Dissertations / Theses on the topic 'InGaAs quantum dots'
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Larsson, Arvid. "Optical spectroscopy of InGaAs quantum dots." Doctoral thesis, Linköpings universitet, Halvledarmaterial, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-64707.
Full textArbetet som presenteras i denna avhandling rör studier av kvantprickars optiska egenskaper. En kvantprick är en halvledarkristall som endast är några tiotals nanometer stor. Den ligger oftast inbäddad inuti en större kristall av ett annat halvledarmaterial och pga. den begränsade storleken får en kvantprick mycket speciella egenskaper. Bland annat så kommer elektronerna i en kvantprick endast att kunna anta vissa diskreta energinivåer liknande situationen för elektronerna i en atom. Följaktligen kallas kvantprickar ofta för artificiella atomer. För halvledarmaterial gäller det generellt att det inte endast är fria elektroner i ledningsbandet, som kan leda ström utan även tomma elektrontillstånd i valensbandet, vilka uppträder som positivt laddade partiklar, kan leda ström. Dessa kallas kort och gott för hål. I en kvantprick har hålen såsom elektronerna helt diskreta energinivåer. Precis som är fallet i en atom, så kommer elektroniska övergångar mellan olika energinivåer i en kvantprick att resultera i att ljus emitteras. Energin (dvs. våglängden alt. färgen) för detta ljus bestäms av hur energinivåerna i kvantpricken ligger, för elektronerna och hålen, och genom att analysera ljuset kan man således studera kvantprickens egenskaper. Studierna i den här avhandlingen visar att växelverkan mellan en kvantprick och den omgivande kristallen, som den ligger inbäddad i, har stor inverkan på kvantprickens optiska egenskaper. T.ex. visas att man kan kontrollera antalet elektroner, som kommer att finnas i kvantpricken genom att modifiera hur elektronerna kan röra sig i omgivningen. Dessa rörelser modifieras här genom att variera temperaturen och genom att lägga på ett magnetiskt fält. Ett magnetiskt fält, vinkelrätt mot en elektrons rörelse, kommer att böja av dess bana och dess chans att nå fram till kvantpricken kan således minskas. Elektronen kan då istället fastna i andra potentialgropar i kvantprickens närhet. Genom att öka temperaturen, vilket ger elektronerna större energi, kan deras chans att nå fram till kvantpricken å andra sidan öka. En annan effekt, som studerats, är möjligheten att kontrollera spinnet hos elektronerna i en kvantprick. Även i dessa studier visar det sig att växelverkan med omgivningen spelar stor roll och kan användas till att kontrollera elektronens spin. Mekanismen som föreslås är att om elektronerna hinner före hålen till kvantpricken, så hinner de överföra sitt spin till atomkärnorna i kvantpricken. På detta sätt kan man få atomkärnornas spin polariserat, vilket resulterar i ett inbyggt magnetfält, i storleksordningen 1.5 Tesla, som i sin tur hjälper till att upprätthålla en hög grad av spinpolarisering även hos elektronerna. För att få elektronerna att hinna först, måste deras rörelser i omgivningen kontrolleras. I en ytterligare studie undersöktes den process där en elektronisk övergång i kvantpricken inte enbart resulterar i emission av ljus, utan även i att en annan partikel tar över en del av energin och blir exciterad. Dessa processer avspeglas i att en del av det ljus som emitteras har lägre energi. Detta ljus är också mycket svagt, ca 1000 ggr lägre intensitet, och möjligheten att kunna mäta detta är helt beroende på hur ljusstarka kvantprickarna är. De prover som använts i denna studie består av pyramidstrukturer, ca 7.5 mikrometer stora, med kvantprickar inuti. Denna geometri ger ca 1000 ggr bättre ljusutbyte jämfört med traditionella strukturer, vilket möjliggjort studien.
Park, Tyler Drue. "Characterization of InGaAs Quantum Dot Chains." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3718.
Full textFry, Paul William. "Optical spectroscopy of InGaAs GaAs self assembled quantum dots." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275221.
Full textBrereton, Peter George. "Control of single InGaAs quantum dots with frequency-swept optical pulses." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610893.
Full textBaer, Norman. "Optical and electronic properties of InGaAs and nitride quantum dots." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=983398089.
Full textKarlsson, Fredrik. "Spectroscopic studies of InGaAs/GaAs/AlGaAs quantum dots and wires /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek892s.pdf.
Full textCesari, Valentina. "Ultrafast carrier dynamics in P doped InGaAs GaAs quantum dots." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54834/.
Full textOulton, Ruth. "Optical spectroscopy of single self-assembled InGaAs/GaAs quantum dots." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401132.
Full textMigliorato, Max Antonio. "Atomistic modelling of InGaAs quantum dots with non-uniform composition." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289689.
Full textKoseki, Shinichi. "Monolithic waveguide coupled GaAs microdisk microcavity containing ingaas quantum dots /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full textSiverns, Philip Douglas. "Optical and structural properties of InGaAs self assembled quantum dots." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/7354.
Full textGreilich, Alex [Verfasser]. "Spin coherence of carriers in InGaAs/GaAs quantum wells and quantum dots / Alex Greilich." Aachen : Shaker, 2007. http://d-nb.info/1166510565/34.
Full textBoyle, Stephen James. "Picosecond Coherent Control of Single Self-Assembled InGaAs GaAs Quantum Dots." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522495.
Full textChauhan, Kripa Nidhan. "Carrier Dynamics in InGaAs/GaAs Quantum Dots Excited by Femtosecond Laser Pulses." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1467.
Full textLiew, San Lin. "Advanced transmission electron microscopy studies in Si/SiGe quantum cascade emitters and InGaAs/GaAs quantum dots." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421161.
Full textHöglund, Linda. "Growth and characterisation of InGaAs-based quantum dots-in-a-well infrared photodetectors." Doctoral thesis, Linköpings universitet, Materiefysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15774.
Full textOn the day of the defence date the status on article IV was: Accepted.
Bennett, Anthony John. "A study of InGaAs/GaAs quantum dots and GaInNas/GaAs quantum wells for optoelectronic applications at 1300nm." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/8104.
Full textAlsolamy, Samar M. "The Study of Coupling in InGaAs Quantum Rings Grown by Droplet Epitaxy." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1357840899.
Full textMukai, Kohki. "Growth and Characterization of Self-Assembled InGaAs/GaAs Quantum Dots and Their Application to Lasers." Kyoto University, 2000. http://hdl.handle.net/2433/151537.
Full textKyoto University (京都大学)
0048
新制・論文博士
博士(工学)
乙第10504号
論工博第3541号
新制||工||1192(附属図書館)
UT51-2000-P671
(主査)教授 藤田 茂夫, 教授 北野 正雄, 教授 野田 進
学位規則第4条第2項該当
Klingbeil, Matthias [Verfasser]. "Manipulation of the Emission from Natural and Stranski-Krastanow InGaAs Quantum Dots by Strain / Matthias Klingbeil." München : Verlag Dr. Hut, 2013. http://d-nb.info/1035049880/34.
Full textNedzinskas, Ramūnas. "Epitaksinių InGaAs kvantinių taškų darinių moduliuoto atspindžio ir fotoliuminescencijos spektroskopija." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121001_093259-68855.
Full textSelf-assembled InAs quantum dots (QDs), whose intersublevel transition energies lie in the mid- and far-infrared spectral range (3–25μm), have attracted particular interest as active elements of infrared photodetectors. This interest is mainly due to intriguing atomic-like quantum confinement and unique optical and electronic properties of QDs. Moreover, QD electronic structure can be adjusted by varying the dots size and shape or their environment. These features make QDs to be of importance in creation of photoelectronic devices with a desired spectral range. The dissertation is concerned specifically with molecular beam epitaxy grown InGaAs QD structures with: -- InAs QD stacks embedded in GaAs matrix and GaAs/AlAs superlattice (SL), or alternatively InAs/GaAs QD-SL structures with and without AlAs barriers between the dot layers; -- InAs QDs with and without InGaAs strain-reducing layers, embedded within GaAs/AlAs quantum wells; -- columnar InGaAs QDs, also referred to as quantum rods (QRs) or quantum posts, of different morphology. (The quantum confined structure consists of vertically oriented InGaAs QRs immersed in a two-dimensional InGaAs layer). These QD structures were studied by modulated reflectance and photo- luminescence spectroscopies to reveal their optical properties and the full- extent of electronic structure. Experimental data were interpreted by numerical (nextnano3 software) and analytical (algorithm developed) modelling.
Strauß, Stefan Maximilian [Verfasser], Stephan [Akademischer Betreuer] Reitzenstein, Stephan [Gutachter] Reitzenstein, and Mete [Gutachter] Atatüre. "Coherent spectroscopy of InGaAs quantum dots / Stefan Maximilian Strauß ; Gutachter: Stephan Reitzenstein, Mete Atatüre ; Betreuer: Stephan Reitzenstein." Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1168324157/34.
Full textVaz, Alfredo Rodrigues. "Espalhamento Raman em Pontos Quânticos de InGaAs." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-14072014-163652/.
Full textInxGa1-x As islands are interesting for use in Laser diode and light-emitting diode technology. The InxGa1-x As islands investigated in this work were grown on semi-insulating (001) GaAs substrates by the self-organization method using molecular beam epitaxy. This type of island, when isolated and of small size, is considered as a quantum dot or zero-dimensional system. The samples were characterized by use of atomic force microscopy. The dot density and size were seen to increase as the In molar fraction decreased, resulting in a large dot coverage in the case of x = 0.25. The Raman spectra main features were the peaks corresponding to the LO and TO modes of GaAs-substrate. Second order structures were also present around 520 cm-1 (160 cm-1) for optical (acoustic) vibration of GaAs. Two additional structures appear as a sharp peak at 222 cm- 1 and higher energy broad band, which is resolved only for x = 0.25, at 245 cm- 1. The peak in 222 cm-1 is probably due to the normally forbidden GaAs LA(X) phonon induced by defects. To assign the broad band a model was constructed that considers: (i) the Raman frequency of the InAs-like mode with LO character as constant with x in bulk I nGaAs; (ii) confinement effects for the large dots formed has negligible effects in the quantum dot Raman frequency; (iii) The strain scale with x, the maximun value corresponds to that obtained for InAs. This model allowed to predict a range of frequencies for the dots. The value measured, 245 cm- 1, fit into this range and is, thus, attributed to the InAs-like mode of the In0.25Ga0.75As quantum dots. Selection rules arguments reinforces this assignment. Several additional contributions in the frequency range of interest were considered. In order to analyze those contributions, a detailed study of disorder induced phonons in GaAs, and Raman scattering of As-crystaline and amorphous, was realized. The disorder was produced by laser ablation and the As sample was formed by an oxidation process of an A1As film. Comparison of the Raman spectra allowed to conclude that neither As or GaAs disorder induced phonons contribute to the quantum-dot spectrum.
Wen, Xiaoming, and n/a. "Ultrafast spectroscopy of semiconductor nanostructures." Swinburne University of Technology, 2007. http://adt.lib.swin.edu.au./public/adt-VSWT20070426.110438.
Full textGoldmann, Elias [Verfasser], Frank [Akademischer Betreuer] Jahnke, and Gerd [Akademischer Betreuer] Czycholl. "From Structure to Spectra: Tight-Binding Theory of InGaAs Quantum Dots / Elias Goldmann. Gutachter: Frank Jahnke ; Gerd Czycholl. Betreuer: Frank Jahnke." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072225913/34.
Full textProhl, Christopher [Verfasser], Mario [Akademischer Betreuer] Dähne, Holger [Akademischer Betreuer] Eisele, Mario [Gutachter] Dähne, Holger [Gutachter] Eisele, and Philipp [Gutachter] Ebert. "Structural characteristics of InGaAs/GaP quantum dots and related materials on the atomic scale / Christopher Prohl ; Gutachter: Mario Dähne, Holger Eisele, Philipp Ebert ; Mario Dähne, Holger Eisele." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1192370880/34.
Full textNieto, González Luis. "Origem e estabilidade de nanoestruturas de InAs sobre ligas de InP e InGaAs." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278482.
Full textTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Neste trabalho estudamos os mecanismos de crescimento durante a epitaxia por feixe químico de nanoestruturas III-V baseadas no sistema InAs/InP. Particularmente, foram estudados nanofios e ilhas de InAs sobre uma camada buffer InP(001) e nanofios de InAs sobre uma matriz de InGaAs/InP (com mesmo parâmetro de rede). Apresentaremos, nesta tese, as diferenças e similaridades destes sistemas quanto a condições de crescimento, distribuição de tamanho, forma e os efeitos de volume da camada de InGaAs sobre as nanoestruturas de InAs quando comparadas ao sistema InAs/InP. Nossa escolha do InGaAs/InP como camada buffer para a nucleação dos fios de InAs, foi feita porque facilitaria a utilização deste sistema em diversas aplicações, proporcionando maior flexibilidade no desenho dos dispositivos. Por outro lado, este material abre a possibilidade de controlar as características das nanoestruturas através das propriedades de bulk e superficiais da liga ternária InGaAs. Além disso, ligas ternárias podem exibir efeitos de volume que afetam suas propriedades superficiais. Estes fenômenos podem afetar a nucleação dos fios quânticos e por isso foram objeto de nosso estudo. Para isso utilizamos e correlacionamos medidas in situ de difração de elétrons de alta energia (RHEED), microscopia de força atômica (AFM) e eletrônica de transmissão (TEM), com os resultados obtidos por difração de raios X com incidência rasante (GIXD). Verificamos, deste modo, tanto a influência das condições de crescimento, como o comportamento da relaxação da energia elástica nas nanoestruturas. Com todos estes resultados mostramos como acontece a evolução da deformação nos nanofios e pontos quânticos de InAs/InP e como acontecem as transições de forma entre estes dois tipos de nanoestruturas, em função das condições de crescimento e tipo de superfície do substrato utilizado. Mostramos, também que a introdução de um composto ternário (InGaAs) entre o InAs e o InP não afeta significativamente a forma e tamanho das nanoestruturas quando comparadas ao caso InAs/InP. Em particular, a interdifusão gerada por variações locais da composição na camada buffer em nanofios de InAs pode ser minimizada através de mudanças nas condições de crescimento do InGaAs
Abstract: In this work we study the growth mechanisms of III-V nanostructures by chemical beam epitaxy (CBE) based on the InAs/InP materials system. Particularly, nanowires and nanodots of InAs on InP (001) and InAs nanowires on InGaAs/InP (lattice matched) buffer layers were studied. The differences and similarities of these systems are presented in this text, as a function of growth conditions, size distribution, as well as the bulk effects of the InGaAs layer on InAs nanostructures when compared to the InAs/InP system. Our choice of InGaAs/InP buffer layer for InAs nanowire nucleation was due to the possible use of this system in many applications, providing greater flexibility in device design. Furthermore, this material opens up the possibility of controlling nanostructures characteristics through bulk and surface properties of the InGaAs ternary alloy. In other hand, ternary alloys may present volume effects that affect their surface properties. These phenomena can affect quantum wires nucleation and thus became one of the subjects of our study. With these goals in mind, we have correlated in situ high-energy electrons diffraction (RHEED) measurements, atomic force microscopy (AFM) and transmission electron microscopy (TEM) images with the results obtained by grazing incidence X-ray diffraction (GIXD). We report here the influence of the growth conditions on nanostructure shape as well as the behavior of elastic energy relaxation within the nanostructures. Our results show how the evolution of deformation within InAs/InP nanowires and quantum dots occur and how the shape transition between these two types of nanostructures depend on the growth conditions and the substrate surface type used. We also show that the introduction of a ternary compound (InGaAs) between InAs and InP does not significantly affect the shape and size of nanostructures as compared to the InAs / InP case. In particular, the interdifusion generated in InAs nanowires by local variations in the buffer layer composition can be minimized through changes in InGaAs growth conditions
Doutorado
Estrutura de Líquidos e Sólidos; Cristalografia
Doutor em Ciências
Tremblay, Ronan. "Propriétés structurales, optiques et électriques de nanostructures et alliages à base de GaP pour la photonique intégrée sur silicium." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0026/document.
Full textThis PhD work focuses on the structural, optical, electrical properties of GaP-based nanostructures and alloys for integrated photonics on silicon. Amongst the integration approaches of III-V on Si, the interest of GaP/Si is firstly discussed. A study of the growth and the doping of AlGaP used as laser cladding layers (optical confinement and electrical injection) is presented. The activation complexity of n-dopants is highlighted. Then, the photoluminescence properties of InGaAs/GaP quantum dots are investigated as a function of temperature and optical density. The origin of the optical transitions involved are identified as (i) indirect type-I transition between electrons in Xxy states and holes in HH states of quantum dots InGaAs and (ii) indirect type-II with electrons in Xz states of strained GaP. Despite an effective modification in the electronic structure of these emitters, a direct type I optical transition is not demonstrated. This is the major bottleneck in the promotion of GaP based emitters on Si. This said, the control of the GaP/Si interface and electrical injection are confirmed by the demonstration of electroluminescence at room temperature on Si. If no laser effect is obtained in rib laser architectures, a possible beginning of Г band filling in QDs is discussed. Finally, the adequacy of state of the art integrated lasers with the development of on-chip optical interconnects is discussed
Kuntz, Matthias. "Modulated InGaAs/GaAs quantum dot lasers." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=978686241.
Full textPearce, Emma J. "Physics and performance of InGaAs quantum dot lasers." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56033/.
Full textLOPES, ARTUR JORGE DA SILVA. "GROWTH OF QUANTUM DOT TO THE FAMILIES INAS/INP, INAS/INGAAS E INAS/INGAALAS FOR FOTODETECTORS OF INFRARED RADIATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12288@1.
Full textPontos quânticos (PQs) auto-organizáveis de InAs sobre InP, InGaAs, InGaAlAs utilizando-se substratos de InP foram crescidos pela deposição química de metal-orgânicos (MOCVD) e foram investigadas para fotodetectores. Para PQs de InAs crescidos sobre diferentes substratos de InP, têm-se que a presença de discordâncias é responsável pelo aumento na densidade planar dos PQs. O espectro de fotoluminescência (FL) das estruturas de InP/InxGa1-xAs/InAs/InP, com diferentes composições da camada ternária. Medidas com microscopia de força atômica (AFM) mostraram que os PQs mais altos são obtidos quando os mesmos são crescidos sobre uma camada de InxGa1-xAs com um descasamento de 1000ppm, e a altura decresce com o descasamento a partir deste valor. O espectro de FL dos PQs mostrou uma banda assimétrica, a qual envolve transições entre os níveis de energia dos PQs e pode ser decomposta em dois picos. Pico de energia mais alta desta banda foi observado para a amostra com PQs crescidos sobre uma camada de InxGa1-xAs casada e o pico foi deslocado para energias mais baixas para amostras tensionadas. Estruturas diferentes de PQ de InAs crescidas sobre uma camada de InGaAlAs casada com InP foram investigadas. Picos de fotocorrente extremamente estreitos foram observados, demonstrando um excelente potencial para sintonização estreita de comprimentos de onda. Foram desenvolvidas estruturas para detectar radiação superior à 10μm. Medidas de absorção mostrando uma dependência com a polarização mostraram eu as estruturas tem um confinamento total e são apropriadas para detecção sintonizável de radiação por incidência normal.
Self-assembled InAs quantum dots (QD) over an InP, InGaAs, InGaAlAs on InP substrates were grown by metal-organic chemical vapor deposition (MOCVD) and were investigated for quantum dot infrared photodetectors. For InAs QD over an InP buffer on different InP substrates. The results indicate that the presence of dislocations were responsible for the increase in the QD density. Photoluminescence (PL) spectra of InP/InxGa1-xAs/InAs/InP dot-in-a-well structures, with different compositions of the ternary layer. Measurements with atomic force microscopy showed that the largest QD height is obtained when the InAs QDs are grown on the InxGa1-xAs layer with a mismatch of 1000ppm, and the height decreases as the mismatch departs from this value. PL spectra of the QDs showed an asymmetric band, which involves transitions between dot energy levels and can be deconvoluted into two peaks. The highest energy PL peak of this band was observed for the sample with the QDs grown on top of the lattice-matched InxGa1-xAs and it shifted to lower energies for strained samples as the degree of mismatch increased. Different InAs quantum dot structures grown on InGaAlAs lattice matched to InP. Extremely narrow photocurrent peaks were observed, demonstrating great potential for fine wavelenght selection. Structures which can detect radiation beyond 10ìm were developed. Polarization dependence measurements showed that the structures have a zero- dimensional character and are suitable for detection of normal incidence light.
Bhattacharyya, Debabrata. "InGaAs/GaAs self-organised quantum dot lasers : fabrication and characterisation." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301505.
Full textAivaliotis, Pantelis. "New developments in InAs/InGaAs quantum dot-in-a-well infrared photodetectors." Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/10319/.
Full textAndreev, Thomas. "Growth and optical properties of GaN and InGaN quantum dots dops with rare earth ions." Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10020.
Full textThis work reports on structural and optical properties of plasma assisted molecular beam epitaxy grown rare earth doped III – nitride quantum dots structures. During growth the rare earths have drastic influences on the quantum dot formation, assigned to surfactant properties of the rare earth atoms. Optical and structural characterizations have shown that GaN QDs are effectively doped with the rare earth atoms in the cases of Eu, Tm and Tb. Other rare earth locations have been also established, for example for Tm where a high amount has been found at the GaN QDs interface. The excitation dynamics of rare earth doped GaN QDs which show stable photoluminescence for the colors of interest between liquid helium and room temperature has been addressed. More complicate rare earth doped quantum dot structures are also discussed, like InGaN:Eu QDs and co-doped GaN QDs important for devices. Attention is put also onto rare earth doped GaN layers, where different Eu sites have been established, near the sample surface and inside bulk material
Huthmacher, Lukas. "Investigation of efficient spin-photon interfaces for the realisation of quantum networks." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277150.
Full textTan, Hua. "Chirp and Linewidth Characteristics in Semiconductor Quantum Dot Lasers." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258477064.
Full textReid, Benjamin P. L. "Towards cavity quantum electrodynamics and coherent control with single InGaN/GaN quantum dots." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a8d84318-36a8-455f-a2fa-7fb9c4c738a0.
Full textHöglund, Linda. "Growth and characterisation of InGaAs-based quantum dot-in-a-well infrared photodetectors /." Linköping : [Department of Physics, Chemistry and Biology, Linköping University], 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15774.
Full textKatmis, Asli Ugur. "Growth and characterization of InP/In0.48Ga0.52P quantum dots optimized for single-photon emission." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16696.
Full textIn this work the growth of self-assembled InP/InGaP quantum dots, as well as their optical and structural properties are presented and discussed. The QDs were grown on InGaP, lattice matched to GaAs.Self-assembled InP quantum dots are grown using gas-source molecular beam epitaxy over a wide range of InP deposition rates, using an ultra-low growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/μm2 is realized. The resulting isolated InP quantum dots are individually characterized without the need for lithographical patterning and masks on the substrate. Both excitionic and biexcitonic emissions are observed from single dots, appearing as doublets with a fine-structure splitting of 320 μeV. Hanbury Brown-Twiss correlation measurements for the excitonic emission under cw excitation show anti-bunching behavior with an autocorrelation value of g(2)(0)=0.2. This system is applicable as a single-photon source for applications such as quantum cryptography. The formation of well-ordered chains of InP quantum dots on GaAs (001) substrates by using self-organized InGaP surface undulations as a template is also demonstrated. The ordering requires neither stacked layers of quantum dots nor substrate misorientation. The structures are investigated by polarization-dependent photoluminescence together with transmission electron microscopy. Luminescence from the InGaP matrix is polarized in one crystallographic direction due to anisotropic strain arising from a lateral compositional modulation. The photoluminescence measurements show enhanced linear polarization in the alignment direction of quantum dots, [-110]. A polarization degree of 66% is observed. The optical anisotropy is achieved with a straightforward heterostructure, requiring only a single layer of QDs.
Gustafsson, Oscar. "Type-II interband quantum dot photodetectors." Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122294.
Full textQC 20130521
Robinson, James W. "Time-integrated and time-resolved optical studies of InGaN quantum dots." Thesis, University of Oxford, 2005. http://ora.ox.ac.uk/objects/uuid:26101861-dd7f-4cb7-aecf-f482855a3dea.
Full textHatami, Fariba. "Indium phosphide quantum dots in GaP and in In 0.48 Ga 0.52 P." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2002. http://dx.doi.org/10.18452/14873.
Full textThe growth and structural properties of self-assembled InP quantum dots are presented and discussed, together with their optical properties and associated carrier dynamics. The QDs are grown using gas-source molecular-beam epitaxy in and on the two materials InGaP (lattice matched to GaAs) and GaP. Under the proper growth conditions, formation of InP dots via the Stranski-Krastanow mechanism is observed. The critical InP coverage for 2D-3D transition is found to be 3ML for the InP/ InGaP system and 1.8ML for the InP/GaP system. The structural characterization indicates that the InP/GaP QDs are larger and, consequently, less dense compared to the InP/ InGaP QDs; hence, InP dots on GaP tend to be strain-relaxed. The InP/ InGaP QDs tend to form ordered arrays when InP coverage is increased. Intense photoluminescence from InP quantum dots in both material systems is observed. The PL from InP/GaP QDs peaks between 1.9 and 2 eV and is by about 200 meV higher in energy than the PL line from InP/ InGaP QDs. The optical emission from dots is attributed to direct transitions between the electrons and heavy-holes confined in the InP dots, whereas the photoluminescence from a two-dimensional InP layer embedded in GaP is explained as resulting from the spatially indirect recombination of electrons from the GaP X valleys with holes in InP and their phonon replicas. The type-II band alignment of InP/GaP two-dimensional structures is further confirmed by the carrier lifetime above 19 ns, which is much higher than in type-I systems. The observed carrier lifetimes of 100-500 ps for InP/ InGaPQDs and 2 ns for InP/GaP QDs support our band alignment modeling. Pressure-dependent photoluminescence measurements provide further evidence for a type-I band alignment for InP/GaP QDs at normal pressure, but indicate that they become type-II under hydrostatic pressures of about 1.2 GPa and are consistent with an energy difference between the lowest InP and GaP states of about 31 meV. Exploiting the visible direct-bandgap transition in the GaP system could lead to an increased efficiency of light emission in GaP-based light emitters.
Nakagawara, Tanner A. "Optical Spectroscopy of Wide Bandgap Semiconductor Heterostructures and Group-IV Alloy Quantum Dots." VCU Scholars Compass, 2017. https://scholarscompass.vcu.edu/etd/5195.
Full textAriyawansa, Gamini. "Semiconductor Quantum Structures for Ultraviolet-to-Infrared Multi-Band Radiation Detection." Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/phy_astr_diss/17.
Full textTourbot, Gabriel. "Croissance par épitaxie par jets moléculaires et détermination des propriétés structurales et optiques de nanofils InGaN/GaN." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00745125.
Full textChuang, Kuei-ya, and 莊貴雅. "Vertically Coupled InGaAs Quantum Dots." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/42029276965198067316.
Full text國立中山大學
光電工程學系研究所
100
We have investigated the polarization effect of optical process in the vertically coupled InGaAs quantum dots (QDs) triple layers by varying the thickness of GaAs spacer layer. The TE/TM ratio for the ground state emission decreases from near 4 to 1.5 as the spacer thickness (d) decreases from 40 nm to 5 nm. And, the TE polarization (in-plane polarization) is anisotropic with a stronger component along [01-1] direction. P-type modulation doping further decreases the TE/TM ratio to r = 1.2 for the strong vertical coupling QDs structure of 5-nm spacer. Then, using a cross-sectional transmission electron microscopy directly reveals the InGaAs QDs of 5-nm spacer well aligned along the growth direction. From the electroluminescence (EL) and differential absorption (Δα) experiments, the higher optical gain and absorption change for the excited state suggest that the e2-hh transition has higher oscillator strength for the vertically coupled QDs. We also investigate for the triple-layer InGaAs vertically coupled quantum dots (VCQDs) by adding modulation doping (MD) in the 5-nm GaAs spacer layers. In addition to the QDs fundamental and excited transitions, a coupled-state transition is observed for the VCQDs. For the VCQDs of p-type MD, the optical transitions at ground state and coupled state are enhanced by the improvement of hole capture for the valence subbands. For the VCQDs of n-type MD, the main absorption change occurs at the coupled state, consistent with the dominant emission peak observed in EL spectra. For GaAs-based solar cells application, in order to enhance absorption at infrared range for GaAs-based solar cells, multi-stack InGaAs VCQDs of 5-nm GaAs spacers are grown in the active region. Due to the strong vertical coupling between QDs would promote quantum efficiency. We have investigated the photovoltaic response for the solar cells by increasing the layer numbers of VCQDs. The device of nine-layer InGaAs VCQDs shows an enhanced short-circuit current density (Jsc) of 10.5 mA/cm2. The value is increased by 42% compared to GaAs reference device. However, the open-circuit voltage (Voc) is reduced from 0.88 V to 0.54 V. Then, we change the GaAs spacer thickness of coupled In0.75Ga0.25As QDs, and investigated the effects on photovoltaic response. For the sample of d =10 nm shows the best performance of current density (Jsc~24 mA/cm2) and efficiency (h~10.6%). The Jsc and h are increases by 55% and 112% more than the device without QDs, respectively.
Hsing, Jin-Yuan, and 邢晉源. "InGaAs Quantum Dots Microdisk Lasers." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/rbc3pd.
Full text國立中山大學
光電工程學系研究所
101
This thesis describes the fabrication of microdisk lasers that contain gain materials with InGaAs quantum dots. The spontaneous emissions from the specific sizes of quantum dots are enhanced by the whispering gallery modes (WGMs) of the microdisk cavity. First, the lasing wavelength range of InGaAs QDs microdisk cavities is examined. A series of microdisk lasers with diameters that vary in steps of 10 nm from 1.62 μm to 1.86 μm is used, which have a first-order WGM with m=8 enhance the ground state emission of quantum dots in the wavelength range from 1180 nm to 1263 nm. The width of continuous wavelength tuning range is about 80 nm. The lowest threshold power among these QD-containing microdisk lasers is only about 13 μW with a spontaneous emission factor β= 0.674. Second, the bonding and anti-bonding modes of vertically-coupled double microdisk cavities are investigated by utilizing the optical coupling between them. Vertically-coupled double microdisk lasers with three gaps of 100, 200, and 480 nm were fabricated. Room-temperature lasing spectra of the vertically-coupled double microdisks with three gaps but similar diameters around 1.9 μm were obtained. The threshold powers for gaps of 100 nm and 200 nm were approximately 70 μW and 50 μW, respectively. These devices are attractive for use in multiple terahertz light sources based on frequency difference generation. Third, a QD-containing disk cavity is placed on an AlAs/GaAs DBR substrate to develop a mechanically stable current injection structure. The thermo-optical coefficients of AlAs and GaAs for wavelengths around 1200 nm were determined to be 2.2105×10-4 nm/K and 2.8789×10-4 nm/K, respectively. Three emission peaks at 1040 nm, 1090 nm, and 1146 nm were obtained from a DBR-supporting microdisk laser with diameter D=2 μm at T=110 K. These emission peaks were also verified as the first-order WGMs with m=12, 13, and 14. Finally, the emission behaviors of microdisk lasers at T=80 K when a metal nanoparticle is on the top surface of the microdisk cavity are studied. Without the metal NP, the threshold power of the microdisk laser is around 635 μW for the first-order WGM with m=22 at λ=1160 nm. With the metal NP, the threshold power of the microdisk laser is increased to 2.45 mW for the first-order WGM with m=24 at λ=1098 nm.
Tzeng, Kai-Di, and 曾凱迪. "Photovoltaic response of coupled InGaAs quantum dots." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/11947239873527696489.
Full text國立中山大學
光電工程學系研究所
99
The purpose of our research is growing the coupled InGaAs quantum dots on the n-type substrate by molecular beam epitaxy in laboratory, and we choose 5,10 and 15 nanometers to be the thicknesses of GaAs spacer between the quantum dots layer. Due to the couple effect, we hope to realize the theorem of intermediate band proved by Luque and Marti. We measure the characteristic of samples by electroluminescence spectra, photoelectric current spectra, electrical absorption spectra and electro reflectance spectra in laboratory; moreover, we acquire the basic parameters of solar cell by AM1.5G for analyzing. From the basic parameters of solar cell, we know that the quantum dots can enhance the photocurrent by absorbing additional photons , however, the strain caused by quantum dots would decay the open voltage seriously, so that the efficiency always under the baseline. Each efficiency of 9-stack QDs are 4.3%(c494),5.1%(c519),5.3% (c520),and each efficiency of 9-stack Dwells are 3.9%(c524),4.2%(c525),4.7%(c526), and 10-stack QDs(5nm) is 2.9%(c514),and 12-stack QDs(10nm) is 4.48%(c538),and 12-stack QDs(15nm) is 5.89%. The break through of this paper is that the efficiency of c529(VOC=0.64V,JSC=11.97mA/cm2,FF=67%,η=5.89%)is higher than GaAs(VOC =0.87 V, JSC =7.4 mA/cm2,FF=72.3%,η=5.6%),and we attribute this performance to its good quality of miniband, because the current can be enhanced a lot, and it will make up for the lose of open voltage and filling factor, so that the efficiency can be higher than GaAs baseline.
Tzeng, Te-En, and 曾德恩. "InGaAs Quantum Dots grown by Molecular Beam Epitaxy." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/90197754181344616147.
Full text國立中山大學
光電工程學系研究所
99
In this thesis, we have reported the MBE growth, design, and fabrication of the InGaAs quantum dots (QDs) laser/semiconductor optical amplifier, broadband QDs structure, coupled double cavity structure for terahertz emission on GaAs substrate. The emission wavelengths of the strain-induced S-K growth mode QDs structures are adjusted through the composition of QDs and strain-compensated capping layer. Also, the technique of growing high quality InGaAs QDs with solid source molecular beam epitaxy has been established and characterized by double crystal X-ray diffraction, transmission electron microscopy, photoluminescence, electroluminescence measurements. For 1.3μm QDs laser samples, ridge waveguide lasers of the Fabry-Perot (FP) type are fabricated by wet-etching process. From the QDs laser L-I curve, the e2-hh2 transition at λ =1160nm have larger optical gain than e1-hh1 transition at λ =1220nm. The FP laser with 0.6μm cavity length shows a lasing peak of 1160nm at threshold. As the cavity length increase to 2μm, the lasing peak red shift to 1220nm (closed to ground state emission wavelength). This energy band gap transition phenomenon is obvious especially in the QDs laser with quantum well (QW) structure. When the injection current increase, two lasing peaks at λ= 1160 and 1175nm are observed sequentially. This unique lasing behavior is shown to be consistent with carriers localized in noninteracting dots. For the application of 1.3μm light source, we optimum the growth condition for different needs in optical coherent tomography (OCT) light source, tandem solar cell, terahertz emission light source, etc. For the super luminescence diode (SLED) in OCT, we design multi-stacked asymmetric QDs structure (AMQD), QDs in the well structure (DWell), Dwell with p-doping in well structure to investigate the carrier recombination condition and bandwidth. Comparing with 5 structures in this study, the Dwell with p-doping in well structure has a maximum EL bandwidth exceed 198nm. The large bandwidth is attributed to the QW which increases the carrier capture rate and the p-doping which provide the efficient holes in valance band. This structure provides an excellent SLED light source solution to replace the existing program. For the tandem solar cell, we use the multi-stack QDs to compose broadband absorption in 1eV range. In order to avoid the degradation in the open circuit voltage, we use InGaAs QW to reduce the QDs strain. We observed the doping effect on the built in field through the photo-reflectance measurements. For the better photocurrent collection, we use p-doping in the QW to increase the built-in field intensity to obtain higher efficiency. For the terahertz emission, the QDs embedded in coupled double-cavity structures with an AlAs/GaAs intermediate distributed Bragg reflector (DBR) are grown on GaAs substrates. Two emission peaks at 1180, 1206 nm from the QDs corresponding to the coupled double-cavity resonant modes are observed in the high reflection band. The frequency differences for the two resonant coupled modes are of 5.5 terahertz, and have been successfully controlled by changing the pair numbers for the intermediate DBR. In addition, we have grown the InGa(Al)As nanostructures on InP substrate. The lattice constant difference between InGaAs and InP is relatively smaller compare with GaAs substrate, and it will be more challenge in epitaxial growth. After we investigate the strain, surface morphologies, optical properties for the nanostructures, we find the group III elements play an important role in the morphologies. Wire formation is attributed by the enhanced adatom diffusion length in the stepped surface front along [0-11] direction for the presence of Ga both in the nanostructure and buffer layer. Finally, we established QDs, Qwires database for the valuable new possibilities for designing new and original structures.
Wei, Sun-Yong, and 魏孫詠. "Raman Spectroscopy on InGaAs Quantum Dots in Coupled Cavity." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/10397759345788956392.
Full text國立中興大學
光電工程研究所
104
The epitaxy InGaAs quantum dot of molecular beam epitaxy on the Bragg reflector is utilized for measuring Raman Spectroscopy and analyzing the relative signal strength and wave number position(GaAs :To mode and Lo mode、InGaAs QDs). First, InGaAs quantum dots present the characteristic of tunable band gap that the contents of In and Ga are changed for growing the stack layer with different band gap so as to measure the Raman spectra of In and Ga under distinct proportion. As a single-layer quantum dot shows small signal strength, we try surface-enhanced Raman scattering (SERS)to coat a thin layer of Au (about 10nm) on the sample, with thermal evaporator, for annealing. Gold nanoparticles would be self-assembly method to reinforce the signal strength, or gold nanoparticles are directly spin coated on the sample. The result reveals slightly different measurement results of InGaAs under different dimension. Finally, the Raman spectra of the coupled cavity sample are measured. The top and the bottom are connected with a Bragg reflector and two pairs of quantum dots and a set of Bragg reflector is inserted in the middle. The transmission shows that the transmission peak coupled with 13.5 pairs of DBR and 23.5 pairs of DBR is too close to separate two transmission peak, while inserting 6.5 pairs could improve such a problem. Furthermore, micro-photoluminescence and Raman spectra are used for cross-analyzing the quantum dot Raman spectra effect as the region. It is measured that the quantum dot under vertical coupling appears larger Raman signals than the single-layer quantum dot. Besides, the Raman spectra reveal that the back-end process would damage the sample structure because of high temperature. It is expected to introduce Raman spectra as the rough estimated coupled cavity sample structrure.