication mechanism. Self-assembly can be used to form individual nano- and micro-lenses, as well as to form extended arrays of such lenses. These lenses have been shown to enable imaging with resolutions as small as 50 nm half-pitch using visible light, which is well below the Abbe diffraction limit. Furthermore, self-assembled nano-lenses can be used to boost contrast and signal levels from small nano-particles, enabling them to be detected relative to background noise. Finally, alternative nano-imaging applications of self-assembly are discussed, including three-dimensional imaging, enhanced coupling from light-emitting diodes, and the fabrication of contrast agents such as quantum dots and nanoparticles.
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12
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Ogata T, Hirakawa N, Nakashima Y, Kuwahara Y, Kurihara S. Fabrication of polymer/ZnS nanoparticle composites by matrix-mediated synthesis. REACT FUNCT POLYM 2014. [DOI: 10.1016/j.reactfunctpolym.2014.03.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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13
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Sonnenberg D, Küster A, Graf A, Heyn C, Hansen W. Vertically stacked quantum dot pairs fabricated by nanohole filling. NANOTECHNOLOGY 2014; 25:215602. [PMID: 24784358 DOI: 10.1088/0957-4484/25/21/215602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Strain-free, vertically coupled GaAs quantum dots (QDs) with an ultra-low density below 1 × 10(7) cm(-2) are fabricated by filling of self-assembled nanoholes with a GaAs/AlGaAs/GaAs layer sequence. The sizes of the two QDs, forming a QD pair (QDP), as well as the AlGaAs tunnel-barrier between the dots are tuned independently. We present atomic force microscopy studies of the QDP formation steps. We have performed photoluminescence studies of single QDPs with varied dot size and tunnel-barrier thickness. The data indicate non-resonant tunnelling between the dots. Furthermore, we apply the quantum confined Stark effect to tune the photoluminescence energy by up to 25 meV.
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Affiliation(s)
- D Sonnenberg
- Institute of Applied Physics, University of Hamburg, D-20355 Hamburg, Germany
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14
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Ma Y, Zhong Z, Lv Q, Qiu W, Wang X, Zhou T, Fan Y, Jiang Z. Optical properties of coupled three-dimensional Ge quantum dot crystals. OPTICS EXPRESS 2013; 21:6053-6060. [PMID: 23482173 DOI: 10.1364/oe.21.006053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on optical properties of coupled three-dimensional (3D) Ge quantum dot crystals (QDCs). With increasing the vertical periodic number of the QDCs, the photoluminescence (PL) spectral linewidth decreased exponentially, and so did the peak energy blueshift caused by increasing excitation power, which are attributed to the electronic coupling and thus the formation of miniband. In the PL spectra, the relative intensity of the transverse-optical (TO) phonon replica also decreases with increasing the vertical periodic number, which is attributed to the increased Brillouin-zone folding effect in vertical direction and therewith the relaxation of indirect transition nature of exciton recombination. Besides, the optical reflectivity at the interband transition energy was much more reduced for the QDCs than for the in-plane disordered QDs grown with the same parameters, indicating a higher interband absorption of the QDCs due to the miniband formation.
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Affiliation(s)
- Yingjie Ma
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures Ministry of Education and Department of Physics, Fudan University, Shanghai 200433, China
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15
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Lin A, Liang BL, Dorogan VG, Mazur YI, Tarasov GG, Salamo GJ, Huffaker DL. Strong passivation effects on the properties of an InAs surface quantum dot hybrid structure. NANOTECHNOLOGY 2013; 24:075701. [PMID: 23358560 DOI: 10.1088/0957-4484/24/7/075701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on an InAs quantum dot (QD) hybrid structure with a top surface QD layer coupled to two buried QD layers that is highly sensitive to surface passivation. After 180 min of passivation, the photoluminescence (PL) peak of the surface QDs shifts from 1545 to 1275 nm while its intensity decreases by one order of magnitude. Time-resolved PL reveals a significant decrease of carrier tunneling between the QD layers because of the surface state modification by chemical treatment. A simple model with rate equations is used to explain the observed optical performance. Our results show that the optical performance of this hybrid structure is very sensitive to the surface environment, making it a potential candidate for sensing applications.
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Affiliation(s)
- A Lin
- California NanoSystems Institute and Electrical Engineering Department, University of California at Los Angeles, CA 90095, USA
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16
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Ma YJ, Zhong Z, Yang XJ, Fan YL, Jiang ZM. Factors influencing epitaxial growth of three-dimensional Ge quantum dot crystals on pit-patterned Si substrate. NANOTECHNOLOGY 2013; 24:015304. [PMID: 23220787 DOI: 10.1088/0957-4484/24/1/015304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigated the molecular beam epitaxy growth of three-dimensional (3D) Ge quantum dot crystals (QDCs) on periodically pit-patterned Si substrates. A series of factors influencing the growth of QDCs were investigated in detail and the optimized growth conditions were found. The growth of the Si buffer layer and the first quantum dot (QD) layer play a key role in the growth of QDCs. The pit facet inclination angle decreased with increasing buffer layer thickness, and its optimized value was found to be around 21°, ensuring that all the QDs in the first layer nucleate within the pits. A large Ge deposition amount in the first QD layer favors strain build-up by QDs, size uniformity of QDs and hence periodicity of the strain distribution; a thin Si spacer layer favors strain correlation along the growth direction; both effects contribute to the vertical ordering of the QDCs. Results obtained by atomic force microscopy and cross-sectional transmission electron microscopy showed that 3D ordering was achieved in the Ge QDCs with the highest ever areal dot density of 1.2 × 10(10) cm(-2), and that the lateral and the vertical interdot spacing were ~10 and ~2.5 nm, respectively.
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Affiliation(s)
- Y J Ma
- State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
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17
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BHATTACHARYA P, STIFF-ROBERTS AD, KRISHNA SANJAY, KENNERLY S. QUANTUM DOT INFRARED DETECTORS AND SOURCES. ACTA ACUST UNITED AC 2011. [DOI: 10.1142/s0129156402001885] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
InAs/GaAs quantum dot devices have the potential to be the leading technology for infrared detection and emission, which are necessary for many military and domestic applications. Quantum dot infrared photodetectors yield higher operating temperatures, lower dark currents, and more wavelength tunability. They also permit the detection of normal-incidence light. Quantum dot infrared sources are also expected to yield higher operating temperatures, in addition to lower threshold currents and higher modulation bandwidths. After a brief review of the history of infrared detection and emission, the optical and electrical characteristics of self-organized In(Ga)As/GaAs quantum dots grown by molecular beam epitaxy are discussed, followed by results for the quantum dot detectors and emitters that have been developed at the University of Michigan, Ann Arbor.
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Affiliation(s)
- P. BHATTACHARYA
- Solid State Electronics Laboratory, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109-2122, USA
| | - A. D. STIFF-ROBERTS
- Solid State Electronics Laboratory, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109-2122, USA
| | - SANJAY KRISHNA
- Center for High Technology Materials, Department of Electrical Engineering and Computer Engineering, University of New Mexico, Albuquerque, NM 87106, USA
| | - S. KENNERLY
- Sensors and Electron Devices Directorate, US Army Research Laboratory, Adelphi, Maryland 20783, USA
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18
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Kushwaha MS. Single-particle and collective excitations in quantum wires made up of vertically stacked quantum dots: zero magnetic field. J Chem Phys 2011; 135:124704. [PMID: 21974549 DOI: 10.1063/1.3640889] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report on the theoretical investigation of the elementary electronic excitations in a quantum wire made up of vertically stacked self-assembled InAs/GaAs quantum dots. The length scales (of a few nanometers) involved in the experimental setups prompt us to consider an infinitely periodic system of two-dimensionally confined (InAs) quantum dot layers separated by GaAs spacers. The resultant quantum wire is characterized by a two-dimensional harmonic confining potential in the x-y plane and a periodic (Kronig-Penney) potential along the z (or the growth) direction within the tight-binding approximation. Since the wells and barriers are formed from two different materials, we employ the Bastard's boundary conditions in order to determine the eigenfunctions along the z direction. These wave functions are then used to generate the Wannier functions, which, in turn, constitute the legitimate Bloch functions that govern the electron dynamics along the direction of periodicity. Thus, the Bloch functions and the Hermite functions together characterize the whole system. We then make use of the Bohm-Pines' (full) random-phase approximation in order to derive a general nonlocal, dynamic dielectric function. Thus, developed theoretical framework is then specified to work within a (lowest miniband and) two-subband model that enables us to scrutinize the single-particle as well as collective responses of the system. We compute and discuss the behavior of the eigenfunctions, band-widths, density of states, Fermi energy, single-particle and collective excitations, and finally size up the importance of studying the inverse dielectric function in relation with the quantum transport phenomena. It is remarkable to notice how the variation in the barrier- and well-widths can allow us to tailor the excitation spectrum in the desired energy range. Given the advantage of the vertically stacked quantum dots over the planar ones and the foreseen applications in the single-electron devices and in the quantum computation, it is quite interesting and important to explore the electronic, optical, and transport phenomena in such systems.
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Affiliation(s)
- Manvir S Kushwaha
- Department of Physics and Astronomy, Rice University, P.O. Box 1892, Houston, Texas 77251, USA.
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Schmidt KH, Medeiros-Ribeiro G, Cheng M, Petroff PM. Limits and Properties of Size Quantization Effects in InAs Self Assembled Quantum Dots. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-452-275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractIn this paper we report on the limits and properties of size quantization effects in InAs self assembled quantum dots (QDs). Size, density and character of the InAs islands are investigated by transmission electron microscopy. The electronic and optical properties of the islands in the coherent and dislocated growth regime are studied using capacitance, photoluminescence, photovoltage and photocurrent spectroscopy. In the data measured with the different techniques, the change in dot size and density as well as the transition from coherent to dislocated island growth is clearly observable. An increasing QD size causes a red shift in the energetic position of the QD features while the density of the islands is reflected in the intensity of the QD signal. The decrease in intensity at high InAs coverage is attributed to dislocated island formation.
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Iikawa F, Donchev V, Ivanov T, Dias GO, Tizei LHG, Lang R, Heredia E, Gomes PF, Brasil MJSP, Cotta MA, Ugarte D, Martinez Pastor JP, de Lima MM, Cantarero A. Spatial carrier distribution in InP/GaAs type II quantum dots and quantum posts. NANOTECHNOLOGY 2011; 22:065703. [PMID: 21212489 DOI: 10.1088/0957-4484/22/6/065703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.
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Affiliation(s)
- F Iikawa
- Instituto de Física Gleb Wataghin, Unicamp, Campinas-SP, Brazil.
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21
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Wang Y, Xiu F, Wang Y, Zou J, Beyermann WP, Zhou Y, Wang KL. Coherent magnetic semiconductor nanodot arrays. NANOSCALE RESEARCH LETTERS 2011; 6:134. [PMID: 21711627 PMCID: PMC3211181 DOI: 10.1186/1556-276x-6-134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 02/11/2011] [Indexed: 05/31/2023]
Abstract
In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors. Up to now, lack of reliable methods to obtain high-quality MnGe nanostructures with a desired shape and a good controllability has been a barrier to make these materials practically applicable for spintronic devices. Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility. Magnetotransport experiments reveal that the nanodot arrays possess giant magneto-resistance associated with geometrical effects. The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation.
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Affiliation(s)
- Yong Wang
- Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia Campus, Brisbane QLD 4072, Australia
- Electrical Engineering Department, University of California, Los Angeles, 56-125B Engineering IV Building, Los Angeles, CA, 90095, USA
| | - Faxian Xiu
- Electrical Engineering Department, University of California, Los Angeles, 56-125B Engineering IV Building, Los Angeles, CA, 90095, USA
| | - Ya Wang
- Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia Campus, Brisbane QLD 4072, Australia
| | - Jin Zou
- Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia Campus, Brisbane QLD 4072, Australia
| | - Ward P Beyermann
- Department of Physics, University of California-Riverside, 900 University Ave., Riverside, CA, 92521, USA
| | - Yi Zhou
- Electrical Engineering Department, University of California, Los Angeles, 56-125B Engineering IV Building, Los Angeles, CA, 90095, USA
| | - Kang L Wang
- Electrical Engineering Department, University of California, Los Angeles, 56-125B Engineering IV Building, Los Angeles, CA, 90095, USA
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22
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Hsu CC, Hsu RQ, Wu YH. Morphology and optical properties of single- and multi-layer InAs quantum dots. JOURNAL OF ELECTRON MICROSCOPY 2010; 59 Suppl 1:S149-S154. [PMID: 20576720 DOI: 10.1093/jmicro/dfq053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
An understanding of the structural and optical properties of quantum dots (QDs) is critical for their use in optical communication devices. In this study, single- and multi-layer self-organized InAs QDs grown on (001) GaAs substrates by molecular beam epitaxy (MBE) were investigated. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images show that the lateral size of multi-layer InAs QDs are larger and flatter than single-layer InAs QDs, which are oval-shaped. The change in shape and size may be attributed to the presence of InGaAs spacer layers in multi-layer InAs QDs. Reciprocal spacer mapping and fast Fourier transformation images clearly show that InGaAs spacer layers present in the multi-layer InAs QDs structures help to release the strain originally existing in the QDs. In addition, the photoluminescence peak of the multi-layer InAs QDs is broader than QD in the single-layer one, which implies that the multi-layer InAs QDs size variation is more random than the single-layer one and this corresponds with the HAADF-STEM images. These results prove that spacer layers release strain influencing the morphology and optical properties of the QDs.
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Affiliation(s)
- Chiung-Chih Hsu
- Department of Mechanical Engineering, National Chiao-Tung University, Hsinchu, Taiwan.
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23
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Yakes MK, Cress CD, Tischler JG, Bracker AS. Three-dimensional control of self-assembled quantum dot configurations. ACS NANO 2010; 4:3877-3882. [PMID: 20557120 DOI: 10.1021/nn100623q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We demonstrate techniques for growing three-dimensional quantum dot configurations using molecular beam epitaxy on faceted template islands. Molecular beam shadowing leads to new geometries through selective nucleation of the dots on the template edges. Strain-induced stacking converts the planar configurations into three-dimensional structures. The resulting dot morphologies and their configurational uniformity are studied using cross sectional scanning tunneling microscopy and atomic force microscopy. Combining photoluminescence measurements with structural characterization allows interpretation of the ensemble photoluminescence spectrum. Bright spectra for the three-dimensional structures suggest an improved method for combining lithographic nucleation sites with self-assembled dot growth. These techniques can be applied to lithographic templates to fabricate complex quantum dot networks.
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Affiliation(s)
- Michael K Yakes
- Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, D.C. 20375, USA
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24
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Wang ZM, Xie YZ, Kunets VP, Dorogan VG, Mazur YI, Salamo GJ. Multilayers of InGaAs Nanostructures Grown on GaAs(210) Substrates. NANOSCALE RESEARCH LETTERS 2010; 5:1320-1323. [PMID: 20676193 PMCID: PMC2897028 DOI: 10.1007/s11671-010-9645-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Accepted: 05/10/2010] [Indexed: 05/29/2023]
Abstract
Multilayers of InGaAs nanostructures are grown on GaAs(210) by molecular beam epitaxy. With reducing the thickness of GaAs interlayer spacer, a transition from InGaAs quantum dashes to arrow-like nanostructures is observed by atomic force microscopy. Photoluminescence measurements reveal all the samples of different spacers with good optical properties. By adjusting the InGaAs coverage, both one-dimensional and two-dimensional lateral ordering of InGaAs/GaAs(210) nanostructures are achieved.
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Affiliation(s)
- Zhiming M Wang
- Arkansas Institute for Nanoscale Materials Science and Engineering, University of Arkanssas, Fayetteville, AR, 72701, USA.
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25
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Flindt C, Sørensen AS, Lukin MD, Taylor JM. Spin-photon entangling diode. PHYSICAL REVIEW LETTERS 2007; 98:240501. [PMID: 17677949 DOI: 10.1103/physrevlett.98.240501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Indexed: 05/16/2023]
Abstract
We propose a semiconductor device that can electrically generate entangled electron spin-photon states, providing a building block for entanglement of distant spins. The device consists of a p-i-n diode structure that incorporates a coupled double quantum dot. We show that electronic control of the diode bias and local gating allow for the generation of single photons that are entangled with a robust quantum memory based on the electron spins. Practical performance of this approach to controlled spin-photon entanglement is analyzed.
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Affiliation(s)
- Christian Flindt
- MIC-Department of Micro and Nanotechnology, Technical University of Denmark, Kongens Lyngby 2800, Denmark
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26
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Chan CH, Huang YS, Wang JS, Tiong KK. Temperature dependence of surface photovoltage spectroscopy in vertically coupled self-organized InAs/GaAs quantum dots. OPTICS EXPRESS 2007; 15:1898-1906. [PMID: 19532428 DOI: 10.1364/oe.15.001898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The surface photovoltage (SPV) spectra of a series of vertically stacked self-organized InAs/GaAs quantum dot (QD)-based laser structures with different spacer layer (SL) thickness were obtained as a function of temperature (77 K </= T </= 300 K). A decrease of the compressive stress for thinner SL samples arising from coherent relaxation enables us to designate the effect of material intermixing as the most probable mechanism of the energetic blueshift of the observed structures. The turnaround characteristic of the temperature-dependent spectral intensity shows that the reduced SPV signal at higher temperature is limited by the carrier scattering and at lower temperature it is governed by the magnitude of built-in electric field and the escape efficiency of the photogenerated carriers. The dot states to be blueshifted by material intermixing are expected to have higher escape rate for carriers out of QDs, thus resulting in lower measurable temperature for the detected SPV signal. The relatively higher signal at low temperature for the 10 nm SL sample provides a direct evidence of the tunneling process of carriers in the stacked QD layers.
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27
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Talalaev VG, Cirlin GE, Tonkikh AA, Zakharov ND, Werner P, Gösele U, Tomm JW, Elsaesser T. Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices. NANOSCALE RESEARCH LETTERS 2006; 1:137. [PMCID: PMC3246673 DOI: 10.1007/s11671-006-9004-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The luminescence properties of highly strained, Sb-doped Ge/Si multi-layer heterostructures with incorporated Ge quantum dots (QDs) are studied. Calculations of the electronic band structure and luminescence measurements prove the existence of an electron miniband within the columns of the QDs. Miniband formation results in a conversion of the indirect to a quasi-direct excitons takes place. The optical transitions between electron states within the miniband and hole states within QDs are responsible for an intense luminescence in the 1.4–1.8 µm range, which is maintained up to room temperature. At 300 K, a light emitting diode based on such Ge/Si QD superlattices demonstrates an external quantum efficiency of 0.04% at a wavelength of 1.55 µm.
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Affiliation(s)
- VG Talalaev
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle/Saale, Germany
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany
- V.A. Fock Institute of Physics, St. Petersburg State University, Ulyanovskaya 1, 198504 Petrodvorets, St. Petersburg, Russia
| | - GE Cirlin
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle/Saale, Germany
- Ioffe Physico-Technical Institute RAS, 194021, Polytekhnicheskaya 26, St. Petersburg, Russia
| | - AA Tonkikh
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle/Saale, Germany
- Ioffe Physico-Technical Institute RAS, 194021, Polytekhnicheskaya 26, St. Petersburg, Russia
| | - ND Zakharov
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle/Saale, Germany
| | - P Werner
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle/Saale, Germany
| | - U Gösele
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle/Saale, Germany
| | - JW Tomm
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany
| | - T Elsaesser
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany
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28
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Henini M. Properties and applications of quantum dot heterostructures grown by molecular beam epitaxy. NANOSCALE RESEARCH LETTERS 2006; 1:32. [PMCID: PMC3246631 DOI: 10.1007/s11671-006-9017-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
One of the main directions of contemporary semiconductor physics is the production and study of structures with a dimension less than two: quantum wires and quantum dots, in order to realize novel devices that make use of low-dimensional confinement effects. One of the promising fabrication methods is to use self-organized three-dimensional (3D) structures, such as 3D coherent islands, which are often formed during the initial stage of heteroepitaxial growth in lattice-mismatched systems. This article is intended to convey the flavour of the subject by focussing on the structural, optical and electronic properties and device applications of self-assembled quantum dots and to give an elementary introduction to some of the essential characteristics.
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Affiliation(s)
- M Henini
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
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29
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Makeev MA, Madhukar A. Calculation of vertical correlation probability in Ge/Si(001) shallow island quantum dot multilayer systems. NANO LETTERS 2006; 6:1279-83. [PMID: 16771594 DOI: 10.1021/nl0602600] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We investigate the behavior of the island vertical pairing probability in multilayer systems of Ge island quantum dots (QDs) in Si(001). By combining a simple kinetic rate model with our previously reported atomistic simulation results on the nature of the stress field from buried shallow Ge islands having {105}-oriented sidewalls, we derive an analytical expression for correlation probability as a function of the parameters characterizing the multi-QD systems. The approach is based upon continuum mechanochemical potential model, which allows one to introduce necessary elements of the kinetics of island formation in a simple way. We compare the model predictions with available experimental data and find that the model provides a satisfactory description of the coupling probability. The correlation probability behavior as a function of capping layer thickness, Ge island size, interisland distance, and Ge adatom diffusion length is investigated within the framework of the developed model.
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Affiliation(s)
- Maxim A Makeev
- Collaboratory for Advanced Computing and Simulations, Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242, USA.
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30
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Ilahi B, Sfaxi L, Hassen F, Salem B, Bremond G, Marty O, Bouzaiene L, Maaref H. Optimizing the spacer layer thickness of vertically stacked InAs/GaAs quantum dots. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2006. [DOI: 10.1016/j.msec.2005.10.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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31
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Stinaff EA, Scheibner M, Bracker AS, Ponomarev IV, Korenev VL, Ware ME, Doty MF, Reinecke TL, Gammon D. Optical Signatures of Coupled Quantum Dots. Science 2006; 311:636-9. [PMID: 16410487 DOI: 10.1126/science.1121189] [Citation(s) in RCA: 414] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.
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Affiliation(s)
- E A Stinaff
- Naval Research Laboratory, Washington, DC 20375, USA
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32
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Gutiérrez M, Hopkinson M, Liu H, Tartakovskii A, Herrera M, González D, García R. Critical barrier thickness for the formation of InGaAs/GaAs quantum dots. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2005. [DOI: 10.1016/j.msec.2005.06.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Affiliation(s)
- J. G. Díaz
- Departament de Ciències Experimentals, UJI, Box 224, E-12080 Castelló, Spain
| | - J. Planelles
- Departament de Ciències Experimentals, UJI, Box 224, E-12080 Castelló, Spain
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35
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Heidemeyer H, Denker U, Müller C, Schmidt OG. Morphology response to strain field interferences in stacks of highly ordered quantum dot arrays. PHYSICAL REVIEW LETTERS 2003; 91:196103. [PMID: 14611591 DOI: 10.1103/physrevlett.91.196103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2003] [Indexed: 05/24/2023]
Abstract
Twofold stacked InGaAs/GaAs quantum dot (QD) layers are grown on GaAs(001) substrates patterned with square arrays of shallow holes. We study the surface morphology of the second InGaAs QD layer as a function of pattern periodicity. Comparing our experimental results with a realistic simulation of the strain energy density E(str) distribution, we find that the second InGaAs QD layer sensitively responds to the lateral strain-field interferences generated by the buried periodic QD array. This response includes the well-known formation of vertically aligned QDs but also the occurrence of QDs on satellite strain energy density minima. Our calculations show that base size and shape as well as lateral orientation of both QD types are predefined by the E(str) distribution on the underlying surface.
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Affiliation(s)
- H Heidemeyer
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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36
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Ohshima T, Song HZ, Okada Y, Akahane K, Miyazawa T, Kawabe M, Yokoyama N. Precisely ordered quantum dot array formed using AFM lithography for all-optical electron spin quantum computers. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pssc.200303096] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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37
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38
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Three-dimensional site control of self-organized InAs quantum dots by in situ scanning tunneling probe-assisted nanolithography and molecular beam epitaxy. ACTA ACUST UNITED AC 2002. [DOI: 10.1116/1.1467662] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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39
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40
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Trallero-Herrero C, Trallero-Giner C, Ulloa SE, Perez-Alvarez R. Electronic states in a cylindrical quantum lens: quantum chaos for decreasing system symmetry. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 64:056237. [PMID: 11736084 DOI: 10.1103/physreve.64.056237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2001] [Revised: 07/16/2001] [Indexed: 05/23/2023]
Abstract
The eigenvalue problem in a cylindrical lens geometry is studied. Using a conformal mapping method, the shape of the boundary and the Hamiltonian for a free particle are reduced to those of a two-dimensional problem with circular symmetry. The wave functions are separated into two independent Hilbert subspaces due to the inherent symmetry of the problem. For small geometry deformations, the solutions are found by a specially designed perturbation approach. Comparisons between exact and perturbative solutions are made for different lens parameters. As the symmetry of the lens is reduced, the characteristics of the spectrum and the corresponding spatial properties of the wave functions are studied. Our results provide a family of billiard geometries in which the electronic level spectrum is well characterized. In analyzing the level spacing distribution of the spectrum, a strong deviation from the Poisson and Wigner limiting distributions is found as the boundary geometry changes. This intermediate distribution is indicative of a mixed phase space, also revealed explicitly in the classical Poincaré maps we present.
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Affiliation(s)
- C Trallero-Herrero
- Nuclear Physics Department, Higher Institute for Nuclear Science and Technologies, Avenida Salvador Allende y Luaces, Vedado, Havana, Cuba
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41
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Bayer M, Hawrylak P, Hinzer K, Fafard S, Korkusinski M, Wasilewski ZR, Stern O, Forchel A. Coupling and entangling of quantum states in quantum dot molecules. Science 2001; 291:451-3. [PMID: 11161192 DOI: 10.1126/science.291.5503.451] [Citation(s) in RCA: 708] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We demonstrate coupling and entangling of quantum states in a pair of vertically aligned, self-assembled quantum dots by studying the emission of an interacting electron-hole pair (exciton) in a single dot molecule as a function of the separation between the dots. An interaction-induced energy splitting of the exciton is observed that exceeds 30 millielectron volts for a dot layer separation of 4 nanometers. The results are interpreted by mapping the tunneling of a particle in a double dot to the problem of a single spin. The electron-hole complex is shown to be equivalent to entangled states of two interacting spins.
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Affiliation(s)
- M Bayer
- Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.
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43
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Springholz G, Pinczolits M, Mayer P, Holy V, Bauer G, Kang HH, Salamanca-Riba L. Tuning of vertical and lateral correlations in self-organized PbSe/Pb1-xEuxTe quantum dot superlattices. PHYSICAL REVIEW LETTERS 2000; 84:4669-4672. [PMID: 10990767 DOI: 10.1103/physrevlett.84.4669] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/1999] [Indexed: 05/23/2023]
Abstract
The tuning of lateral and vertical correlations in self-organized PbSe/Pb 1-xEu xTe quantum dot superlattices by changes in the spacer thicknesses is demonstrated and shown to be due to finite size effects in the dot-dot interactions. As a consequence, different dot arrangements such as vertically aligned dot columns or fcc stacking are obtained for a single material system without changes in growth conditions. The different dot superstructures are shown to exhibit a different scaling behavior of the lateral versus vertical dot separation, as well as a different evolution of dot sizes and shapes.
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Affiliation(s)
- G Springholz
- Institut fur Halbleiter- und Festkorperphysik, Johannes Kepler Universitat, A-4040 Linz, Austria
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Klotzkin D, Bhattacharya P. Bringing quantum dots up to speed [Breaking the phonon bottleneck with high-speed modulation of quantum-dot lasers]. ACTA ACUST UNITED AC 2000. [DOI: 10.1109/101.819177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Strain relaxation-induced modifications of the optical properties of self-assembled InAs quantum dot superlattices. ACTA ACUST UNITED AC 2000. [DOI: 10.1116/1.591411] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Krost A, Heinrichsdorff F, Bimberg D, Bläsing J, Darhuber A, Bauer G. X-ray analysis of Self-Organized InAs/InGaAs Quantum Dot Structure. CRYSTAL RESEARCH AND TECHNOLOGY 1999. [DOI: 10.1002/(sici)1521-4079(199901)34:1<89::aid-crat89>3.0.co;2-u] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ordering of In[sub x]Ga[sub 1−x]As quantum dots self-organized on GaAs(311)B substrates. ACTA ACUST UNITED AC 1999. [DOI: 10.1116/1.590750] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Springholz G, Holy V, Pinczolits M, Bauer G. Self-organized growth of three- dimensional quantum-Dot crystals with fcc-like stacking and a tunable lattice constant. Science 1998; 282:734-7. [PMID: 9784129 DOI: 10.1126/science.282.5389.734] [Citation(s) in RCA: 416] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The self-organization of pyramidal PbSe islands that spontaneously form during strained-layer epitaxial growth of PbSe/Pb1-xEuxTe (x = 0.05 to 0.1) superlattices results in the formation of three-dimensional quantum-dot crystals. In these crystals, the dots are arranged in a trigonal lattice with a face-centered cubic (fcc)-like A-B-C-A-B-C vertical stacking sequence. The lattice constant of the dot crystal can be tuned continuously by changing the superlattice period. As shown by theoretical calculations, the elastic anisotropy in these artificial dot crystals acts in a manner similar to that of the directed chemical bonds of crystalline solids. The narrow size distribution and excellent control of the dot arrangement may be advantageous for optoelectronic device applications.
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Affiliation(s)
- G Springholz
- G. Springholz, M. Pinczolits, G. Bauer, Institut fur Halbleiterphysik, Johannes Kepler Universitat Linz, 4040 Linz, Austria. V. Holy, Laboratory of Thin Films and Nanostructures, Faculty of Science, Masaryk University, Kotlar
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Schmidt KH, Medeiros-Ribeiro G, Oestreich M, Petroff PM, Döhler GH. Carrier relaxation and electronic structure in InAs self-assembled quantum dots. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:11346-11353. [PMID: 9984923 DOI: 10.1103/physrevb.54.11346] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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