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Lee, Ka Yuk. "Optical properties of GaSb/AlSb/InAs-based quasi-type I quantum structures /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20LEE.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 44-48). Also available in electronic version. Access restricted to campus users.
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Wang, Jun. "GSMBE growth on V-groove patterned substrates for InP-based quantum wires /." *McMaster only, 1997.
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LaPierre, Ray R. "Atomic hydrogen-assisted epitaxy for the reduction of composition modulation in InGaAsP /." *McMaster only, 1997.
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Liang, Yu-Han. "Deep Ultraviolet Light Emitters Based on (Al,Ga)N/GaN Semiconductor Heterostructures." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1008.
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Deep ultraviolet (UV) light sources are useful in a number of applications that include sterilization, medical diagnostics, as well as chemical and biological identification. However, state-of-the-art deep UV light-emitting diodes and lasers made from semiconductors still suffer from low external quantum efficiency and low output powers. These limitations make them costly and ineffective in a wide range of applications. Deep UV sources such as lasers that currently exist are prohibitively bulky, complicated, and expensive. This is typically because they are constituted of an assemblage of two to three other lasers in tandem to facilitate sequential harmonic generation that ultimately results in the desired deep UV wavelength. For semiconductor-based deep UV sources, the most challenging difficulty has been finding ways to optimally dope the (Al,Ga)N/GaN heterostructures essential for UV-C light sources. It has proven to be very difficult to achieve high free carrier concentrations and low resistivities in high-aluminum-containing III-nitrides. As a result, p-type doped aluminum-free III-nitrides are employed as the p-type contact layers in UV light-emitting diode structures. However, because of impedance-mismatch issues, light extraction from the device and consequently the overall external quantum efficiency is drastically reduced. This problem is compounded with high losses and low gain when one tries to make UV nitride lasers. In this thesis, we provide a robust and reproducible approach to resolving most of these challenges. By using a liquid-metal-enabled growth mode in a plasma-assisted molecular beam epitaxy process, we show that highly-doped aluminum containing III-nitride films can be achieved. This growth mode is driven by kinetics. Using this approach, we have been able to achieve extremely high p-type and n-type doping in (Al,Ga)N films with high aluminum content. By incorporating a very high density of Mg atoms in (Al,Ga)N films, we have been able to show, by temperature-dependent photoluminescence, that the activation energy of the acceptors is substantially lower, thus allowing a higher hole concentration than usual to be available for conduction. It is believed that the lower activation energy is a result of an impurity band tail induced by the high Mg concentration. The successful p-type doping of high aluminum-content (Al,Ga)N has allowed us to demonstrate operation of deep ultraviolet LEDs emitting at 274 nm. This achievement paves the way for making lasers that emit in the UV-C region of the spectrum. In this thesis, we performed preliminary work on using our structures to make UV-C lasers based on photonic crystal nanocavity structures. The nanocavity laser structures show that the threshold optical pumping power necessary to reach lasing is much lower than in conventional edge-emitting lasers. Furthermore, the photonic crystal nanocavity structure has a small mode volume and does not need mirrors for optical feedback. These advantages significantly reduce material loss and eliminate mirror loss. This structure therefore potentially opens the door to achieving efficient and compact lasers in the UV-C region of the spectrum.
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Gupta, Archana. "Characterization and modeling of strained layers grown on V-grooved substrates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30143.pdf.
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Choi, Joon Koo. "Laser Spectroscopy of Eu Centres in MBE Grown CaF₂:Eu-CdF₂ Superlattices and CaF₂:Eu Thin Films." Thesis, University of Canterbury. Physics and Astronomy, 2009. http://hdl.handle.net/10092/3025.
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Molecular beam epitaxy (MBE) grown CaF₂-CdF₂ superlattices (SLs) and CaF₂ thin films doped with Eu ions were investigated by laser spectroscopic techniques. Eu ions were selectively doped into CaF₂ layers and were used as an optical probe to the SLs and thin films. Physical properties of the SLs and thin films were inferred from optical transitions of divalent and trivalent Eu centres. The 4ƒ⁶5d → 4ƒ⁷ transition of Eu²⁺ has shown strain dependent peak shifts of the zero phonon line. These shifts were thought to be a result of deformation in the crystal structure primarily due to the lattice mismatch with the Si substrate. Based on the amount of shifts, the strains associated with the MBE samples were calculated. Photoluminescence (PL) bleaching and its recovery of the same transition of Eu²⁺ in SLs were also explored. At low temperature the bleaching is best described as bi-exponential decay. Localisation of the liberated electrons from the 4ƒ⁶5d absorption band was considered for the bleaching effect. It was observed that at elevated temperatures the PL intensity of the 4ƒ⁶5d → 4ƒ⁷ transition was recovered. Combined excitation-emission spectroscopy (CEES) was employed to investigate trivalent Eu centres in SLs. The strong ⁷F₀ → ⁵D₁ excitation and the ⁵D₀ → ⁷F₁ emission of Eu³⁺ were studied. A novel centre, which is assigned as I, of Eu³⁺ in SL was observed and investigated in comparison with the cubic centre (O centre) of Eu³⁺. Relative to the O centre the I centre has shown a strong thickness dependent PL which can be demonstrated with a mono layer (1 ML = 3.15 Å) resolution. Possible transformation of the I centre to the O centre was also observed by additional thermal and UV excitations. The I and the O centres are proposed as the same centre except for having an electron in the vicinity of the I centre.
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Lin, Wenzhi. "Growth and Scanning Tunneling Microscopy Studies of Magnetic Films on Semiconductors and Development of Molecular Beam Epitaxy/Pulsed Laser Deposition and Cryogenic Spin-Polarized Scanning Tunneling Microscopy System." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1304610814.
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Mußler, Gregor. "Growth and characterization of Ga(As,N) and (In,Ga)(As,N)." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2005. http://dx.doi.org/10.18452/15219.
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Das Thema dieser Dissertation ist das MBE-Wachstum und die Charakterisierung von Ga(As,N) und (In,Ga)(As,N). Die Arbeit beginnt mit der Optimierung des Wachstums von Ga(As,N). Aufgrund der hohen Mischbarkeitslücke von GaN in GaAs verursacht der Einbau von Stickstoff in GaAs eine strukturelle Degradation, die von der Substrattemperatur, der Stickstoffkonzentration und der Quantentopfdicke abhängt. Ein weiteres Problem bezüglich des Wachstums von Ga(As,N) sind Punktdefekte, die einen schädlichen Einfluß auf optische Eigenschaften haben. Eine thermische Behandlung verringert die Konzentration dieser Punktdefekte. Dies geht mit einer Steigerung der Photolumineszenz-Intensität einher. Punktdefekte sind zum Beispiel Stickstoff-Dimere, die sich in Gallium- oder Arsen-Vakanzen einbauen. Eine thermische Behandlung bei hohen Temperaturen bewirkt jedoch eine strukturelle Degradation im Ga(As,N)-Materialsystem, die sich in einer Abnahme der Photolumineszenz-Intensität manifestiert. Es wird gezeigt, daß die Temperatur der thermischen Behandlung, die die höchste Photolumineszenz-Ausbeute erzielt, von der Stickstoffkonzentration abhängt. Bezüglich des Wachstums von (In,Ga)(As,N) verursacht die Mischbarkeitslücke von (In,Ga)N in (In,Ga)As ebenfalls eine strukturelle Degradation. Auch im quaternären Materialsystem ist eine thermische Behandlung essentiell für die Verbesserung optischer Eigenschaften. Es wird außerdem gezeigt, daß die thermische Behandlung von (In,Ga)As eine Indiumdiffusion verursacht, die durch den Einbau von Stickstoff gestoppt wird. Die Charakterisierung von (In,Ga)(As,N) kantenemittierenden Lasern zeigt Emissionen bei Wellenlängen bis zu 1366 nm. Mit dem Einbau von Stickstoff ist ein Anstieg der Schwellstromdichte und ein Abfall der Emissionsleistung verbunden.This dissertation deals with the MBE growth and characterization of Ga(As,N) and (In,Ga)(As,N). The work commences with the optimization of the Ga(As,N) growth. Owing to a large miscibility gap of GaN in GaAs, the incorporation of nitrogen into GaAs causes a structural degradation that is dependent on the substrate temperature, the nitrogen concentration, and the quantum well thickness. Another problem related to the growth of Ga(As,N) are point defects that have a detrimental influence on optical properties. A thermal treatment of Ga(As,N) reduces the concentration of these point defects. This leads to a substantial improvement of optical properties. We will show that nitrogen split interstitials that incorporate into gallium and arsenic vacancies may be attributed to these point defects. A thermal treatment of Ga(As,N) at high temperatures, on the contrary, results in a creation of extended defects which are detrimental to optical properties. We will show that the temperature of the thermal treatment that yields the highest photoluminescence intensity is nitrogen concentration-dependent. The growth of (In,Ga)(As,N) is similar with respect to Ga(As,N). Again, one has to face a high miscibility gap of (In,Ga)N in (In,Ga)As that results in a structural degradation. A thermal treatment of (In,Ga)(As,N) is also beneficial for improving optical properties. We will show that a thermal treatment of (In,Ga)As results in an indium diffusion that is suppressed by the incorporation of nitrogen. The characterization of (In,Ga)(As,N) edge emitting lasers shows emission at wavelengths up to 1366 nm. With higher nitrogen concentrations, there is a strong increase of the threshold current density and a decrease of the output power.
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Isakov, I. "Semiconductor nanowires grown by molecular beam epitaxy for electronics applications." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1463378/.
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One-dimensional nanostructures such as semiconductor nanowires are very attractive for application in next generation electronics. This work presents an experimental study of InAs-based and ZnO-based nanowires grown by molecular beam epitaxy for electronics applications. InAs, InAsP and InAsSb nanowires were grown self-catalytically on silicon. Phosphorus incorporation was studied by means of HRTEM, XRD, EDX and PL. The phosphorus incorporation rate was shown to be 10 times smaller than that of arsenic. InAs and InAsP nanowires exhibit the wurtzite structure with a high density of stacking faults and phase boundaries. Conversely, InAsSb nanowires exhibit the zincblende structure with the density of stacking faults decreasing as the antimony content increases. Antimony incorporation and reduction of the stacking fault density improves the nanowire mobility. ZnO and ZnMgO nanowires and ZnO/ZnMgO core-shell nanowire heterostructures were grown by plasma-assisted molecular beam epitaxy on various substrates with gold particles as a growth catalyst. Nanowire growth was shown to occur only at temperatures between 700 and 850 C and Zn pressures between 1 and 3 10 7 Torr. A two-step growth procedure on silicon was implemented to increase the yield of nanowire growth. Mg incorporation was shown to be 4 times smaller than that of Zn. At Mg content higher than 20 %, MgZnO rocksalt phase segregation is observed in the as-grown samples. Core-shell nanowires were fabricated by growing the shell at a lower temperature of 500 C. ZnO nanowire field effect transistors were fabricated and optimised. High- and low-temperature transport measurements allowed determination of the bulk nanowire and contact properties. Nanowires grown on sapphire and silicon were compared. Nanowires grown on sapphire exhibit an extra donor that determines their low temperature conductivity and give a wider photoluminescence band-edge emission peak. A novel technique to measure the spectrum of deep traps in nanowire field effect transistors was implemented to study ZnO nanowires.
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Bae, Hopil. "Growth of 1.5-1.55 [micron] GaInNAsSb lasers by molecular beam epitaxy /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Norton, Peter Robert. "The molecular beam epitaxy technique for PbSe-based lead chalcogenide diode lasers." Thesis, University of Bath, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370994.
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Hauksson, Isak Sverrir. "Investigation of spontaneous and stimulated emission from ZnSe epilayers and ZnCdSe-ZnSe quantum well systems grown by molecular beam epitaxy." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/749.
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Hadji, Emmanuel. "Microcavites resonantes pour l'infrarouge a base de cdhgte." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10086.
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Ce travail porte sur l'elaboration et la caracterisation de microresonateurs optiques (microcavites resonantes) pour l'infrarouge, ainsi que sur la realisation de nouveaux composants bases sur le principe de microcavite resonante: detecteurs a microcavites, diodes electroluminescentes a cavite resonante, laser a cavite verticale a emission de surface. Les microstructures sont elaborees a base d'alliages de cadmium, mercure et tellure cd#xhg#1#-#xte, qui permettent de couvrir l'infrarouge moyen (1 - 10 m) grace a la rapide variation de leur largeur de bande interdite avec la composition x. La technique d'elaboration que nous avons principalement utilisee est l'epitaxie par jets moleculaires. Nous avons ainsi realise des miroirs de bragg reflechissant plus de 99% de la lumiere et des microresonateurs de facteur de qualite superieur a 250. En complement de cette technique d'elaboration, nous avons mis au point le depot par evaporation sous vide par canon a electrons de miroirs realises a partir des dielectriques zns et yf#3. Ce type de miroir permet d'etudier la luminescence des microcavites sous excitation optique. Les principaux resultats obtenus sont d'une part le renforcement de l'absorption d'une fine couche de cdhgte, placee au sein d'une structure modele a cavite resonante. D'autre part, nous avons demontre la possibilite de realiser des emetteurs infrarouges fonctionnant a temperature ambiante sous la forme de diodes electroluminescentes a cavite resonante. Ces emetteurs presentent des proprietes optiques nouvelles qui sont induites par la microcavite resonante (largeur de raie fortement diminuee, directivite accrue, longueur d'onde d'emission peu sensible a la temperature). Enfin nous avons realise pour la premiere fois un laser photopompe a cavite verticale a emission de surface, fonctionnant a 10 k avec un seuil laser de 45 kw/cm#2
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Wang, Yongqian. "Nanometer characterization of quantum compound semiconductor heterostructures grown by molecular beam epitaxy." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20192.
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Davis, Carl Steven. "Studies of group III-nitride semiconductor compounds grown by molecular beam epitaxy." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423657.
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Vijendran, Sanjay. "Fabrication of three-dimensional semiconductor devices using focused ion molecular beam epitaxy." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621997.
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Bodin-Deshayes, Claire. "Epitaxie par jets moléculaires d'hétérostructures CdTe-CdMnTe : application aux structures laser et structures piézoélectriques." Grenoble 1, 1993. http://www.theses.fr/1993GRE10139.
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Des heterostructures de semiconducteurs ii-vi en cdte-cdmnte sont elaborees par la technique d'epitaxie par jets moleculaires (ejm). Elles sont ensuite caracterisees et etudiees en vue d'applications. Les conditions de croissance des couches de cdmnte sont optimisees selon les deux directions cristallographiques <001> et <111>. Le desaccord de maille entre le puits cdte et les barrieres cdmnte limite les structures coherentes realisables. La composition de l'alliage cdmnte, ainsi que les epaisseurs des couches sont maitrisees. Des structures de bonne qualite structurale et optique ont ete obtenues, ce qui a permis d'etudier des structures laser et des structures piezoelectriques. Des laser visibles compacts pompes electroniquement ont ete realises. Le dispositif s'appelle laser a semiconducteur a micropointe (lsm). La zone active est constituee d'une heterostructure a confinement separe et a gradient d'indice lineaire (l. Grinsch) epitaxiee selon la direction <001>. La longueur d'onde d'emission laser atteinte avec cdmnte est dans le rouge a temperature ambiante. La croissance de puits quantiques selon l'axe polaire <111> est tres interessante: l'existence d'un grand champ piezoelectrique (de l'ordre de 100000 v/cm) a ete mis en evidence experimentalement. Ce champ modifie la structure electronique et les proprietes optiques de l'heterostructure. Lors de l'ecrantage du champ par des porteurs photocrees, la raie se decale vers le bleu, ce qui est prometteur pour les applications en optique non lineaire ou en electro-optique. Pour expliquer les resultats experimentaux, l'hypothese d'une non-linearite du coefficient piezoelectrique a ete emis
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彭澤厚 and Chak-hau Pang. "A study of Mg doping in GaN during molecular beam epitaxy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31226619.
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Pang, Chak-hau. "A study of Mg doping in GaN during molecular beam epitaxy /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25059075.
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Dagnall, Georgiana. "Solid source molecular beam epitaxial growth of 155-um InAsP/InGaAsP edge-emitting lasers." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15614.
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Chubb, Daniel Edward. "LEDs and lasers for wavelengths >2um grown on InP using strain relaxed buffers." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310457.
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Lee, Kyeongkyun. "Modeling and optimization of molecular beam epitaxy for III-V compound semiconductor growth." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/14836.
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Chen, Howard ZeHua Yariv Amnon Yariv Amnon. "GaAs/AlxGa1-xAS quatum well lasers grown on GaAs and Si by molecular beam epitaxy /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-02212007-153159.
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Pritchett, David Chu. "Novel III-Nitride growth by ultraviolet radiation assisted metal organic molecular beam epitaxy." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28140.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Doolittle, W. Alan; Committee Member: Carter, W. Brent; Committee Member: Ferguson, Ian T.; Committee Member: Frazier, A. Bruno; Committee Member: Rincon-Mora, Gabriel A.
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Ptak, Aaron J. "Growth kinetics and doping of gallium nitride grown by RF-plasma assisted molecular beam epitaxy." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1895.
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Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xvii, 161 p. : ill. Includes abstract. Includes bibliographical references (p. 154-161).
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Zandbergen, Sander, and Sander Zandbergen. "Light-Matter Interactions in Various Semiconductor Systems." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624528.
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Semiconductors provide an interesting platform for studying light-matter interactions due to their unique electrically conductive behavior which can be deliberately altered in useful ways with the controlled introduction of confinement and doping, which changes the electronic band structure. This area of research has led to many important fundamental scientific discoveries that have in turn spawned a plethora of applications in areas such as photonics, microscopy, single-photon sources, and metamaterials. Silicon is the prevalent semiconductor platform for microelectronics because of its cost and electrical properties, while III-V materials are optimal for optoelectronics because of the ability to engineer a direct bandgap and create versatile heterojunctions by growing binary, ternary, or quaternary compounds.
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Satapathy, Dillip Kumar. "Molecular-beam epitaxy growth and structural characterization of semiconductor-ferromagnet heterostructures by grazing incidence x-ray diffraction." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=982680724.
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Satapathy, Dillip Kumar. "Molecular-beam epitaxy growth and structural characterization of semiconductor-ferromagnet heterostructures by grazing incidence x-ray diffraction." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15563.
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Diese Arbeit behandelt das Wachstum des ferromagnetischen Metalls MnAs auf halbleitendem GaAs. Die MnAs-Filme werden auf GaAs mittels der Molekularstrahlepitaxie (MBE) abgeschieden. Nukleation, Entwicklung von Gitterverzerrungen, Morphologie und Grenzflächenstruktur werden in-situ während des MBE Wachstums mit Hilfe von Beugung unter streifendem Einfall (GID) und der Beugung hochenergetischer Elektronen (RHEED) untersucht. Mit azimuthalen RHEED Messungen wurden vier Abschnitte des Nukleationsprozesses von MnAs auf GaAs(001) bestimmt. GID Messungen zeigen, dass das weitere Wachstum des MnAs Films bei einer nominellen Bedeckung von 2.5 ML über die Bildung relaxierter Inseln erfolgt, welche an Größe zunehmen und schließlich einen durchgängigen Film bilden. In einem Frühstadium bildet sich ein geordnetes Versetzungsnetzwerk an der Grenzfläche, welches die Verzerrungen aufgrund der Fehlanpassung bereits vor der vollständigen Ausbildung des durchgängigen Films abbauen. Der faszinierend komplexe Nukleationsprozess von MnAs auf GaAs(0 0 1) beinhaltet sowohl Elemente von Volmer-Weber, als auch von Stranski-Krastanov Wachstum. Die nicht einheitliche Gitterfehlanpassung beträgt 0.66% entlang der [1 -1 0] Richtung und 0.54% entlang der [1 1 0] Richtung, wie sich aus den Röntgenbeugungsmessungen ergibt. Entlang der [1 1 0] Richtung wird eine hohe Korrelation der Defekte beobachtet. Ein hochgradig periodisches Versetzungsnetzwerk mit einer Periode von 4.95 +- 0.05 nm entlang der [1 1 0] Richtung wird an der Grenzfläche gebildet und relaxiert 7.5% der Fehlanpassung. Die inhomogenen Verzerrungen aufgrund dieser periodischen Versetzungen an der Grenzfläche sind auf eine Schicht von 1.6nm Dicke beschränkt. Die Fehlanpassung entlang der [1 -1 0] Richtung wird durch die Bildung eines Koinzidenzgitters abgebaut.The present work is devoted to the growth of the ferromagnetic metal MnAs on the semiconductor GaAs by molecular-beam epitaxy (MBE). The MnAs thin films are deposited on GaAs by molecular-beam epitaxy (MBE). Grazing incidence diffraction (GID) and reflection high-energy electron diffraction (RHEED) are used in situ to investigate the nucleation, evolution of strain, morphology and interfacial structure during the MBE growth. Four stages of the nucleation process during growth of MnAs on GaAs(001) are revealed by RHEED azimuthal scans. GID shows that further growth of MnAs films proceed via the formation of relaxed islands at a nominal thickness of 2.5 ML which increase in size and finally coalesce to form a continuous film. Early on, an ordered array of misfit dislocations forms at the interface releasing the misfit strain even before complete coalescence occurs. The fascinatingly complex nucleation process of MnAs on GaAs(0 0 1) contains elements of both Volmer-Weber and Stranski-Krastanov growth. A nonuniform strain amounting to 0.66%, along the [1 -1 0] direction and 0.54%, along the [1 1 0] direction is demonstrated from x-ray line profile analysis. A high correlation between the defects is found along the GaAs[1 1 0] direction. An extremely periodic array of misfit dislocations with a period of 4.95 +- 0.05 nm is formed at the interface along the [1 1 0] direction which releases the 7.5% of misfit. The inhomogeneous strain due to the periodic dislocations is confined at the interface within a layer of 1.6 nm thickness. The misfit along the [1 -1 0] direction is released by the formation of a coincidence site lattice.
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Moldovan, Monica. "Photoluminescence investigation of compensation in nitrogen doped ZnSe." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=740.
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Thesis (Ph. D.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xiv, 154 p. : ill. Includes abstract. Includes bibliographical references (p. 148-154).
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Bernard, Alice. "Towards an electrically-injected optical parametric oscillator." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC104/document.
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Le travail présenté dans cette thèse porte sur la conception, la fabrication et la caractérisation de sources prévues pour fonctionner à la fois comme diode laser et comme oscillateur paramétrique optique. Ces lasers sont conçus pour émettre sur un mode d’ordre supérieur afin de permettre une conversion de fréquence paramétrique avec les modes fondamentaux du guide à la fréquence moitié. La diode laser et l’OPO partagent la même cavité optique ; pour assurer l’accord de phase et corriger les écarts à la structure nominale induits lors de l’élaboration par épitaxie, la largeur de ruban est utilisée comme paramètre de contrôle des indices efficaces. Les diodes proposées sont donc étroites (3-5 µm) et gravées profondément. En conséquence, il est potentiellement intéressant d’utiliser des boîtes quantiques pour limiter les recombinaisons non radiatives sur les flancs. Dans le cadre de ce travail, nous avons conçu des diodes basées sur ce principe pour les deux systèmes GaAs/AlGaAs et InGaAsP/InP, qui permettent respectivement d’obtenir potentiellement une émission OPO au voisinage de 2 µm ou de 3 µm. Dans le cas de l’InGaAsP/InP, nous avons étudié au préalable l’indice de réfraction des alliages InGaAsP dans une plage de longueur d’onde jusque-là non couverte par la littérature. Ces données ont été acquises via des mesures d’indice efficace (m-lines) de couches guidantes d’InGaAsP épitaxiées en accord de maille sur un substrat d’InP. Pour des structures laser-OPO optimisées, les simulations montrent que le seuil OPO devrait être obtenu pour une puissance de pompe intracavité de quelques centaines de mW, qu’il est réaliste d’atteindre pour des diodes laser à l’état de l’art. Nous avons étudié les propriétés électro-optiques de diodes lasers à puits quantiques GaAs/AlGaAs réalisées sur la base de nos dessins; l’observation de l’effet laser sur le mode TE2 valide le dessin vertical original de nos diodes lasers. En vue de la fabrication de laser-OPO à ruban étroit, nous avons développé des procédés de fabrication nouveaux sur la Plateforme Technologique Amont (CEA – Grenoble), notamment la gravure profonde (>10 µm) par ICP-RIE. Enfin, nous avons proposé un concept alternatif de diode-OPO, comprenant des cavités laser et OPO distinctes couplées par un taper adiabatiqueThe work presented in this thesis deals with the design, fabrication and characterization of sources intended to function as both laser diodes and optical parametric oscillators. These lasers are designed to emit on a higher order mode to allow parametric frequency conversion with fundamental modes of the guide at half frequency. The laser diode and OPO share the same optical cavity; to ensure phase matching and correct nominal structure deviations induced during epitaxial processing, the ridge width is used as a control parameter of the effective indices. The proposed diodes are therefore narrow (3-5 μm) and etched deeply. Consequently, it is potentially interesting to use quantum dots to limit non-radiative recombination on the sidewalls. In the context of this work, we have designed diodes based on this principle for the two GaAs/AlGaAs and InGaAsP/InP systems, which respectively allow to potentially obtain an OPO emission in the vicinity of 2 μm or 3 μm. In the case of InGaAsP/InP, we previously studied the refractive index of InGaAsP alloys in a wavelength range not covered by literature to this day. This data was acquired via effective m-line index measurements of InGaAsP guiding layers epitaxially grown on and lattice-matched to an InP substrate. For optimized laser-OPO structures, simulations show that the OPO threshold should be obtained for an intracavity pump power of a few hundred mW, which is realistic to achieve for state-of-the-art laser diodes. We have studied the electro-optical properties of GaAs/AlGaAs quantum well laser diodes made on the basis of our designs; the observation of the laser effect on the TE2 mode validates the original vertical design of our laser diodes. For the manufacture of narrow-ridge lasers-OPOs, we have developed new manufacturing processes on the Plateforme Technologique Amont (Upstream Technology Platform, CEA - Grenoble), including deep etching (> 10 μm) by ICP-RIE. Finally, we have proposed an alternative diode-OPO concept, comprising distinct laser and OPO cavities coupled by an adiabatic taper
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Burnham, Shawn David. "Improved understanding and control of Mg-doped GaN by plasma assisted molecular beam epitaxy." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06122007-133821/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Doolittle, W. Alan, Committee Chair ; Ferguson, Ian T., Committee Member ; Cressler, John D., Committee Member ; Dorsey, John F., Committee Member ; Carter, W. Brent, Committee Member.
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Al-Brithen, Hamad A. H. "Scanning Tunneling Microscopy Investigation of Rock-salt and Zinc-blende Nitrides Grown by Molecular Beam Epitaxy." Ohio University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1107274641.
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Moldawer, Adam Lyle. "Growth of polar and non-polar nitride semiconductor quasi-substrates by hydride vapor phase epitaxy for the development of optoelectronic devices by molecular beam epitaxy." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11151.
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Thesis (Ph.D.)--Boston UniversityThe family of nitride semiconductors has had a profound influence on the development of optoelectronics for a large variety of applications. However, as of yet there are no native substrates commercially available that are grown by liquid phase methods as with Si and GaAs. As a result, the majority of electronic and optoelectronic devices are grown heteroepitaxially on sapphire and SiC. This PhD research addresses both the development of polar and nonpolar GaN and AIN templates by Hydride Vapor Phase Epitaxy (HVPE) on sapphire and SiC substrates, as well as the growth and characterization of optoelectronic devices on these templates by molecular beam epitaxy (MBE). Polar and non-polar GaN templates have been grown in a vertical HVPE reactor on the C- and R-planes of sapphire respectively. The growth conditions have been optimized to allow the formation for thick (50µm) GaN templates without cracks. These templates were characterized structurally by studying their surface morphologies by SEM and AFM, and their structure through XRD and TEM. The polar C-plane GaN templates were found to be atomically smooth. However, the surface morphology of the non-polar GaN films grown on the R-plane of sapphire were found to have a facetted surface morphology, with the facets intersecting at 120° angles. This surface morphology reflects an equilibrium growth, since the A-plane of GaN grows faster than the M-planes of GaN due to the lower atomic density of the plane. For the development of deep-UV optoelectronics, it is required to grow AIGaN quantum wells on AIN templates. However, since AIN is a high melting point material, such templates have to be grown at higher temperatures, close to half the melting point of the material (1500 °C). As these temperatures cannot be easily obtained by traditional furnace heating, an HVPE reactor has been designed to heat the substrate inductively to these temperatures. This apparatus has been used to grow high-quality, transparent AIN films with a screw dislocation density of 10^6 cm^-2 on sapphire repeatedly. On such templates, both lnGaN- and AIGaN-based quantum wells (QWs) and quantum dots (QDs) were formed by MBE and were characterized. lnGaN/GaN and AIGaN/AIN QWs were grown on the non-polar GaN templates and found to emit at near green and deep UV respectively with internal quantum efficiency (IQE) close to 90%. The lnGaN GaN QWs and QDs have been investigated to understand the influence of plasmonic nanoparticles on the efficiency of corresponding green LEOS.
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Cooke, Paul William. "A novel bistable laser of optoelectronic integration : demonstration of the Double Heterostructure Optoelectronic Switch as a low threshold using Molecular Beam Epitaxy." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277154.
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Srinivasan, Prasanna. "Substrate cleaning using a remote hydrogen RF-plasma." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1215.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains x, 72 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 69-72).
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Ma, King-man Simon. "Structure determination by low energy electron diffraction of GaN films on 6H-SiC(0001) substrate by molecular beam epitaxy." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36537524.
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Ma, King-man Simon, and 馬勁民. "Structure determination by low energy electron diffraction of GaN films on 6H-SiC(0001) substrate by molecular beam epitaxy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36537524.
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Yang, Rong. "ATOMIC-SCALE AND SPIN STRUCTURE INVESTIGATIONS OF MANGANESE NITRIDE AND RELATED MAGNETIC HYBRID STRUCTURES PREPARED BY MOLECULAR BEAM EPITAXY." Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1152124059.
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Gaucher, Samuel. "Growth of lattice-matched hybrid semiconductor-ferromagnetic trilayers using solid-phase epitaxy." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22599.
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Diese Arbeit befasst sich mit dem Wachstum von Dünnschichtstrukturen, die zur Herstellung eines Spin-selektiven Schottky-Barrier-Tunneltransistors (SS-SBTT) erforderlich sind. Das Bauelement basiert auf dem Transport von Ladungsträgern durch eine dünne halbleitende (SC) Schicht, die zwei ferromagnetische (FM) Kontakte trennt. Daher müssen hochqualitative und gitterangepasste vertikale FM/SC/FM-Trilayer gezüchtet werden, was aufgrund der inkompatiblen Kristallisationsenergien zwischen SC und Metallen eine experimentelle Herausforderung darstellt. Das Problem wurde mit einem Festphasenepitaxie-Ansatz gelöst, bei dem eine dünne amorphe Ge-Schicht (4-8 nm) durch Ausglühen über Fe3Si auf GaAs(001)-Substraten kristallisiert wird. Langsame Glühgeschwindigkeiten bis zu einer Temperatur von 260°C konnten ein neues gitterangepasstes Polymorph von FeGe2 erzeugen, über das ein zweites Fe3Si mittels Molekularstrahlepitaxie gezüchtet werden könnte. SQUID-Magnetometermessungen zeigen, dass die dreischichtigen Proben in antiparallele Magnetisierungszustände versetzt werden können. Vertikale Spin-Ventil-Bauelemente, die mit verschiedenen Trilayern hergestellt wurden, wurden verwendet, um zu demonstrieren, dass der Ladungstransport über die Heteroübergänge spinselektiv ist und bei Raumtemperatur einen Magnetowiderstand von höchstens 0,3% aufweist. Der Effekt nimmt bei niedrigen Temperaturen ab, was mit einem ferromagnetischen Übergang in der FeGe2-Schicht korreliert. Durch TEM- und XRD-Experimente konnte festgestellt werden, dass das neue FeGe2-Polymorph die Raumgruppe P4mm aufweist und bis zu 17% Si-Atome als Ersatz für Ge-Stellen enthält. Die Isolierung von FeGe2 war möglich, indem das Verhältnis von Fe-, Si- und Ge-Atomen so eingestellt wurde, dass die richtige Stöchiometrie bei vollständiger Durchmischung erreicht wurde. Anhand von FeGe2-Dünnschichten wurde ein zunehmender spezifischer Widerstand bei niedriger Temperatur und ein semi-metallischer Charakter beobachtet.This thesis discusses the growth of thin film structures required to fabricate a Spin-Selective Schottky Barrier Tunnel transistor (SS-SBTT). The device relies on charge carriers being transported through a thin semiconducting (SC) layer separating two ferromagnetic (FM) contacts. Thus, high quality and lattice-matched FM/SC/FM vertical trilayers must be grown, which is experimentally challenging due to incompatible crystallization energies between SC and metals. The problem was solved using a solid-phase epitaxy approach, whereby a thin amorphous layer of Ge (4-8 nm) is crystallized by annealing over Fe3Si on GaAs(001) substrates. Slow annealing rates up to a temperature of 260°C could produce a lattice-matched Ge-rich compound, over which a second Fe3Si could be grown my molecular-beam epitaxy. The compound obtained during annealing is a new layered polymorph of FeGe2. SQUID magnetometry measurements indicate that the trilayer samples can be placed in states of antiparallel magnetization. Vertical spin valve devices created using various trilayers were used to demonstrate that charge transport is spin-selective across the heterojunctions, showing a magnetoresistance of at most 0.3% at room temperature. The effect decreases at low temperature, correlating with a ferromagnetic transition in the FeGe2 layer. TEM and XRD experiments could determine that the new FeGe2 polymorph has a space group P4mm, containing up to 17% Si atoms substituting Ge sites. Isolating FeGe2 was possible by tuning the proportion Fe, Si and Ge atoms required to obtain the right stoichiometry upon full intermixing. Hall bars fabricated on FeGe2 thin films were used to observe an increasing resistivity at low temperature and semimetallic character.
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Kent, Thomas Frederick. "III-Nitride Nanostructures for Optoelectronic and Magnetic Functionalities: Growth, Characterization and Engineering." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408564155.
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Pfeuffer, Rebekka Christina [Verfasser], and Charles [Gutachter] Gould. "Growth and characterization of II-VI semiconductor nanowires grown by Au catalyst assisted molecular beam epitaxy / Rebekka Christina Pfeuffer ; Gutachter: Charles Gould." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1121508308/34.
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Fay, Michael W. "Advanced electron microscopy of wide band-gap semiconductor materials." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340213.
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Lee, William (Chun-To). "Harvesting Philosopher's Wool: A Study in the Growth, Structure and Optoelectrical Behaviour of Epitaxial ZnO." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2507.
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This thesis is about the growth of ZnO thin films for optoelectronic applications. ZnO thin films were grown using plasma assisted molecular beam epitaxy and were studied using various conventional and novel characterisation techniques. The significance of different growth variables on growth efficiency was investigated. The growth rate of ZnO films was found to be linearly dependent on the Zn flux under O-rich growth conditions. Under Zn-rich conditions, the growth rate was dependent on both atomic and molecular oxygen flux. By characterising the oxygen plasma generated using different RF power and aperture plate designs and correlating the results with the growth rates observed, it was found that atomic oxygen was the dominant growth species under all conditions. Molecular oxygen also participated in the growth process, with its importance dependent on the aperture plate design. In addition, an increase in growth temperature was found to monotonically decrease the growth rate. A growth rate of 1.4 Å/s was achieved at a growth temperature of 650 ℃ by using an oxygen flow rate of 1.6 standard cubic centimetres utilising a plasma source with a 276 hole plate operating at 400 W, and a Zn flux 1.4✕10¹⁵ atoms/cm²⋅s. Characterisation of the MBE grown thin films revealed that the qualities of ZnO thin films were dependent on the growth conditions. Experimental evidence suggested that a maximum adatom diffusion rate can be achieved under Zn-rich conditions, giving samples with the best structural quality. O-rich conditions in general led to statistical roughening which resulted in rough and irregular film surfaces. Experimental results also suggested that by increasing the atomic oxygen content and decreasing the ion content of the plasma, the excitonic emission of the ZnO thin films can possibly be improved. It was also found that the conductivity of the films can possibly be reduced by increasing the plasma ion content. By investigating the evolution of the buffer layer surface during the early stages of growth, dislocation nucleation and surface roughening were found to be important strain relief mechanisms in MBE grown ZnO thin films that affected the crystal quality. The usage of LT-buffer layers was found to improve substrate wetting, and was shown to significantly reduce dislocation propagation. Further strain reduction was achieved via the application of a 1 nm MgO buffer layer, and a significant reduction of carrier concentration and improvement in optical quality was subsequently observed. A carrier concentration of <1✕10¹⁶ cm⁻³ and a near band emission full width half maximum of 2 meV was observed for the best sample. The study of electrical characteristics using the variable magnetic field Hall effect confirmed the existence of a degenerate carrier and a bulk carrier in most MBE grown ZnO thin films. The bulk carrier mobility was measured to be ~120 - 150 cm²/Vs for most as-grown samples, comparable to the best reported value. A typical bulk carrier concentration of ~1✕10¹⁶ - 1✕10¹⁸ cm⁻³ was observed for as-grown samples. Annealing was found to increase the mobility of the bulk carrier to ~120 - 225 cm²/Vs and decrease the bulk carrier concentration by two orders of magnitude. Using time resolved photoluminescence, it was found that the radiative recombination in MBE grown ZnO thin films was dominated by excitonic processes, and followed a T³⁄² trend with temperature. A maximum radiative lifetime of 10 ns was observed for as-grown samples. The non-radiative lifetime in ZnO thin films was dominated by the Shockley-Read-Hall recombination processes. The modelling of the temperature dependence of the non-radiative lifetime suggested that an electron trap at ~0.065 eV and a hole trap at ~0.1 eV may be present in these samples. The application of time resolved photoluminescence also allowed the direct observation of carrier freeze-out in these ZnO films at low temperature.
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Elfving, Anders. "Near-infrared photodetectors based on Si/SiGe nanostructures." Doctoral thesis, Linköping : Surface and Semiconductor Physics, Linköping University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5909.
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Chen, Jihong. "Surface reactions of digermane, diethylgermane, triethylgermane, and deuterated ethylbromide on the GE(100) surface /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9737909.
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Belahsene, Sofiane. "Lasers moyen infrarouge innovants pour analyse des hydrocarbures." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20166/document.
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L'objectif de cette thèse, réalisée dans le cadre du contrat européen Senshy, était la réalisation de diodes laser émettant dans le moyen infrarouge (de 3,0 à 3,4 µm). Ces diodes sont destinées à intégrer des détecteurs et des systèmes d'analyse de gaz basés sur le principe de la spectroscopie d'absorption (TDLAS) pour la détection des alcanes (méthane, éthane, propane) et des alcènes (acétylène). Les structures à puits quantiques de type I ont été réalisées par épitaxie par jets moléculaires sur GaSb.Bien qu'ayant d'excellentes performances dans la gamme 2,0-3,0 µm, les lasers GaInAsSb/AlGaAsSb montrent rapidement leurs limites en franchissant la frontière des 3 µm (la longueur d'onde la plus haute atteinte avec un tel composant est de 3,04 µm en continu à 20°C). Cette situation était d'autant plus regrettable que plusieurs gaz ont leurs raies d'absorption au-delà de 3 µm : le méthane par exemple a un pic d'absorption à 3,26 µm 40 fois plus fort que celui à 2,31 µm. En remplaçant le quaternaire AlGaAsSb par le quinaire AlGaInAsSb, nous avons montré que l'on pouvait améliorer l'efficacité quantique interne et avons obtenu des densités de courant de seuil à 2,6, 3,0 et 3,3 µm qui pouvaient être comparées favorablement aux précédents records à ces longueurs d'onde (respectivement, 142 A/cm², 255 A/cm² et 827 A/cm²).Les diodes laser DFB fabriquées à partir des structures epitaxiées ont permis d'atteindre l'émission laser à température ambiante en continu à 3,06 µm avec un caratère mono-fréquence (SMSR supérieur à 30 dB) et un courant de seuil de 54 mA. À 3,3 µm, les diodes DFB fonctionnent en continu jusqu'à 18°C avec un SMSR > 30dB et un courant de seuil de 140 mA. Finalement, ces diodes ont été intégrées dans un système d'analyse de gaz et ont permis d'atteindre une limite de concentration du méthane de 100 ppbv soit 17 fois moins que la concentration du méthane dans l'air ambiantThe objective of this thesis, conducted as part of the European contract Senshy, was the realization of laser diodes emitting in the mid-infrared range (from 3.0 to 3.4 µm). These devices are to be integrated into detectors and gas analysis systems based on the principle of absorption spectroscopy (TDLAS). for the detection of alkanes (methane, ethane, propane) and of alkenes (acetylene). The quantum well type-I structures were made by molecular epitaxy on GaSb. Despite having excellent performance in the 2 to 3 µm range, GaInAsSb/AlGaAsSb quantum well lasers rapidly show their limits when crossing the 3 µm barrier (the highest wavelength reached with such a device was 3.04 µm under cw operation at 20°C). This situation was all the more regrettable because several gases have their strongest absorption lines in the 3 to 4 µm range: methane, for example, has a peak of absorption at 3.26 µm overhanging a weaker peak at 2.31 µm by a factor 40. By replacing the quaternary AlGaAsSb by the quinary AlGaInAsSb, we have shown that the internal efficiency could be improved and we have obtained threshold current densities at 2.6 , 3.0 and 3,3 µm that could be favourably compared to the previous records at these wavelengths (respectively, 142 A/cm², 255 A/cm² and 827 A/cm²).DFB laser diodes made from the epitaxial structures were operated at room temperature in the continuous wave regime at 3.06 µm with a single-frequency emission (SMSR greater than 30dB) and a threshold current of 54 mA. At 3.3 µm, DFB devices were operated in cw up to 18 ° C with a SMSR > 30 dB and a current threshold of 140 mA. Eventually, these devices were integrated into a gas analysis system and allowed to reach a concentration limit of 100 ppbv of methane, i.e. 17 times less than the concentration of methane in the air
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Le, Ru Eric C. "Propriétés optiques des boîtes quantiques d'InAs pour les applications à grande longueur d'onde." Palaiseau, Ecole polytechnique, 2002. http://www.theses.fr/2002EPXX0035.
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Rueda-Fonseca, Pamela. "Magnetic quantum dots in II-VI semiconductor nanowires." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GRENY015/document.
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Dans ce travail de thèse a été développé et étudié un nouveau type d'objet semiconducteur magnétique : des boîtes quantiques de CdMnTe insérées dans des nanofils de ZnTe/ZnMgTe constituant une structure de type cœur-coquille. L'objectif était d'étudier la croissance par épitaxie par jets moléculaires et les propriétés fondamentales de ces hétéro-structures complexes. Dans ce but deux aspects principaux ont été abordés : i) la qualité et le contrôle des propriétés structurales, électroniques et magnétiques de ces objets, grâce à une maîtrise de leur croissance et ii) l'obtention d'informations quantitatives locales sur la composition chimique de ces nanostructures inhomogènes. Pour atteindre ces objectifs, nous avons divisé notre étude en quatre étapes. La première étape de ce travail a été concentrée sur l'étude quantitative de la formation des particules d'or servant de catalyseurs à la croissance des nanofils. La seconde étape a porté sur l'analyse des mécanismes de croissance et des paramètres gouvernant la croissance des fils de ZnTe. En particulier deux types de fils ont été observés : des fils cylindriques de structure wurtzite et des fils coniques de structures zinc-blende. Un modèle de croissance guidée par la diffusion a été utilisé pour rendre compte de certains des résultats quantitatifs présentés dans cette partie. La troisième étape a concerné l'insertion de boîtes quantiques de CdMnTe dans des nanofils de structure cœur-coquille ZnTe/ZnMgTe. Une étude préalable des paramètres pertinents influençant les propriétés magnéto-optiques de ces objets, tels que le confinement de la boîte quantique, l'incorporation du Mn et l'anisotropie de contrainte créée par la structure, a été menée. La quatrième et dernière étape de ce travail a porté sur l'interprétation quantitative de mesures d'analyse dispersive en énergie effectuées sur des nanofils de structure cœur-multicoquille. Un modèle géométrique a été proposé, permettant de retrouver la forme, les dimensions et la composition chimique des boîtes quantiques et des coquilles. Cette étude a été couplée à des mesures de caractérisation telles que la cathodo-luminescence, la micro-photo-luminescence et la spectroscopie magnéto-optique effectuées sur le même nanofilIn this PhD work a novel type of magnetic semiconductor object has been developed: Cd(Mn)Te quantum dots embedded in ZnTe/ZnMgTe core-shell nanowires. The goal was to investigate the growth, by molecular beam epitaxy, and the fundamental properties of these complex heterostructures. For that purpose, two main issues were addressed: i) gaining control of the structural, electronic and magnetic properties of these quantum objects by mastering their growth; and ii) obtaining quantitative local knowledge on the chemical composition of those non-homogeneous nanostructures. To tackle these topics, our research was divided into four stages. The first stage was devoted to perform a quantitative study of the formation process of the Au particles that catalyze the growth of nanowires. The second stage involved the analysis of the mechanisms and parameters governing the growth of ZnTe nanowires. In particular, two different types of nanowires were found: cone-shaped nanowires with the zinc-blende crystal structure and cylinder-shaped nanowires with the hexagonal wurtzite structure. A diffusion-driven growth model is employed to fit some of the quantitative results presented in this part. The third stage focused on the insertion of pure CdTe quantum dots containing Mn ions in the core-shell nanowires. An initial study of the relevant parameters influencing the magneto-optical properties of these objects, such as the quantum dot confinement, the Mn incorporation, and the strain anisotropy, was performed. The four and last stage of this work concerned the quantitative interpretation of Energy-Dispersive X-ray spectroscopy measurements performed on single core-multishell nanowires. A geometrical model was proposed to retrieve the shape, the size and the local composition of the quantum dot insertions and of the multiple layers of the heterostructures. This study was coupled to other complementary characterization measurements on the same nanowire, such as cathodo-luminescence, micro-photo-luminescence and magneto-optical spectroscopy
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Chmielewski, Daniel Joseph. "III-V Metamorphic Materials and Devices for Multijunction Solar Cells Grown via MBE and MOCVD." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534707692114982.
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Das, Aparna. "Boîtes quantiques de semi-conducteurs nitrures pour des applications aux capteurs opto-chimiques." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00870365.
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Ce travail de thèse a porté sur la synthèse de boîtes quantiques (BQs) de semi-conducteurs nitrures orientés (11-22) ou (0001) par épitaxie par jets moléculaires à plasma d'azote, pour des applications aux capteurs chimiques pour la détection du niveau de pH, d'hydrogène ou des hydrocarbures dans des environnements gazeux ou liquides. Dans la première partie de ce manuscrit, je décri la synthèse des couches bidimensionnelles semi-polaires (11-22) : des couches binaires (AlN, GaN, and InN) et des ternaires (AlGaN et InGaN), qui sont requises pour le contact de référence dans les transducteurs et aussi pour établir une connaissance de base pour comprendre la transition dès la croissance bidimensionnelle à la croissance tridimensionnel des BQs. Un résultat particulièrement relevant est l'étude de la cinétique de croissance et l'incorporation de l'indium dans les couches d'InGaN(11-22). De même que pour InGaN polaire (0001), les conditions optimales de croissance pour l'orientation cristallographique semi-polaire correspondent à la stabilisation de 2 ML d'In sur la surface, en excellent accord avec des calculs théoriques. Les limites de la fenêtre de croissance en termes de température du substrat et de flux d'In sont les mêmes pour les matériaux semi-polaire et polaires. Cependant, j'ai constaté une inhibition de l'incorporation de l'In dans les couches semi-polaires, même pour une température en dessous du seuil de la ségrégation pour l'InGaN polaire. Dans une deuxième étape, j'ai fabriqué des super-réseaux de BQs de GaN/AlN et InGaN/GaN, à la fois dans l'orientation polaire et semi-polaire. Les mesures de photoluminescence et de photoluminescence en temps résolu confirment la réduction du champ électrique interne dans les boîtes semi-polaires. D'autre part, les BQs semi-polaires à base d'InGaN doit relever le défi de l'incorporation d'In dans cette orientation cristallographique. Pour surmonter ce problème, l'influence de la température de croissance sur les propriétés des boîtes quantiques InGaN polaires et semi-polaires a été étudiée, en considérant la croissance à haute température (TS = 650-510 °C, où la désorption d'In est active) et à basse température (TS = 460-440 °C, où la désorption d'In est négligeable). J'ai démontré que les conditions de croissance à faible TS ne sont pas compatibles avec le plan polaire, tandis qu'ils fournissent un environnement favorable au plan semi-polaire pour améliorer l'efficacité quantique interne de nanostructures InGaN. Enfin, j'ai synthétisé un certain nombre de transducteurs à BQs de GaN/AlN et InGaN/GaN selon les axes de croissance polaire et semi-polaire. Dans chaque cas, les conditions de croissance pour atteindre la fourchette spectrale ciblée (420-450 nm d'émission à avec une couche contact transparente pour des longueurs d'onde plus courtes que 325 nm) ont été identifiés. L'influence d'un champ électrique externe sur la luminescence des transducteurs ont confirmé que la meilleure performance (plus grande variation de la luminescence en fonction de la polarisation) a été fournie par des structures à base de BQs d'InGaN/GaN. Avec ces données, les spécifications des transducteurs opto-chimiques ont été fixées : 5 perides de BQs d'InGaN/GaN sur une couche contact d'Al0.35Ga0.65N:Si). Puis, j'ai synthétisé un certain nombre de ces transducteurs afin d'obtenir un aperçu sur la reproductibilité, limites et les étapes critiques du processus de fabrication. En utilisant ces échantillons, nous avons réalisé un système capteur intégré qui a été utile pour le suivi de la valeur du pH de l'eau.