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1
Mohammed, Ali Mohammed Jassim. "Optical characterisation of non polar nanostructures quantum wells ZnO/(Zn,Mg) O." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS096/document.
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L’oxyde de zinc est un matériau prometteur pour la réalisation de composants optoélectroniques dans la gamme des émetteurs UV. Pour cela il faut développer des hétéro-structures tel que des puits quantiques ZnO/(Zn, Mg)O afin de mieux contrôler les propriétés d’émissions. Ce travail porte sur la caractérisation de telles structures crûes sur le plan A, surface non polaire, de ZnO massif. A partir de mesures de spectroscopie optiques (réflectivité, photoluminescence en excitation continue et photoluminescence résolue en temps) nous avons déterminé les différents phénomènes physiques mis en jeux lors de la recombinaison radiative des porteurs dans ces puits quantiques. Dans un premier temps, nous avons étudié en détail l’émission des photons par les barrières de (Zn, Mg)O. Grace à l’étude en température nous avons montré que l’émission optique de la barrière correspond à la recombinaison de paires électron trou en interactions (excitons) qui sont à basses températures localisées dans des fluctuations de potentiel. Sous l’effet de la température ils se délocalisent et se recombinent comme des exciton libres. L’étude détaillée des déclins temporels de photoluminescence nous à permis de démontrer que nous avions affaire à deux états excitoniques différents qui présentent des dynamiques de recombinaisons différentes. Un modèle est proposé pour rendre compte des différentes observations. La partie principale de ce travail porte sur le comportement des excitons dans le puits quantique. Le résultat majeur de cette étude est la démonstration expérimentale que dans ce cas des complexes excitoniques, ici des trions chargé négativement (exciton en interaction avec un électron libre), se forment à basse température et sont responsable de la luminescence observée. De plus, en variant la densité d’excitation nous avons montré que se former également des bi-excitons (pseudo particule formée de deux exciton en interactions). Le comportement en température de la photoluminescence obtenue dans différente conditions d’excitation à permis de démontrer que sous l’effet de l’énergie thermique les complexes excitoniques se dissociés pour créer des excitons libres. Des mesures en fonction de la polarisation de la lumière émise et de la température ont permis également d’étudier l’état C de l’exciton dans le puits. Les dynamiques de recombinaison des différents complexes excitoniques sont examinées en fonction de la températureThe zinc oxide is a promising material for the realization of optoelectronic devices in the blue-UV range. For this, it is necessary to develop hetero-structures such as ZnO / (Zn, Mg) O quantum wells in order to have better control of the properties of emissions. This work concerns the characterization of such structures grown on the A-plane (non-polar surface) of bulk ZnO. From optical spectroscopies measurements (reflectivity, continuous wave and time-resolved photoluminescence) we determined the various physical phenomena involve during the radiative recombination of the carriers in these quantum wells. At first, we studied in detail the emission of photons by the barriers of (Zn, Mg) O. Thanks to the study in temperature we showed that the optical emission of the barrier corresponds to the recombination of electron hole pairs in interactions (excitons), which are at low temperatures localized in the fluctuations of the potential. Under the influence of the temperature they delocalize and recombine as free exciton. From the detailed study of the temporal decays of photoluminescence we can demonstrate that we deal with two different excitonic states, which present different dynamics of recombination. A model is proposed that explain the various observations. The main part of this work concerns the behavior of the excitons in the quantum well. The major result is the experimental demonstration that excitonics complexes are formed at low temperature, negatively charged trion (exciton in interaction with a free electron), in this system and they are responsible for the observed luminescence. Furthermore, by varying the density of excitation we showed that biexcitons are also form (pseudo-particles formed by two excitons in interactions). The behavior in temperature of the photoluminescence obtained in different conditions of excitation demonstrates that under the influence of the thermal energy the exitonic complexes are broken to create free excitons. Measures according to the polarization of the emitted light and the temperature also allowed studying the C state of the exciton in the quantum well. The dynamics of recombination of the various excitonics complexes are examined according to the temperature
2
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.
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Semiconductor nanostructures exhibit many remarkable electronic and optical properties.
The key to designing and utilising semiconductor quantum structures is a physical understanding
of the detailed excitation, transport and energy relaxation processes. Thus the nonequilibrium
dynamics of semiconductor quantum structures have attracted extensive attention in recent years.
Ultrafast spectroscopy has proven to be a versatile and powerful tool for investigating transient
phenomena related to the relaxation and transport dynamics in semiconductors.
In this thesis, we report investigations into the electronic and optical properties of various
semiconductor quantum systems using a variety of ultrafast techniques, including up-conversion
photoluminescence, pump-probe, photon echoes and four-wave mixing. The semiconductor
quantum systems studied include ZnO/ZnMgO multiple quantum wells with oxygen ion
implantation, InGaAs/GaAs self-assembled quantum dots with different doping, InGaAs/InP
quantum wells with proton implantation, and silicon quantum dots. The spectra of these
semiconductor nanostructures range from the ultraviolet region, through the visible, to the
infrared. In the UV region we investigate excitons, biexcitons and oxygen implantation effects in
ZnO/ZnMgO multi-quantum wells using four-wave mixing, pump-probe and photoluminescence
techniques. Using time-resolved up-conversion photoluminescence, we investigate the relaxation
dynamics and state filling effect in InGaAs self-assembled quantum dots with different doping,
and the implantation effect in InGaAs/InP quantum wells. Finally, we study the optical properties
of silicon quantum dots using time-resolved photoluminescence and photon echo spectroscopy on
various time scales, ranging from microseconds to femtoseconds.
3
Perillat-Merceroz, Guillaume. "Mécanismes de croissance et défauts cristallins dans les structures à nanofils de ZnO pour les LED." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI053/document.
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Les nanofils de ZnO à puits quantiques et le dopage p par implantation ionique d'azote sont étudiés pour la fabrication de LED ultra-violettes. Des pyramides de polarité O et des nanofils de polarité Zn sur substrats de saphir et ZnO sont élaborés. La croissance organisée de nanofils sur ZnO de polarité Zn est démontrée. De même, des pyramides ou des nanofils de GaN sont obtenus sur GaN de polarité Ga ou N. Sur saphir, l'élimination des dislocations dans les pyramides sous-jacentes aux nanofils est analysée. Les nanofils sans défauts structuraux permettent l'élaboration de puits quantiques coeur-coquille ZnO/Zn(1-x)MgxO. La relaxation plastique dans les nanofils est étudiée, puis la composition en Mg est optimisée pour l'éviter et atteindre un rendement quantique interne de 54%. Concernant l'implantation, les défauts sont identifiés avant et après recuit. Ils disparaissent en surface, d'où une guérison facilitée des nanofils. Un matériau guéri avec des accepteurs activés n'est pas obtenuQuantum well ZnO nanowires and p-type doping by nitrogen ion implantation are studied to make ultraviolet light-emitting diodes. O-polar pyramids and Zn-polar nanowires on sapphire and ZnO substrates are grown. Organized growth of nanowires on a masked Zn-polar ZnO is demonstrated. Similarly, GaN pyramids and nanowires are grown on Ga and N-polar GaN respectively. On sapphire, the dislocation elimination in the underlying pyramids is analyzed. Nanowires with no structural defects allow the growth of ZnO / Zn (1-x) Mg x O core-shell quantum wells. Plastic relaxation is studied, and the Mg composition is optimized to avoid it and attain an internal quantum efficiency as high as 54%. Concerning ion implantation, the defects are identified before and after annealing. They disappear in the near-surface, which lead to an easier recovery of nanowires compared to bulk ZnO. However, a recovered material with activated acceptors is not obtained
4
Jollivet, Arnaud. "Dispositifs infrarouges à cascade quantique à base de semiconducteurs GaN/AlGaN et ZnO/ZnMgO." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS058/document.
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Ce mémoire de thèse est consacré à l’étude et au développement des hétérostructures semi-conductrices à base de GaN et ZnO. Ces matériaux sont particulièrement prometteurs pour le développement de composants optoélectroniques inter-sous-bandes infrarouges et notamment pour les dispositifs à cascade quantique. Ces semiconducteurs possèdent en effet plusieurs avantages pour la conception de dispositifs à cascade, tels qu’une grande discontinuité de potentiel en bande de conduction et une énergie du phonon LO très élevée. Ces propriétés se traduisent par la possibilité de développer des dispositifs couvrant une gamme spectrale allant du proche-infrarouge au térahertz et offrent la possibilité de réaliser des lasers à cascade quantique térahertz fonctionnant à température ambianteThis manuscript focuses on the study and on the development of semiconductor heterostructures based on GaN and ZnO material. These materials are particularly promising for the development of infrared optoelectronic intersubband devices in particular for quantum cascade devices. These semiconductors own several advantages to design quantum cascade devices such as a large conduction band offset and a large energy of the LO phonon. These properties predict the possibility to develop devices covering a large spectral range from near-infrared to terahertz and offer the possibility to realize terahertz quantum cascade lasers operating at room temperature
5
Chieh-Yi, Kuo. "Fabrication and Optical Properties of ZnO Nanocrystal/GaN Quantum Well Based Hybrid Structures." Thesis, Linköpings universitet, Tunnfilmsfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-81675.
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Optical properties of hybrid structures based on zinc oxide nanocrystals (NCs) and Gallium Nitride quantum well (QW) has been studied. The ZnO NCs thin films on the top of GaN QW structures were fabricated using spin coating. The surface morphology was characterized by scanning electron microscopy (SEM). We have performed temperature dependence time-resolved photoluminescence (TRPL) measurements of the bare AlGaN/GaN QW structures and hybrids, containing ZnO NCs. It was found that at some temperatures the QW PL decay has shorter decay time in the presence of ZnO NCs thin film compared to the bare QW. The effect was stronger for the samples with thinner cap layers. The results are discussed in terms of three models such as exciton nonradiative energy transfer (NRET), tunneling effect, and piezoelectric field influence on the QW exciton energy.
6
Shastri, Vasant. "Excitonic and Raman properties of ZnSe/Zn1-xCdxSe strained-layer quantum wells." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1173325694.
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Stölzel, Marko. "Photolumineszenz von Exzitonen in polaren ZnO/MgZnO-Quantengrabenstrukturen." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-147166.
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Die vorliegende Arbeit befasst sich mit dem vertieften Verständnis der Rekombinationsdynamik von polaren ZnO/MgZnO-Quantengraben(QW)-Strukturen zur exakten Bestimmung des unabgeschirmten Grundzustandes und der Analyse der zugrundeliegenden Emissionsprozesse. Dafür werden ausgehend von Beobachtungen an ZnO-Dünnschichten die Eigenschaften von mittels PLD hergestellten QWs unter dem Einfluss des internen elektrischen Feldes mit Hilfe der zeitintegrierten (TI-) und zeitaufgelösten (TR-) Photolumineszenz(PL)-Spektroskopie untersucht.
Die Differenz der spontanen und piezoelektrischen Polarisation zwischen ZnO und MgZnO führt zur Ausbildung eines internen elektrischen Feldes und damit zum Auftreten des quantum-confined Stark effect (QCSE). Es wird gezeigt, dass der QCSE durch eine Durchmischung der Grenzflächen stark vermindert wird. Für QWs mit schwachem QCSE ist die Übergangsenergie und Zerfallszeit des Grundzustandes experimentell gut bestimmbar. Bei starkem QCSE müssen jedoch bereits bei geringen Anregungsdichten (1E10 /cm²) Abschirmeffekte berücksichtigt werden. Dadurch ist es sehr schwierig, den unabgeschirmten Grundzustand mittels herkömmlicher experimenteller Methoden mit einem aussagekräftigen Signal-Rausch-Verhältnis zu bestimmen. Es wird gezeigt, dass für QWs mit einer Dicke > 4 nm die Übergangsenergie des unabgeschirmten Grundzustandes nicht durch TI-PL-Messungen bestimmt werden kann. TR-PL-Messungen zeigen energetisch tiefere Übergangsenergien, jedoch ebenfalls nicht den unabgeschirmten Grundzustand. Mit einem eingeführten Modell zur Beschreibung der zeitabhängigen Abschirmung des Grundzustandsniveaus wird die Zerfallszeit für QW-Dicken in einem Bereich von 1 - 10 nm bestimmt. Durch die selbstkonsistente Lösung von Schrödinger- und Poissongleichung werden die Übergangsenergie und Zerfallszeit der Exzitonen im QW in Abhängigkeit der Feldstärke und auch der Ladungsträgerdichte berechnet. Dadurch ist eine exaktere Bestimmung der Feldstärke möglich. Zusätzlich wird durch die vergleichende Untersuchung von QWs unterschiedlicher Dicke, Potentialhöhe und Wachstumsunterlage die spontane und piezoelektrische Polarisation der Materialien experimentell bestimmt.
Mittels temperaturabhängiger Messungen wird der Ursprung der Lumineszenz für QW-Dicken > 2 nm der Rekombination freier Exzitonen im QW zugeschrieben. Für dünnere QWs ist der temperaturabhängige Verlauf des PL-Maximums durch Lokalisation der Exzitonen bestimmt.
8
Howari, Haidar. "Pulsed laser annealing of CdTe/Cd1-xMnxTe epilayers and pulsed laser emission of ZnS/Zn1-xCdxS quantum well structures." Thesis, University of Hull, 1999. http://hydra.hull.ac.uk/resources/hull:8297.
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Shastri, Vasant K. "Excitonic and Raman properties of ZnSe/Zn 1-xCd xSe strained-layer quantum wells." Ohio University / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173325694.
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Sadofiev, Sergey. "Radical-source molecular beam epitaxy of ZnO-based heterostructures." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/16054.
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Im Rahmen der Dissertation wurden molekularstrahlepitaktische Verfahren zur Züchtung von Hetero-und Quantenstrukturen auf der Basis der Gruppe II-Oxide entwickelt. Insbesondere wurde ein Wachstumsregime weit entfernt vom thermischen Gleichgewicht etabliert, welches die Mischung von CdO und MgO mit ZnO in phasenreiner Wurtzitstruktur ermöglicht, wobei die Gleichgewichtslöslichkeitsgrenzen dramatisch überschritten werden. In den Mischkristallen kann die Bandlücke kontinuierlich von 2.2 bis 4.4 eV eingestellt werden. Das Wachstum verläuft in einem zweidimensionalen Modus und resultiert in atomar glatten Ober- und Grenzflächen. Ausgeprägte RHEED- Intensitätsoszillationen erlauben die atomlagengenaue Kontrolle der Schichtdicken und somit die Realisierung wohl-defi- nierter Einzel- und Mehrfachquantengrabenstrukturen. Diese zeichnen sich durch eine hohe Photolumineszenzquantenausbeute im gesamten sichtbaren Spektralbereich aus. Laseraktivität kann vom UV bis zum grünen Wellenlängenbereich bei Zimmertemperatur erzielt werden. Das Potenzial dieser Quantenstrukturen in Hinblick auf ihre Anwendung in opto-elektronischen Bauelementen wird diskutiert.This work focuses on the development of the novel growth approaches for the fabrication of Group II-oxide materials in the form of epitaxial films and heterostructures. It is shown that molecular-beam epitaxial growth far from thermal equilibrium allows one to overcome the standard solubility limit and to alloy ZnO with MgO or CdO in strict wurtzite phase up to mole fractions of several 10 %. In this way, a band-gap range from 2.2 to 4.4 eV can be covered. A clear layerby- layer growth mode controlled by oscillations in reflection high-energy electron diffraction makes it possible to fabricate atomically smooth heterointerfaces and well-defined quantum well structures exhibiting prominent band-gap related light emission in the whole composition range. On appropriately designed structures, laser action from the ultraviolet down to green wavelengths and up to room temperature is achieved. The properties and potential of the "state-of-the-art" materials are discussed in relation to the advantages for their applications in various optoelectronic devices.
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Marotel, Pascal. "Spectroscopie optique de l'oxyde de zinc." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00647305.
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Ce travail porte sur l'étude des propriétés optiques de l'oxyde de zinc (ZnO), matériau semi-conducteur à grand gap. La technique de caractérisation principale de ce travail est la spectroscopie par photoluminescence, technique non destructive permettant d'obtenir des informations relatives à la structure électronique d'un matériau. Après avoir présenté les propriétés du ZnO, de ses alliages, et rappelé quelques principes de base associés à la luminescence des matériaux semi-conducteurs., nous comparerons dans un premier temps les propriétés optiques de différents types de ZnO monocristallin, selon leur mode d'élaboration : matériaux massifs de différentes origines, couches épitaxiées et nanofils. Ces comparaisons ainsi que l'étude des effets sur les spectres de photoluminescence des traitements tels que recuit et passivation nous permettront d'avancer différentes hypothèses quant à l'origine de la luminescence visible dans ce matériau grand gap, sujet encore controversé dans la littérature. Dans un deuxième temps, nous présenterons notre contribution à l'étude du dopage p du matériau, qui est encore aujourd'hui le verrou pour l'obtention de diodes électroluminescentes à base de ZnO. Nous examinerons le problème du dopage intrinsèque de type n et de la compensation, préalable indispensable avant d'aborder le dopage de type p. Le dopage p est traité ici principalement au travers des études optiques d'échantillons implantés et recuits. Plusieurs variantes liées à l'implantation d'azote seront présentées et l'obtention de paires donneur accepteurs clairement mise en évidence pour des conditions de recuit optimisées. La nature des accepteurs présents est discutée par référence aux travaux antérieurs. .
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Lin, Jie (physicist). "Interaction of Plasmons and Excitons for Low-Dimension Semiconductors." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc799475/.
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The effects of surface plasmon for InGaN/GaN multi-quantum wells and ZnO nanoparticles optical linear and nonlinear emission efficiency had been experimentally studied. Due to the critical design for InGaN MQWs with inverted hexagonal pits based on GaN, both contribution of surface plasmon effect and image charge effect at resonant and off resonant frequencies were experimentally and theoretically investigated. With off- resonant condition, the InGaN MQWs emission significantly enhanced by metal nanoparticles. This enhancement was caused by the image charge effect, due to the accumulation of carriers to NPs region. When InGaN emission resonated with metal particles SP modes, surface Plasmon effect dominated the emission process. We also studied the surface plasmon effect for ZnO nanoparticles nonlinear optical processes, SHG and TPE. Defect level emission had more contribution at high incident intensity. Emissions are different for pumping deep into the bulk and near surface. A new assumption to increase the TPE efficiency was studied. We thought by using Au nanorods localized surface plasmon mode to couple the ZnO virtual state, the virtual state’s life time would be longer and experimentally lead the emission enhancement. We studied the TPE phenomena at high and near band gap energy. Both emission intensity and decay time results support our assumption. Theoretically, the carriers dynamic mechanism need further studies.
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Lange, Martin. "Herstellung und Charakterisierung von planaren und drahtförmigen Heterostrukturen mit ZnO- und ZnCdO-Quantengräben." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-104504.
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Im Rahmen der vorliegenden Arbeit wurden planare und drahtförmige Heterostrukturen (HS) mit ZnO- und ZnCdO-Quantengräben bezüglich ihrer Lumineszenz untersucht. Die Proben wurden mit der gepulsten Laserabscheidung (PLD) hergestellt. Bei ZnO-basierten drahtförmigen HS mit Durchmessern im Mikro- und Nanometer-Bereich handelt es sich um vielversprechende Kandidaten für miniaturisierte optoelektronische Bauelemente.
Da es für viele Anwendungen notwendig ist, dass die Emission des Quantengrabens (QW) in einem breiten Spektralbereich eingestellt werden kann, muss die ZnO-Bandlücke möglichst stark verändert werden können. Durch ZnCdO und MgZnO ist dies möglich. Durch eine Optimierung der Abscheideparameter wurde der für PLD erreichte maximale Cd-Gehalt signifikant auf 0,25 erhöht. Große Mg-Gehalte konnten schon vor der Forschung zur vorliegenden Arbeit mit der PLD realisiert werden.
Die planaren HS mit ZnO-Quantengräben wurden vorrangig bezüglich Ihrer Lumines-zenzeigenschaften untersucht. Aufgrund der Orientierung der QW sollten diese zusätzlich zum Quantum-Confinement Effekt den Quantum-Confined Stark Effect (QCSE) zeigen. Der QCSE wurde durch zeitabhängige und anregungsabhängige Lumineszenzmessungen nachgewiesen. In den Mikrodraht (µW)- bzw. Nanodraht (NW)-HS mit ZnO-QW wurde die Emission zwischen 3,4 eV und 3,6 eV bzw. 3,4 eV und 3,7 eV eingestellt.
Um HS mit ZnCdO-QW herstellen zu können, war es notwendig, die strukturellen und optischen Eigenschaften sowie die elektronische Struktur von ZnCdO-Dünnfilmen zu untersuchen. Durch einen hohen Cd-Gehalt von 0,25 war es möglich, die Bandlücken-energie um 0,8 eV zu verringern. In planaren HS wurde ZnO bzw. MgZnO als Barriere verwendet und die QW-Emission zwischen 2,5 eV und 3,1 eV bzw. 2,5 eV und 3,65 eV eingestellt. Es wurde untersucht, ob für HS mit ZnCdO-QW ein QCSE auftritt. Die experimentellen Energien wurden dazu mit berechneten Werten verglichen, die mithilfe einer Effektiv-Masse-Näherung und dem Modell eines endlich tiefen Potentialtopfes bestimmt wurden. In entsprechenden µW- bzw. NW-HS wurde die QW-Emission infolge des Quantum-Confinement Effektes zwischen 2,7 eV und 3,1 eV bzw. 2,5 eV und 3,4 eV variiert.
Da es für die Anwendung von µW- und NW-HS wichtig ist, dass diese eine homogene QW-Emission zeigen, wurde deren spektrale Position entlang der Struktur und für die verschiedenen Facetten der hexagonalen Drähte untersucht. Die Homogenität der Emission
ist für die µW-HS kleiner als für die NW-HS.
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Li, Tiesheng. "Optical properties of CdTe/Cd1-xZnxTe strained-layer single quantum wells." Ohio University / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173760803.
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Stölzel, Marko, Alexander Müller, Gabriele Benndorf, Michael Lorenz, Christian Patzig, Thomas Höche, and Marius Grundmann. "Determination of the spontaneous polarization of wurtzite (Mg,Zn)O." American Institute of Physics, 2014. https://ul.qucosa.de/id/qucosa%3A26869.
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We report on the experimental determination of the spontaneous polarization of wurtzite-
(Mg,Zn)O by examination of the recombination dynamics of polar ZnO/(Mg,Zn)O quantum wells
(QWs). The thickness-dependent decay time of the unscreened single-exciton states inside the
QWs was modeled by a self-consistent solution of Schrödinger- and Poisson-equation to deduce
the total polarization across the QW for different Mg-contents inside the barriers. By the separation
of the piezoelectric components of the polarization, a linear increase in spontaneous polarization
with increasing Mg-content x of P/x = (0.151 ± 0.015) C/m2 was determined for Mgx Zn1−x O.
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Venturi, Linda. "Etude des propriétés de photoluminescence de nano-matériaux sous champ électrique intense." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR118.
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Dans cette thèse, la tomographie à sonde atomique assistée par laser est couplée in situ à un banc de photoluminescence (PL), où le rayonnement laser pulsé est utilize pour déclencher l’évaporation ionique des échantillons et, simultanément, pour activer l’émission à partir des centres optiquement actifs présents dans le matériau. Pour ce travail, deux matériaux différents ont été sélectionnés : des nano-aiguilles de diamant avec des défauts optiquement actifs intégrés (centres de couleur) et une hétérostructure multi-quantique (MQW) ZnO / (Mg, Zn)O, qui contient des émetteurs quantiques d’épaisseurs différentes. Grâce à cette configuration originale de photoluminescence, l’influence du champ électrique sur la structure fine de certains centres de couleur, noyés dans les nano-aiguilles de diamant, a été observée. La première étude s’est concentrée sur le centre neutre de vacance d’azote (NV0), qui est l’un des centres de couleur les plus étudiés dans la littérature. L’évolution de la signature optique NV0, en fonction du biais appliqué, a permis d’évaluer la contrainte mécanique (> 1 GPa) et le champ électrique agissant sur les pointes de diamant. Ces résultats démontrent une nouvelle méthode originale pour effectuer la piezo-spectroscopie sans contact des systems nanométriques sous une contrainte de traction uniaxiale, générée par le champ électrique. Cette méthode a également été appliquée à un autre centre de couleur, dont la nature n’est toujours pas claire dans la littérature, émettant à 2,65 eV, et plus sensible que les centres de couleur NV0 au champ de contrainte / déformation. Des nouveaux résultats sur ses propriétés opto-mécaniques ont été obtenus, mais son identité reste à comprendre. Le champ d’évaporation du diamant étant très élevé, les nano-aiguilles de diamant n’ont pas été analysées à l’aide de La-APT. Par conséquent, la technique couplée in situ a été appliquée afin d’étudier l’hétérostructure ZnO / (Mg, Zn) O MQW, en accédant à la structure, à la composition et à la signature optique de l’échantillon sondé dans une seule expérience. Les spectres de photoluminescence acquis par le spécimen au cours de son évaporation en cours représentent une source unique d’informations pour la compréhension du mécanisme de l’interaction lumière-matière et la physique de la photoémission sous champ électrique élevé. La corrélation des informations structurelles et optiques, liées à cette hétérostructure MQW, démontre que la technique couplée in situ peut chevaucher la limite de diffraction du laser PL et que, comme pour les nano-aiguilles de diamant, il est possible d’estimer le stress de traction induit. Les résultats obtenus par couplage in situ de la technique La-APT avec la spectroscopie PL montrent qu’un tel instrument est une technique innovante et puissante pour effectuer des recherches à l’échelle nanométrique. Pour cette raison, ce travail peut ouvrir de nouvelles perspectives pour une compréhension approfondie de la physique liée aux systèmes étudiés en parallèle avec l’amélioration continue de la configuration expérimentaleIn this thesis, the Laser-assisted Atom Probe Tomography is coupled in-situ with a photoluminescence (PL) bench, where the pulsed laser radiation is used to trigger the ion evaporation from the specimens and, simultaneously, to activate the emission from optically active centers present into the material. For this work, two different materials were selected: diamond nano-needles with embed- ded optically active defects (color centers) and a ZnO/(Mg,Zn)O multi-quantum-well (MQW) heterostructure, which contains quantum emitters of different thicknesses. Thanks to this original photoluminescence setup, the influence of the electric field on the fine structure of some color centers, embedded into the diamond nanoneedles, was observed. The first study focused on the neutral nitrogen-vacancy center (NV0), which is one among the most studied color centers in literature. The evolution of the NV0 optical signature, as a function of the applied bias, allowed to evaluate the mechanical stress (> 1 GPa) and the electric-field acting on diamond tips. These results demon- strate an original new method to perform contactless piezo-spectroscopy of nanoscale systems under uniaxial tensile stress, generated by the electric field. This method was applied also on another color center, which nature is still not clear in literature, emitting at 2.65 eV, and more sensitive than the NV0 color centers to the stress/strain field. New results on its opto-mechanical properties were obtained, but its identity still needs to be understood. Since the evaporation field of diamond is really high, the diamond nanoneedles were not analyzed using La-APT. Therefore the coupled in-situ technique was applied in order to study the ZnO/(Mg,Zn)O MQW heterostructure, accessing to the structure, composition and optical signature of the probed specimen in only one experiment. The photoluminescence spectra acquired by the specimen during its ongoing evaporation represents a unique source of information for the understanding of the mechanism of light-matter interaction and the physics of photoemission under high electric field. The correlation of the structural and optical information, related to this MQW heterostructure, demonstrates that the coupled in-situ technique can overlap the diffraction limit of the PL laser and that, as done for the diamond nanoneedles, is pos- sible to estimate the induced-tensile-stress. The results achieved by the in-situ coupling of the La-APT technique with the PL spec- troscopy show that such instrument is an innovative and powerful technique to perform research at the nanometric scale. For this reason, this work can open new perspectives for a deeply understanding of the physicics related to the studied systems in parallel with the continuous enhancement of the experimental setup
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Zippel, Jan. "Gepulste Laserabscheidung und Charakterisierung funktionaler oxidischer Dünnfilme und Heterostrukturen." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-100358.
Full textAbstract:
In der vorliegenden Arbeit wird das Hauptaugenmerk auf die Untersuchung der Auswirkungen einer Modifikation der zugänglichen Prozessparameter auf die funktionalen Eigenschaften oxidischer Dünnfilme während der gepulsten Laserabscheidung (PLD) gelegt.
Der erste Teil der Arbeit stellt die Herstellung von BaTiO3/SrTiO3-Mehrfach-Heterostrukturen auf thermisch und chemisch vorbehandelten SrTiO3-Substraten mittels gepulster Laserabscheidung (PLD) vor. Die zugängliche in-situ Wachstumskontrolle durch ein reflection high-energy electron diffraction (RHEED)-System ermöglicht es die Wachstumsprozesse in Echtzeit zu überwachen. Angestrebt wird ein stabiler zwei-dimensionaler Wachstumsmodus, der neben glatten Grenzflächen auch eine hohe Dünnfilmqualität ermöglicht. Es wird erstmals die prinzipielle Anwendbarkeit von BaTiO3/SrTiO3-Heterostrukturen als Bragg-Spiegel aufgezeigt. Für BaTiO3- sowie SrTiO3-Dünnfilme wurden die PLD-Parameter Substrattemperatur, Sauerstoffpartialdruck, Energiedichte des Lasers sowie Flussdichte der Teilchen variiert und die Auswirkungen auf die strukturellen, optischen und Oberflächeneigenschaften mittels Röntgendiffraktometrie (XRD), spektraler Ellipsometrie (SE) und Rasterkraftmikroskopie (AFM) beleuchtet.
Im zweiten Teil werden ZnO/MgxZn1−xO-Quantengrabenstrukturen hetero- und homoepitaktisch auf thermisch vorbehandelten a-Saphir- respektive m- und a-orientierten ZnO-Einkristallen vorgestellt. Die Realisierung eines zwei-dimensionalen „layer-by-layer“ Wachstumsmodus wird für die Quantengrabenstrukturen aufgezeigt. Die Quantengrabenbreite lässt sich aus beobachteten RHEED-Oszillationen exakt bestimmen. Ein Vergleich zwischen, mittels Photolumineszenz gemessenen Quantengrabenübergangsenergien als Funktion der Grabenbreite mit theoretisch ermittelten Werten wird vorgestellt, wobei der Unterschied zwischen polaren und nicht-polaren Strukturen mit Blick auf eine Anwendung aufgezeigt wird. Für c-orientierte ZnO-Dünnfilme wird das Wachstum im Detail untersucht und ein alternativer Abscheideprozess im so genannten Intervall PLD-Verfahren vorgestellt.
Die Verifizierung der theoretischen Prognose einer ferromagnetischen Ordnung mit einer Curie-Temperatur oberhalb Raumtemperatur (RT) für kubische, Mangan stabilisierte Zirkondioxid (MnSZ)-Dünnfilme stellt den dritten Teil der Arbeit dar. Die strukturellen Eigenschaften der Dünnfilme werden mittels XRD, AFM sowie Transmissionselektronenmikroskopie (TEM) untersucht. Die Bedingungen einer erfolgreichen Stabilisierung der kubischen Kristallphase durch den Einbau von Mn wird aufgezeigt. Mittels Röntgenphotoelektronenspektroskopie (XPS) sowie Elektronenspinresonanz (EPR) wird der Ladungszustand der, in der Zirkondioxidmatrix eingebauten, Mn-Ionen ermittelt. Die elektrischen Eigenschaftenwerden durch Strom-Spannungsmessungen(IU) sowie der Leitungstyp durch Seebeck-Effekt Messungen charakterisiert. Zur Erhöhung der Leitfähigkeit werden die MnSZ Dünnfilme in verschiedenen Atmosphären thermisch behandelt und Veränderungen durch IU-Messungen aufgezeigt. Ergebnisse von optischen Untersuchungen mittels Transmissionsmessungen und KL werden
präsentiert. Superconducting quantum interference device (SQUID)-Magnetometrie wird zur
Charakterisierung der magnetischen Eigenschaften genutzt. Magnetische Ordnungen im Bereich zwischen 5 K ≤ T ≤ 300 K werden untersucht und der Einfluss von Defekten sowie einer thermischen Behandlung in verschiedenen Atmosphären auf die magnetischen Eigenschaften diskutiert.
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Haas, Helge. "Effet Stark quantique dans les puits de CdTe/CdZnTe et développement d'un dispositif photoréfractif." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10146.
Full textAbstract:
Nous presentons le developpement et l'etude d'un dispositif photorefractif a puits quantiques ainsi que les mecanismes physiques fondamentaux associes a ce type de composants. La structure de bande de type i pour les trous lourds et de type ii pour les trous legers permet une mesure precise du decalage de bande de valence de cdte/cd#. #7#2zn#0#. #3#8te egal a +11% 2%. Cette situation particuliere produit une degenerescence entre niveaux de trous lourds et trous legers. Dans les puits peu profonds, l'exciton leger est de type i grace au potentiel coulombien exerce par l'electron sur le trou leger. Sous champ electrique, nous mettons en evidence une transition type i-type ii de l'exciton leger. Lorsque l'energie de liaison de l'exciton augmente, la constante dielectrique et l'interaction des excitons avec le reseau diminuent. L'observation de complexes exciton-phonon a basse temperature et leur disparition progressive lorsque l'energie de liaison augmente est favorable a cette interpretation. Une absorption excitonique intense a temperature ambiante est cependant observee lorsque l'energie de liaison est proche ou superieure a l'energie des phonons optiques longitudinaux. En nous fondant sur ces resultats, nous avons developpe un dispositif photorefractif a partir d'une diode schottky et nous avons mesure un rendement de diffraction proche de la valeur theorique. Un maintien du reseau de diffraction inscrit de quelques microsecondes necessite un blocage des porteurs qui ecrantent localement le champ applique. L'introduction de barrieres de potentiel en cdmgznte bloquent efficacement le mouvement perpendiculaire des electrons. Un modele qualitatif et des simulations numeriques permettent de cerner le comportement dynamique du dispositif. La diffusion laterale a l'interface est acceleree par le gradient de potentiel entre zones eclairees et sombres et limite le temps de maintien du reseau. Par des mesures de type pompe-sonde, nous avons determine la diffusion laterale et sa dependance avec le champ applique
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Gourgon, Cécile. "Fabrication et caractérisation optique de fils et boites quantiques CdTe/CdZnTe." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10145.
Full textAbstract:
Un certain nombre de techniques ont ete developpees ces dernieres annees pour fabriquer des nanostructures quantiques, principalement dans le domaine des semiconducteurs iii-v. Nous avons realise des fils et des boites quantiques de semiconducteurs ii-vi, a partir de puits quantiques cdte/cdznte, soit par nanolithographie et gravure de structures 2d, soit directement par epitaxie par jets moleculaires avec une croissance en deux etapes. Les proprietes optiques de ces nanostructures ont ete etudiees en photoluminescence a basse temperature (2k). Dans la premiere approche, les nanostructures ont ete obtenues par lithographie electronique et gravure seche. Nous avons developpe une etape de gravure supplementaire consistant en une oxydation anodique de la couche de surface. Cette etape permet de reduire la taille des fils et des boites et d'eliminer la couche de defauts introduite en surface par la premiere gravure. Les etudes optiques ont prouve l'existence de cette couche de defauts d'une epaisseur de 30 nm environ. Elle contient des centres radiatifs qui localisent les excitons et permet d'augmenter le rendement radiatif des structures de largeur superieure a 150 nm. Pour des tailles inferieures, les recombinaisons sur les defauts non radiatifs de surface font chuter l'intensite de luminescence. Pour s'affranchir des problemes dus a la gravure (fluctuations de largeur, defauts non radiatifs), nous avons developpe une autre approche basee sur une croissance epitaxiale directe. Un puits quantique cdte/cdznte est depose sur la face clivee 110 d'un superreseau contraint. Celui-ci induit une modulation de contrainte dans le plan de la recroissance, et donc un confinement lateral dans le puits 110. La luminescence de ces fils quantiques est decalee vers le rouge par rapport a celle du puits 2d. Ce decalage depend de la densite d'excitation, ce qui est explique par le champ piezoelectrique lateral dans les fils
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André, Régis. "Effet piézo-électrique dans les puits quantiques CdTe/CdMnTe et CdTe/CdZnTe." Université Joseph Fourier (Grenoble), 1994. https://tel.archives-ouvertes.fr/tel-00002688.
Full textAbstract:
Les materiaux de structure cubique blende de zinc sont piezo-electriques: une deformation de ces cristaux selon un axe polaire induit une polarisation electrique. Les puits quantiques contraints, de semi-conducteurs cubiques ii-vi ou iii-v, d'orientation 111 ou 211 presentent un champ electrique permanent de l'ordre de 100 kv/a pour 1% de deformation. Ces structures sont particulierement interessantes pour la modulation optique, mais il est necessaire d'etudier prealablement leurs proprietes specifiques avant de pouvoir envisager de les utiliser dans des dispositifs optiques. Dans ce but, nous avons etudie par spectroscopie optique des puits contraints cdte/cdmnte ou cdte/cdznte, elabores par epitaxie par jets moleculaires, avec comme axe de croissance 111 ou 211. Les resultats de spectroscopie ont ete confrontes a une modelisation en termes de fonctions enveloppes prenant en compte les effets de contraintes biaxiales pour une direction de croissance hhk. De plus, nous avons developpe une methode originale de mesure du champ piezo-electrique dans les puits quantiques grace a laquelle nous avons mis en evidence un effet piezo-electrique fortement non lineaire dans cdte. Cet effet n'avait jamais ete mentionne par ailleurs. Nous avons egalement mesure l'evolution du coefficient piezo-electrique e#1#4 cdte avec une forte pression hydrostatique, jusqu'a des deformations d'environ 2% et montre qu'une part des non-linearites provient d'un effet de volume. Enfin, nous avons etudie l'effet du champ piezo-electrique sur l'exciton. L'energie de liaison de l'exciton est assez peu affectee, par contre, force d'oscillateur decroit fortement pour la transition fondamentale du puits, avec le recouvrement des fonctions enveloppe d'electron et de trou. Notre modelisation de l'exciton, utilisant deux parametres variationnels, fournit un calcul precis, sans parametre ajustable, de l'absorption excitonique a travers un puits piezo-electrique: les calculs sont en tres bon accord, sur pres de deux ordres de grandeurs, avec les mesures d'absorption que nous avons realisees sur une serie d'echantillons de compositions variees
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Kheng, Kuntheak. "L'exciton chargé négativement X- dans les puits quantiques CdTe/CdZnTe." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10006.
Full textAbstract:
Nous presentons la premiere identification de l'exciton charge negativement x#- dans une heterostructure semi-conductrice, a savoir dans des puits quantiques cdte/cdznte. Nous avons etudie les caracteristiques de la transition optique x#- dans ces puits, notamment en presence d'un champ magnetique. La transition x#- est identifiee dans les spectres d'absorption de puits dopes par modulation avec des donneurs indium. Cette identification est basee sur l'augmentation de l'intensite de la raie x#- avec la concentration d'electrons dans le puits et sur les proprietes de polarisation circulaire de cette raie. Nous avons notamment verifie, par une analyse du taux de polarisation en fonction de la temperature, que le facteur g de l'etat initial de l'absorption x#- est bien celui de l'electron. En placant les plans d'indium dans differentes positions, dans les barrieres et dans les puits, nous avons etudie l'evolution de la raie x#- vers celle de l'exciton piege sur un donneur, d#ox. La force d'oscillateur de x#- est d'environ 10 fois superieure a celle de d#ox. La raie d'absorption x#- est observee pour toute valeur du champ magnetique dans les spectres des echantillons faiblement dopes et l'evolution de sa position en fonction du champ montre que l'espece x#- est probablement localisee par des fluctuations de potentiel dans le plan du puits. En revanche, les spectres de puits contenant un gaz d'electrons concentre (10#1#1cm#-#2) presentent a champ nul un pic associe a l'exciton de mahan et a champ faible des transitions entre niveaux de landau. A champ magnetique suffisamment intense les raies excitoniques x et x#- reapparaissent. Nous attribuons ce phenomene a une reduction des effets d'exclusion et d'ecrantage due au gel des electrons dans les fluctuations de potentiel. Le champ critique de reapparition des raies excitoniques peut servir a definir le seuil du changement de phase metal-isolant detecte optiquement
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Yang, Tsung-Han, and 楊宗翰. "Well-width dependent optical properties in m-plane ZnO/MgZnO quantum wells." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/7vbd5q.
Full textAbstract:
碩士國立交通大學
光電工程研究所
104
We report in this thesis experimental study on optical properties of nonpolar ZnO/MgZnO multiple quantum wells (MQWs) on m-sapphire with different well widths grown by pulsed laser deposition. The nonpolar ZnO/Mg0.1Zn0.9O was fabricated on Mg0.1Zn0.9O buffer by two-step growth, which effectively reduces the extra domain and surface roughness. Use 10% MZO as barrier and two temperatures to fabrication well and barrier, we can obtain narrower FWHM of well emission. On investigating the optical properties of different well-width MQWs by photoluminescence, we found the emission of near-band edge and basal-plane stacking faults are blue-shifted as decreasing the well width. The result of exciton and LO-phonon coupling and exciton binding energy for each sample reveal that the quantum confinement effect plays a dominant role. Additionally, we use several analyses to prove that there is absence of the quantum confined Stark effect in our samples. We also discuss the optical anisotropy properties of our nonpolar MQWs. Finally, through observing many optical behaviors for the thickest well width sample which does not follow the same trend as the others, we understand the influence of extra (101 ̅3) domain in well width 11 nm MQWs.
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Chang, Jen-Hao, and 張仁豪. "A Study on the Characteristics of AlN-ZnO/ZnO/AlN-ZnO Double Heterojunction and Quantum Wells Structure." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/7x6796.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
102
In this study, the use of RF magnetron sputtering system, namely the use of zinc oxide, aluminum nitride target, AlN-ZnO cosputtered films as a barrier layer and an undoped ZnO film as a active layer to production double heterojunction and quantum well structure. Measurement optical and electrical properties of the structure, Optical characteristic, PL characteristic and crystallize,by changing the thickness of the different active layer .The results,AlN-ZnO/ZnO/AlN-ZnO double heterojunction and quantum well structure after vacuum annealing, the average penetration can be more than 80%. The AlN-ZnO/ZnO interface of the diffusion of aluminum atoms substituted with a zinc atom, the electron carrier to provide more,therefore, compared with the non-doped zinc oxide, double heterostructures and quantum well structure electron carrier concentration has improved significantly. With the well thickness reduction,the barrier layer of aluminum atoms diffuse the situation more obvious,thus the radiative recombination centers gradually weakened and towards long-wavelength red shift. Further short-wavelength photoluminescence spectrum fitting analysis can be found when the well region thickness is reduced from 50 nm to 7 nm, the peak fitting band edge radiation in the blue-shift of about 35 meV, mainly because with the well layer thickness decreases, the quantum confinement effect will be more obvious, therefore, to produce a blue shift and blue shift size similar results with the theoretical values calculated. Then,the AlN-ZnO barrier layer and undoped ZnO well layer are repeatedly stacked to form multiple quantum well structure. It can be found, the multilayer structure can provide more potential wells, so that more electrons and holes are confined potential well zones, increasing the number of electrons and holes complex, leading to radiative recombination radiation peak intensity with quantum wells periods to increase of phenomena which have significantly enhanced. The radiative recombination radiation peak positions with increasing of quantum wells periods have blue shift and then redshift phenomenon, mainly because with increasing of quantum wells periods, quantum effects are more apparent when the periods of quantum wells increase to ten periods, due to excessive film stack, resulting in a large accumulation of stress in the structure, resulting in crystallization characteristics deteriorate, resulting redshift.
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Chang, Ning-An, and 張寧安. "In-plane anisotropy in m-plane Zn0.8Mg0.2O/ZnO multiple quantum wells." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/10625910384691931363.
Full textAbstract:
碩士國立交通大學
光電工程研究所
103
This thesis report the experimental study of nonpolar ZnO/Zn1-xMgxO multiple quantum wells (MQWs) on m-plane sapphire by pulsed laser deposition. The nonpolar x = 0.2 MQWs were fabricated on the 10% m-MZO buffer by two-step growth, which effectively reduces the extra domain and surface roughness but produces high basal-plane stacking faults (BSF) density. The photoluminescence (PL) spectra show a blueshift near-band edge (NBE) emission and strong stacking faults, coming from both substrate and heterostructure, optical emissions of MQWs. We also investigated the exciton – LO phonon coupling and the exction binding energy for each sample and compared that with the previous x = 0.1 MQWs results of our group. The results indicate the quantum confinement effect play a dominant role. Additionally, we used various analyses to identify that there have no internal electric in our samples. Finally, we discuss the optical anisotropy properties of our non-polar m-plane MQWs with x = 0.2.
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Ting, Shao-Ying, and 丁紹瀅. "Growth, Characterization, and Light-emitting Diode Application of CdZnO/ZnO Quantum Wells." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/60285232826309146319.
Full textAbstract:
博士國立臺灣大學
光電工程學研究所
100
In this dissertation, we first demonstrate the growths of CdZnO/ZnO quantum well (QW) samples on GaN and ZnO templates under different growth conditions with the plasma-assisted molecular beam epitaxy (PA-MBE). Temperature-dependent and excitation-power-dependent photoluminescence (PL) measurements are undertaken for illustrating their different emission characteristics. The crystal characteristics of the QWs structures are measured by high-resolution transmission electron (TEM), X-ray diffraction (XRD). It is found that the Cd incorporation on the ZnO template is lower, when compared with that on the GaN template, such that the O2 flow rate needs to be reduced for stoichiometric CdZnO/ZnO QW growth on the ZnO template. Besides the wurtzite (wt) CdZnO structure, the rock-salt (rs) CdZnO structure exists in the CdZnO well layers when the total Cd content is high. The rs structures may dominate over the wt structures in PL intensity when the total Cd content is high. In either group of samples on the GaN and ZnO templates, the emission efficiency first increases and then decreases with increasing total Cd content. The low emission efficiencies at low (high) Cd contents are attributed to the weaker quantum confinement (poorer crystal quality) of the QWs. The emission efficiencies of the QW samples on the GaN template are generally higher than those on the ZnO template. The strength of the quantum-confined Stark effect generally increases with increasing Cd content in either group of samples on the GaN and ZnO templates. Besides, a CdZnO/n-ZnO multiple-QW lateral light-emitting diode (LED) grown with the QWs and n+-ZnO capping layer with MBE on p-GaN, which is grown with metalorganic chemical vapor deposition (MOCVD), is fabricated and characterized. On the epitaxial surface, there exist some V-shape pits, which correspond to threading dislocations beneath. With SiO2 nanoparticles filling in the pits, the turn-on voltage and device resistance of this device are around 4 V and 224 Ω, respectively. However, because of the weak carrier localization mechanism in the ZnO-based LED, its defect emission is quite strong and dominates the LED output at low injection current levels. The blue shift of LED output spectrum in applying a forward-biased voltage and the large blue-shift range in increasing injection current show the different behaviors of such a ZnO-based LED from those of a nitride LED. In addition, we also demonstrate the fabrication procedures and characterization results of a vertical light-emitting diode (VLED) with the CdZnO/n-ZnO QWs and n+-ZnO capping layer grown with MBE and the p-GaN layer grown with MOCVD. Its performances are compared with those of a lateral LED based on the same epitaxial structure to show the significantly lower device resistance, larger spectral blue-shift range in increasing injection current, smaller leakage current, weaker output intensity saturation, and relatively lower defect emission in the VLED.
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Wang, Hsuan-Min, and 王宣民. "Photoluminescence Properties of ZnO/MgZnO Single Quantum Wells on C-Plane Sapphire." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/25526427426364211942.
Full textAbstract:
碩士國立交通大學
顯示科技研究所
101
We have successfully grown three thicknesses of single quantum wells (SQWs) by pulsed laser deposition (PLD), which are 2nm, 4nm, and 5.2nm,respectively. Using temperature and pumping power dependent photoluminescence (PL) spectroscopy, we analyze these SQW samples and discuss the properties of (1) phonon interaction, (2) exciton binding energy, and (3) built-in electric field on these samples. From the low-temperature PL spectra of the SQWs have blue shifted D0X emission for 2 nm with the exciton binding energy large than 60meV, whereas, the exciton binding energies for 4nm and 5.2nm SQWs are 54 and 48 meV, respectively, which are less than 60 meV of the bulk ZnO and the phonon interaction decreases with decreasing well width. These results reveal the SQWs possess not only quantum confinement effect but also quantum confined Stark effect with built-in electric field. Furthermore, there is an apparent extra spectral peak in the PL spectrum of the 5.2nm SQW at 3.34eV about 45 meV below the exciton emission. In order to explore the origin of this peak, we made excitation density dependent PL measured at 80K. The results reveal that this extra peak shifts from 45 meV below the exciton emission to about 30 meV at high excitation density. We therefore attribute this peak to the exciton-exciton scattering or so-called the P-band emission that shows changing from P(infinity) emission (45 meV below exciton emission) at low excitation to P2 emission about 30 meV below exciton emission at high excitation density.
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Chen, Guan-Rong, and 陳冠融. "Polarization Characteristics of Stimulated Emissions from c-plane ZnO/ZnMgO Multiple Quantum Wells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ze6ccn.
Full textAbstract:
碩士國立臺北科技大學
光電工程系
106
In this work, we investigated the polarization properties of stimulated emission (SE) from ten-period ZnO/ZnMgO multiple quantum wells (MQWs) on a c-plane sapphire substrate, which was produced by the pulsed laser deposition technology. Through the excitation of 266 nm Q-switched laser with 10 Hz repletion rate, the SE can be excited owing to the exciton-exciton scattering (ex-ex scattering). The thickness of well and barrier of MQWs were about 2.5 nm and 13.1 nm, respectively. First, the edge emission measurement was carried out using a cylindrical lens to focus the pump beam onto the MQWs with a long line stripe. By rotating a linear polarization, the spectrum component of SE was measured to demonstrate that linear polarized light, with the degree of polarization about 0.95. In addition, the electric field of emission light was perpendicular to the c-axis of MQWs and the photon energy of SE was fixed at around 3.287 eV. At lower excitation energy, the spontaneous emission of MQWs was un-polarization and revealed the shift of photon energy about 35 meV from A-band to C-band. Using a cylindrical lens as a pump lens, a linear polarized emission light, with the degree of polarization about 0.85, was also revealed from normal emission of MQWs. Owing the waveguide effect, the polarization of the SE is perpendicular to the long line stripe of pump beam but independent on the pump polarization. In order to investigate the influence of waveguide effect, a plano-convex lens was used to replace the cylindrical lens and lower the polarization characteristic of SE with the degree of polarization about 0.42. Because of the relatively poor beam quality of the low repletion rate Q-switched laser, the waveguide effect can still exist to produce the polarized SE from MQWs through a plano-convex lens.
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Wu, Yu-Fan, and 吳雨帆. "Photoluminescence study of coupling in c-plane ZnO/Zn0.88Mg0.12O asymmetric double quantum wells." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/42566150972697866612.
Full textAbstract:
碩士國立交通大學
光電工程研究所
104
Asymmetric double quantum well (ADQW) structure is consisted of two quantum wells with different well widths. While the width of barrier between two wells reduce specifically, coupling effect will take place and make carriers probable tunneling from the narrow well to the wide well. We have fabricated ZnO/Zn0.88Mg0.12O ADQW on c-plane sapphire substrate by pulsed laser deposition, photoluminescence (PL) measurement results compared with finite difference simulation are used to investigate the coupling in the ADQW. In our research, we observe that the PL intensity ratio of wide well to narrow one apparently increase under coupling. On the other hand, coupling effect makes carriers in different wells probable recombining, the corresponding exciton transition energy increase since the spatial separation of electrons and holes wave function resulting in reduction of exciton binding energy. While barrier and well width reduce at the same time, the PL emission intensities and full widths at half maximum (FWHM) of wide and narrow wells in the coupled ADQW are significantly different compared to the uncoupled ADQW. Through comparing the experimental and simulate results, we attribute both the FWHM of wide wells increasing and the PL emission intensities of the narrow wells decreasing to the carriers tunnel from narrow well to wide well. In addition, the swap of the narrow and wide well exciton binding energy between coupled and uncoupled ADQW can be deemed to the evidence of coupling between two wells with thin barrier and carriers tunneling from narrow well to wide well is indeed.
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Shih, Han-Yu. "Studies and Applications of Optical Properties in Semiconductor Nanostructures: InGaN/GaN multiple quantum wells and ZnO nanorods." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2207200814121700.
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Shih, Han-Yu, and 施函宇. "Studies and Applications of Optical Properties in Semiconductor Nanostructures: InGaN/GaN multiple quantum wells and ZnO nanorods." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/29910132514863910052.
Full textAbstract:
碩士國立臺灣大學
物理研究所
96
Nanotechnology gives people a great future and conveniences. Semiconductor materials are widely made into nanostructures, and they show rather different electrical, magnetic, and optical properties from bulk materials. In this thesis, we investigated two semiconductor nanostructures, InGaN/GaN multiple quantum wells (MQWs) and ZnO nanorods, and found some novel phenomena. There usually exists a good piezoelectric effect in nitride wurtzite structure, such that InGaN/GaN MQWs have obvious build-in electric field in them, and this property could be used to construct a biosensor. As the hybridization process of deoxyribonucleic acid (DNA) occurs on InGaN/GaN MQWs, the electric field in MQWs would be altered by the polarity of DNA molecules, and the photoluminescence (PL) spectra, Raman spectra, and the calculated strain of InGaN lattice could also be changed due to the quantum confined Stark effect. As a result, InGaN/GaN MQWs have a great opportunity in the development of DNA-sequence identification. On the other hand, our group had found a phenomenon called photoelastic effect in ZnO nanorods last year, and we further expected that the thinner nanorods, the mightier photoelastic effect exists in them. In this thesis, three diameters of thick, mid-thick, and thin ZnO nanorods are studied. It was observed that the PL spectra, Raman spectra, and the calculated strain would be changed with different excitation Laser power. Besides, the amounts of change are greater in thinner nanorods. This result gives a good evidence to proof our expectation, and provides much novel information to optoelectric device developers.
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Huang, Wei-Lun, and 黃偉綸. "Structural and Optical Properties of ZnO/MgxZn1-xO Multiple Quantum Wells Using a Y2O3 Buffer Layer on Si (111)." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/68410280135324073908.
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碩士國立交通大學
工學院加速器光源科技與應用碩士學位學程
104
This thesis reports the growth and physical properties of ten-period ZnO/MgxZn1-xO multiple quantum wells (MQWs) prepared on the most widely used semiconductor material, Si. The introduction of a nm-thick Y2O3 transition layer between Si (111) substrate and a ZnO buffer layer significantly improves the structural perfection of the MQWs grown on top of it. Single phase MgxZn1-xO with Mg contents x approximately higher than 0.33, as determined from its lattice constants and cathodoluminescence emitted peak position, was adopted as the barrier material. The high structural quality of the ZnO/MgxZn1-xO MQWs is evidenced by the appearance of pronounced high order satellite peaks in X-ray crystal truncation rods; high resolution cross-sectional TEM images also confirmed the regularly arranged well and barrier layers. We studied the dependence of the near-band edge (NBE) emission transition in ZnO/MgxZn1-xO MQWs on well layer thickness in details. The dominated PL peak of the MQWs shows a significant blue shift with decreasing well width, which is consistent with the quantum confinement effect. From the power-dependent PL spectra conducted at 10k, we observed that built-in electric field effect in MQWs can be negligible when the well width is less than ZnO excition Bohr radius (~3 nm). Moreover, the temperature dependence of PL spectra is investigated to reveal the localization, relaxation and recombination mechanisms of the photo-generated carriers. Our results indicate that ZnO/MgxZn1-xO MQWs integrated on Si have great potential in UV optoelectronic device applications.
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Chun-Yung, Chi. "Transmission Electron Microscopy Studies on InGaN/GaN Multiple Quantum Wells with H2 Process in Barrier Layers and ZnO Thin Films on GaN with Different Growth Temperatures." 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0907200514201500.
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Chi, Chun-Yung, and 紀淳詠. "Transmission Electron Microscopy Studies on InGaN/GaN Multiple Quantum Wells with H2 Process in Barrier Layers and ZnO Thin Films on GaN with Different Growth Temperatures." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/54189355295544569620.
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碩士國立臺灣大學
光電工程學研究所
93
In this research, we perform the optical and material analyzes of five InGaN/GaN multiple quantum wells of different H2 process conditions in growing barriers. Also, ZnO thin film structures on GaN grown at different temperatures are studied. The material analysis methods include high-resolution X-ray diffraction (HRXRD), high-resolution transmission electron microscopy (HRTEM), and strain state analysis (SSA) In optical characterization the fundamental optical properties are obtained with photoluminescence spectroscopy. We study the effect of H2 process in barriers of InGaN/GaN quantum well structures. In the PL results, we find that aggregation structures exist in the sample without H2 process. Also, the PL spectral peak vary over the wafer. In TEM results, we find that H2 process lead to stronger indium confinement in the well layers and can suppress the spinodal decomposition in the rim part of the wafer. By analyzing TEM images with SSA, we find that strong strains exist in the sample with H2 process such that spinodal decomposition become weaker. Besides, in 3D SSA images, we can see that the central part of the wafer have a better-defined quantum-well structure than that in the rim part. In XRD results, we find that the signal of quantum-well structures is quite strong in the central part of the wafer. Also, with the H2 process, the average content of indium in the sample is decreased. Then, we compare the nano-structures of three samples of ZnO thin films grown on GaN with different growth temperature conditions. Although disconnected spiral domain structures (at the order of 100 nm in width) were observed in the samples of high-temperature growth, the crystal quality is generally better than the one grown at the low temperature, either near the sapphire interface or far away from the interface. In the sample of high temperature growth through the whole process, the domain structures extend from the interface with a smaller scale and almost vertical sharp boundaries. The sample grown at the low temperature showed a connected structure from the interface. However, its crystal quality is quite poor. In the sample with initial low temperature growth and then high temperature growth, the ZnO layer started with a connected structure, like the sample of low temperature growth. However, it evolved into domain structures like the sample of high temperature growth beyond about 200 nm in thickness. The samples of high-temperature growth generally have higher photon emission efficiencies. The sample grown at the high temperature through the whole growth process has the highest quantum efficiency.
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Chiu, Hung-Jen, and 邱黌壬. "Investigating Characteristics of AlN-ZnO/ZnO/AlN-ZnO Structure Applied to Multi-Quantum Well." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/3wks3w.
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碩士國立虎尾科技大學
光電與材料科技研究所
103
In this study, by using RF magnetron co-sputtering system with ZnO and AlN target, respectively, deposited un-doped ZnO thin films and ZnO doped Al thin film, and using AlN-ZnO sputtering thin film to be a barrier layer, un-doped ZnO thin films to be active layers to produce double heterostructures and multi-quantum well structure, second annealing under vacuum ambient activates the dopant atoms in the films. After annealing under vacuum ambient, We measured our samples about the electrical properties, optical properties of thin films with photoluminescence light-emitting properties and the composition with the film crystal structure and analysis the thin film carrier mechanism and conduction type. Result of the study, after annealing under vacuum ambient, observed the average transmittance were over 80% about the double heterostructure (AlN-ZnO/ZnO/AlN-ZnO) and multi quantum well structure, due to the interface of AlN-ZnO / ZnO diffusion of aluminum atoms substituted the zinc atom, to support more electronic carrier, therefore, comparing with the un-doped ZnO, the electron carrier concentration has improved significantly of the double heterostructure and Multi-Quantum Well structure. Next, the barrier layer(AlN-ZnO) and un-doped well layer(ZnO) repeat stacked to form a multi-quantum well structure, observed the multilayer structure can provide more potential energy well, so the more electrons and holes are confined to potential energy wells layer, leading to the peak intensity increases of the radiative recombination radiation with increasing the number of quantum wells and has significantly enhanced the phenomenon, when quantum well layer increased to thirty period, due to quantum well stacked a lots, the number of electron and hole composite reach a saturation, due to the structure with multilayer stack makes a lot of accumulated stress, caused by the crystallization characteristics worse, Which led to a multi-quantum well structure luminous intensity rise less obvious, even the multiple-quantum well’s period were more than 25-period, the luminous intensity will gradually shows the trend of a level of saturation trend.
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jiang, jhong-ying, and 江忠穎. "The study of p-NiO/MgZnO-ZnO quantum well/n-ZnO photodetectors." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3wn4jh.
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碩士國立嘉義大學
電子物理學系光電暨固態電子研究所
106
In this thesis, the p-i-n diodes were fabricated by depositing p-NiO/MgZnO-ZnO quantum well (QW)/n-ZnO structure on ITO/glass substrate using magnetron sputtering system. First, the n-ZnO was deposited on ITO/glass substrate, then the MgZnO/ZnO QW was grown on ZnO surface with various MgZnO barrier layer thickness (10, 25, 40, and 60 nm) and ZnO well thickness of 4 nm. Next, p-NiO and electrodes were coated to fabricate the p-i-n diodes. Effects of various barrier layer thickness on the diodes were studied. The p-n diodes without QW structure (i.e., p-NiO/n-ZnO) exhibited rectifier characteristic, but the rectifier characteristic was improved after adding MgZnO/ZnO QW. As compared with the diodes without QW, the rectification ratio was greatly enhanced from 14.9 to 95.7 at ±2.5 V bias-voltage. As for photoresponse, both the visible- and ultraviolet-photoresponse decreased with barrier layer thickness. The largest 280/500 nm rejection ratio was observed in the p-i-n diodes with QW structure. The 280/500 nm rejection ratio was enhanced from 159 for the diodes without QW to 3030 for the diodes with QW and 25-nm barrier layer thickness by a magnitude of 19 at 1-V reverse-bias voltage, indicating the diodes with QW and 25-nm barrier layer thickness presented the largest noise-rejection ability.
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Tsai, Bor-Sheng, and 蔡博升. "Investigation on AlN-ZnO/ZnO Quantum Well Structure and Fabrication on Light-Emitting Diode." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4p3q3w.
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碩士國立虎尾科技大學
光電與材料科技研究所
103
The study by RF magnetron co-sputtering system, aluminum nitride - zinc oxide target to produce a non-doped zinc oxide and aluminum nitride film - co-sputtered film of zinc oxide and zinc oxide to produce a heterostructure, aluminum nitride - zinc oxide and aluminum nitride double heterostructure - ZnO quantum well structure, for the double heterostructure and quantum well structures of different thickness of the active layer to Photo limuniscence measurement and Hall measurements investigate the structure of the optical and electrical properties, Hall measurements show the electrical characteristics of the film carrier concentration has decreased phenomenon, and Photo limuniscence measurements show since the aluminum atom diffusion effect, a double heterostructure and quantum well structures can suppress the ZnO defect - oxygen vacancy, from Electrical limuniscence measurement can be found that reduce the thickness of the active layer inside the device enables carrier confinement effect and composite efficiency, active layer thickness of 20 nm, the light-emitting wavelength of 420 nm and 610 nm, the light-emitting is tend to white emission(CIE1931 X = 0.3330 Y = 0.3138), when the active layer thickness decreased to 5 nm, emission wavelength becomes 408 nm, the light emitting is tend to blue-violet light emission(CIE1931 X = 0.2615 Y = 0.2370), the result show that reduce the thickness of the active layer can improve the carrier confinement effect and recombination efficiency, and in order to further enhance the element luminous efficacy, thus making a multiple quantum well structure elements from Electrical limuniscence measurement can be observed, as well area of increasing the number of carriers in the ZnO layer confinement effect and gradually increase recombination efficiency, so that the element luminous efficacy improved, the light intensity increased, blue shift of the emission peak generation phenomenon, when the well area to increase the number to 10 period, component emission peak moved sharply Blue 385 nm, very close to the oxidation the nature of the light-emitting ZnO, the light emitting is tend to violet light emission(CIE1931 X = 0.2703 Y = 0.1893). The result prove that increase the number of well region can enhance the effects and limitations of carrier recombination efficiency. Since the elements have thermal effects at high current operation, in order to reduce the thermal effects for components to influence and enhance the element luminous efficacy, so the carrier confining layer from 50 nm decrease to 20 nm and 10 nm, after calculated that the series resistance from 8.33 kΩ decrease to 6.6 kΩ, due to the series resistance is reduced, the thermal effects can be droop, the light emission performance can be improvement, the light emission intensity increased roughly 1.29 times.
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Chen, Po Ju, and 陳柏儒. "Study of material and optical characteristics of ZnO quantum well." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/57960680528537602333.
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碩士國立中正大學
光機電整合工程研究所
99
Epitaxial growth of ZnO thin films with MgO and GaN buffer layer were grown on (0001) c-sapphire by molecular beam epitaxy (MBE). The effect of GaN and MgO buffer layers prepared on optical, crystal and morphological properties of HT-ZnO layer is reported. The MgO and GaN buffer layer has shown the beneficial effect on crystal quality and morphological properties, as expressed by the narrowing of (002) diffraction peak (FWHM = 48.66 (MgO), 242.58 (GaN), 791.74 (ZnO without buffer layer) arcsec) and grain size enlargement. Threading dislocations of MgO buffer sample are not along the c axis so that they strongly interact with each other and annihilate quickly, but GaN buffer sample is not. The results show that the strain in ZnO with MgO and GaN buffer layer is compressive, which is also supported by X-ray diffraction (XRD) Measurement. This compressive can solve the cracking problem in the Epitaxial growth of ZnO thin films. The optimum AFM RMS is 2.875 nm with MgO buffer layer. The MgO buffer sample exhibits the highest edge band and deep level emission ratio and smallest concentration of oxygen vacancy by photoluminescence (PL) measurement. The improvement of optical characteristics is due to the better crystal quality of the buffer layer samples compared to that of the ZnO ample without buffer layer. The study suggests that by employing an appropriate buffer to modify the initial nucleation environment, high quality heteroepitaxy is achievable even with large misfit between sapphire and ZnO. In addition, ZnO/Zn1-xMgxO single and multiple quantum wells were grown on a c-sapphire substrate by molecular beam epitaxy using a MgO/ZnO buffer layer. The c-lattice parameter is dependent from Mg concentration, it decreases from 5.198 Å to 5.182 Å, corresponding to the Mg concentration is 0.1 and 0.2. The low temperature photoluminescence peak of the single quantum wells shifted from 3.369 to 3.393 eV as the Mg concentration was increased from 0.1 to 0.2, indicates an enhancement of the exciton binding energy in ZnO quantum well with decreasing Mg concentration. The temperature-induced shift at 10-300 K is caused by a change in the exciton dynamics with increasing temperature due to the exciton localization effect. ZnO/Zn0.8Mg0.2O has obvious S-shift phenomenon, while that in ZnO/Zn0.9Mg0.1O was similar to that in bulk ZnO. ZnO/Zn0.8Mg0.2O multiple quantum well structure because the uneven distribution of Mg concentration, leading to its PL emission wider. In order to reduce the surface roughness, optimal ZnMgO layer thickness is the key for high quality ZnO/ZnMgO multiple quantum well.
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Jia-Ling, Tian, and 田佳玲. "Optical properties of Zn1-XCdXSe/ZnSe multi-quantum wells." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/71437966880305576947.
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碩士淡江大學
物理學系
87
The main purpose of this study is to analyze the optical properties of Zn1-XCdXSe/ZnSe MQWs. We expect to improve the exciton''s lifetime, emission efficacy, and threshold current density of lasing by understanding the optical mechanisms of the material. It is well known that excitons play an important role in the radiation mechanisms of Ⅱ-Ⅵ semiconductor MQWs at low temperature. Therefore, at low temperature, the spontaneous emission is caused by exciton recombination. Furthermore, the stimulated emission mechanisms are dominated by biexciton, exciton-exciton scattering, exciton-electron scattering, EHP（electron-hole plasma） recombination. We establish correlation of all of above mechanisms in different pumping intensities. We have measured the spontaneous emission on samples with various temperatures and well widths. With increasing the temperature, the energy gap becomes narrow leads to a red shift of peak energy. The FWHM（full width at half maximum） is broader with increasing temperature because of the exciton-Lo-phonon coupling. The well width is broader, the exciton-Lo-phonon coupling is stronger. With increasing the well widths, due to quantum confinement effect, the spectrum shows a red shift of the peak energy. The FWHM for narrow well samples become broaden because the well thickness fluctuations. We also have measured the stimulated emission on samples with different excitation intensity at different temperatures. By increase the excitation intensity at 15K, the stimulated emission mechanisms are changes from B1, B2 band（biexciton）,to P band（exciton-exciton scattering）,E band（exciton-electron scattering）, and N band（EHP recombination）, respectively. When changing temperature from 15K into 100K and 200K, the situation of emission are similar. However, the threshold excitation intensity is higher and the radiative mechanisms with excitons are dissolving gradually, with increasing temperatures. The stimulated emission mechanisms elucidated in the present study are closely related to those taking places in ZnSe-based blue-green semiconductor lasers.
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Lin, Hong-Jyun, and 林泓均. "A Study of AlN-ZnO/ZnO Quantum Well Structure with barrier layer Applied to ZnO/GaN Light-Emitting Diode." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7zw8s2.
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碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
105
In this study, we use RF magnetron co-sputtering system to deposit the ZnO thin film and AlN-ZnO co-sputtered thin film by Aluminum nitride (AlN), Zinc Oxide (ZnO) target, and Fabrication the ZnO/GaN heterostructure and AlN-ZnO/ZnO quantum well structure. The influence of different barrier layers on the Zinc Oxide quantum well is also discussed. The upper barrier layer was fixed with AlN-ZnO (40%) thin film，the lower barrier layer was divided into AlN-ZnO(40%) and AlN, and define both as “Single Quantum Well” and “Asymmetry Single Quantum Well”. For the different barrier layer of ZnO quantum well structure, The photoelectric characteristics of ZnO quantum well structures are discussed by using PL measurement and Hall measurement system.It shows the carrier concentration of Single Quantum Well (SQW) increased due to the diffusion of Al atoms, The ZnO intrinsic defect–oxygen vacancy (Vo) can be suppressed and improved the ZnO crystallinity.The Asymmetry Single Quantum Well (A-SQW) is subjected to excessive diffusion of Al atoms in the lower barrier layer AlN, the oxygen vacancy of ZnO can be suppressed, but it produces too many insulated Al-O bonds, which leads to higher structural resistivity and lower carrier concentration, which leads to poor crystallinity of ZnO. From the EL measurements, we can find that the dominant wavelength of the SQW/p-GaN LED is located at 410 nm, the emission color is close to blue-violet. The A-SQW/p-GaN has weak luminescence intensity, but the AlN barrier layer provides better carrier confinement capability, which makes the p-GaN-related emission and interfacial recombination decreased, and the dominant wavelength is located at 390 nm. In order to improve the luminous efficiency of LED devices, and keep the crystallinity of ZnO. The different thickness of AlN barrier, 10, 20, and 35 nm are deposited on p-GaN substrates, and deposited the single quantum well structure. From the PL measurements and XRD spectra, it is observed that the three structures have the diffusion of Al atoms to influence the crystallinity of ZnO, However, the overall crystallinity is better than the asymmetric quantum well structure. From the EL measurements, it can be found that the luminescence component of p-GaN decreases gradually with increase the thickness of AlN barrier layer. When the thickness of AlN barrier layer is limited to 20 nm or more, the intrinsic luminescence of ZnO begins to appear, the dominant wavelength is gradually blue-shifted from 410 nm to 390 nm. In order to further enhance the single luminous efficiency of LED devices, AlN barrier layer 35 nm was deposited on p-GaN substrate. And further improve the quantum wells to 3, 5, 7, 10 periods. From the EL measurements, it is found that the overflow of the carriers is suppressed when the period of the quantum wells increases. There are more electron-holes that can produce effective radiation recombination in the well region, and the luminous intensity of the LED devices increases with the period of the quantum wells. The dominant wavelength of the LED is blue-shifted from 390 nm to 385 nm, indicating that the LED luminescence is dominated by ZnO intrinsic luminescence.
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Hsu, Kai-Chiang, and 許凱強. "A Study of the Improvement on AlN-ZnO/ZnO Quantum Well Structures Applied to Light-Emitting Diode." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/r4de82.
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碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
104
In this study, we use RF magnetron co-sputtering system to deposit undoped ZnO thin film and AlN-ZnO co-sputtered thin film by AlN, ZnO target, and make ZnO heterostructure, AlN-ZnO quantum well structure, and then by decreasing AlN-ZnO barrier layer thickness to improve the structural properties. For different barrier layer thickness of the quantum well structure, using Hall measurement system and photoluminescence measurement system to study the structure of the different barrier layer thickness photoelectric properties. The structure properties are displayed in the Hall measurement; it shows the concentration of quantum well structure increasing by decreasing barrier layer thickness. Photoluminescence measurement results due to the diffusion of Al atoms, so single quantum well structure ZnO intrinsic defect – oxygen vacancy can be suppressed. And then from the electroluminescence measurement result, it shows by decreasing barrier layer thickness can reduce the device series resistance, thereby reducing the impact of the thermal radiation effects, thus the intensity of electroluminescence can be enhancing, the emission peak of electroluminescence located at 410 nm, the device light emitting is showed blue-violet. When the barrier layer thickness decrease to 20 nm, the emission of electroluminescence produced peak 610 nm, the short wavelength red-shift, the device light-emitting is showed orange, and the wide band emission at 610 nm emerging from the Ga-O interlayer. Thus when the barrier layer thickness is 35 nm, the structure can be effectively enhanced the intensity of short-wavelengths, and the Ga-O interlayer also be suppressed. To further enhance the light emitting diode emitting performance, in optimal conditions to make different period with different barrier layer thickness quantum well structure, there are 1, 5, 7 and 10 period multiple-quantum well structure light emitting diode. From the electroluminescence measurement result, it shows the same period with decreasing barrier layer thickness device can reduce the series resistance, and the intensity of short wavelength enhance slightly. With increase in the number of the period, the carrier confinement effect and the carrier recombination efficiency are rose, it can enhance the device emitting performance. By decreasing barrier layer thickness the thermal radiation effects also be reduced, and thereby enhancing the device intensity of short wavelength. The emission peak of electroluminescence blue-shift after increasing the number of the period. From 1 period to 10 period multiple-quantum well structure, the emission peak was blue-shift from 410 nm to 385 nm, the device emitting from original blue-violet light turned to purple light, it close to intrinsic emitting of ZnO. Thus when the number of the well period increase, the intensity of short wavelength enhances obviously, and by decreasing barrier layer thickness can reduce the device series resistance, the intensity of short wavelength can be further enhanced.
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Ton, Ho-Jei, and 童厚傑. "Transient absorption spectroscopy of ZnO/ZnMgO quantum well by pump probe technique." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/546ww3.
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碩士國立臺北科技大學
光電工程系研究所
98
We have investigated the ultrafast carrier dynamics of ZnO/ZnMgO quantum wells by the time resolved measurement using the femtoscond Ti:sapphire oscillator from above band gap to band tail (358-385 nm). As the photo-excited energy above the band gap of the ZnO, the effect of the band filling (BF) and band gap renormalization (BGR) will occur sequentially and compete to each other. As excited photon energy within below band-gap and near exciton resonance, only positive transmission change can be seen that is due to band filling. The maximum transmission change will occur at the free exciton resonance and reveal the saturation behavior at higher exited intensity. In our estimation, exciton binding energy about 76 meV is obtained by the difference between the band gap and exciton resonance that is larger than the ZnO due to quantum confinement effect. In comparing with the ZnO thin films, the exciton dynamics of MQW have a longer radiation time (200ps) that can be explained by quantum confined stark effect (QCSE) by internal field in the hetero-structure. When we increase pumping density near exciton state, screening of QCSE will result in reduction of spontaneous emission lifetime. At shallow band tail states, both BF and BGR effects will exist after excitation of carriers that is similar to that at far above band gap. In our measurement, the two-photon absorption (TPA) is observed and the maximum value is located at excited state of 376 nm. Deep band tail has weak absorption and slow decay might due to phonon-assisted transferring to deeper states.
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Lin, ChienLiang, and 林建良. "Studies on the Optical Properties of Zn1-xCdxSe/ZnSe Semiconductor Quantum Wells." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/80017969133102230944.
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碩士國立交通大學
電子物理系
87
In this work, we use the Photoluminescence (PL), Reflection, Raman spectroscopy measurement and transmission electron microscopy (TEM) to study the optical properties of Zn1-xCdxSe/ZnSe semiconductor quantum wells that were grown by Molecular Beam Epitaxial (MBE) system. Experiments have three parts： I. We use the finite quantum well model to imitate the Zn1-xCdxSe/ZnSe quantum well structure. Then, we calculate the quantum well confinement energies in the valence band and conduction band. We also introduce the excitonic binding energies in the calculation. Thus, we get the emission energies of the quantum well. These results are compared with the PL spectra and then we can determine composition parameters x of the quantum wells. II. The emission energies of the Zn1-xCdxSe/ZnSe QWs at room temperature are not high enough to obtain higher luminescence. Therefore, we introduce the ZnMgSSe as the cladding layer and use its smaller refractive index than ZnSe to confine optical field within the active region (QWs). We also increase the layers of quantum well to enhance the emissive intensity. The experimental results prove that this way is effective. III. When we used the ZnMgSSe guide layer to enhance emissive intensity, deoxidized GaAs surfaces were attacked by sulfur atoms. Therefore, we introduce the strain layer superlattice buffers, ZnSe/ZnSSe, and buffer layers, ZnSe、GaAs, to suppress the generation of defects. The results show that the buffer layers enhance the efficiency and of quality emission successfully, and also reduce the PL peak full width at half maximum (FHWM) effectively. IV. In order to ascertain the thin films of each layer crystalline quality and their compositions, we use the Raman spectroscopy measurement. We measure the phonon vibration energies of each layer. These phonon vibration energies are peculiar to thin films, and they do not vary with the temperature. Thus, we can use Raman spectra to ascertain the composition of each thin film and use Raman spectra peak full width at half maximum (FHWM) to appraise their crystalline quality.
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WU, SHU-WEI, and 吳書緯. "Optical properties of ZnO epilayers and InGaN/GaN mulitiple-quantum-well light emitting diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/25041550914615132975.
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碩士中原大學
應用物理研究所
96
We studied the optical properties of the InGaN/GaN mulitiple-quantum-well light emitting diodes (LEDs) and ZnO epilayers. Using photoconductivity and photoluminescence, the carrier escape efficiency and nonradiative efficiency of the InGaN/GaN multiple-quantum-well LEDs can be obtained. The electroluminescence (EL) intensity of the InGaN/GaN mulitiple-quantum-well LEDs is increased by about 1.1-2.1 times after incorporation of the gold nanoclusters. It is found the experimental enhancement of luminescence is in good agreement with the simulated result from the Mie scattering. We therefore suggest the scattering of the gold nanoclusters is responsible for the enhancement of EL. We also studied the energy relaxation of hot electrons in ZnO epilayers using PL. The measured electron temperature variation with different electric fields can be explained by two different models based on the energy relaxation of electrons due to LO phonon and acoustical phonon scattering. We find the energy relaxation of the hot electrons in ZnO epilayers is dominated by the acoustics phonon scattering at low temperature. As the temperature increases, the LO phonon scattering plays an important role in the energy relaxation of the hot electrons gradually.
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Lee, Jiann-Jie, and 李建階. "The Stimulated Emission Processes for Zn1-XCdXSe/ZnSe Mutli-Quantum Well." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/53941460447459951907.
Full textAbstract:
博士淡江大學
物理學系
87
The advantages of semiconductor laser are (Ⅰ)small volume、(Ⅱ) low driven current、(Ⅲ) variable wavelengths、(Ⅳ) high electro-opto conversion efficiency and (Ⅴ)productive. Semiconductor laser mostly operated at red or infrared wavelengths in modern products, and it is not practically at short blue-green wavelengths. Because the density of storage data in CD is decided by wavelength for physical applications, so, the important goal of applications is to pursue an compactly short wavelength laser. Especially, blue-green semiconductor laser become the most popular objects of research. The stimulated emission mechanism of Ⅱ-Ⅵ semiconductor superlattice are (1)phase space filling by Ding et al.、(2)inelastic exciton-exciton scattering by Jen-Y Jen、and(3)localized biexciton by Kreller. They all claimed that their mechanisms played an important role for lasing, but, the relations between them are still under debate. The purpose of this study is to explain the stimulated emission processes of Zn1-XCdXSe/ZnSe Mutli-Quantum Well, whose wavelengths are at blue-green. For this study, we used Zn1-XCdXSe/ZnSe MQW, which is optimized with x=0.3,for well widths Lw ranging between 20 and 112 A, and barrier widths Lb ranging between 20 and 60 A. The samples investigated in this study were analyzed by X-ray diffraction, in order to test the periodical structure and decide the widths of well (Lw) and barrier(Lb) . For measurements of spontaneous emission of various widths, we observed spectra toward high energy when oscillator strength higher by quantum confinement of narrow well widths. And FWHM (full width of half maximun) broad by fluctuations of well widths. The variations of spontaneous emission, with increasing temperature allows narrowing of energy gap, lead to a shift of low energy side of the spectrum. Because of the exciton-LO-phonon scattering, the FWHM is broad with increasing temperature.
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Stölzel, Marko. "Photolumineszenz von Exzitonen in polaren ZnO/MgZnO-Quantengrabenstrukturen." Doctoral thesis, 2013. https://ul.qucosa.de/id/qucosa%3A12679.
Full textAbstract:
Die vorliegende Arbeit befasst sich mit dem vertieften Verständnis der Rekombinationsdynamik von polaren ZnO/MgZnO-Quantengraben(QW)-Strukturen zur exakten Bestimmung des unabgeschirmten Grundzustandes und der Analyse der zugrundeliegenden Emissionsprozesse. Dafür werden ausgehend von Beobachtungen an ZnO-Dünnschichten die Eigenschaften von mittels PLD hergestellten QWs unter dem Einfluss des internen elektrischen Feldes mit Hilfe der zeitintegrierten (TI-) und zeitaufgelösten (TR-) Photolumineszenz(PL)-Spektroskopie untersucht.
Die Differenz der spontanen und piezoelektrischen Polarisation zwischen ZnO und MgZnO führt zur Ausbildung eines internen elektrischen Feldes und damit zum Auftreten des quantum-confined Stark effect (QCSE). Es wird gezeigt, dass der QCSE durch eine Durchmischung der Grenzflächen stark vermindert wird. Für QWs mit schwachem QCSE ist die Übergangsenergie und Zerfallszeit des Grundzustandes experimentell gut bestimmbar. Bei starkem QCSE müssen jedoch bereits bei geringen Anregungsdichten (1E10 /cm²) Abschirmeffekte berücksichtigt werden. Dadurch ist es sehr schwierig, den unabgeschirmten Grundzustand mittels herkömmlicher experimenteller Methoden mit einem aussagekräftigen Signal-Rausch-Verhältnis zu bestimmen. Es wird gezeigt, dass für QWs mit einer Dicke > 4 nm die Übergangsenergie des unabgeschirmten Grundzustandes nicht durch TI-PL-Messungen bestimmt werden kann. TR-PL-Messungen zeigen energetisch tiefere Übergangsenergien, jedoch ebenfalls nicht den unabgeschirmten Grundzustand. Mit einem eingeführten Modell zur Beschreibung der zeitabhängigen Abschirmung des Grundzustandsniveaus wird die Zerfallszeit für QW-Dicken in einem Bereich von 1 - 10 nm bestimmt. Durch die selbstkonsistente Lösung von Schrödinger- und Poissongleichung werden die Übergangsenergie und Zerfallszeit der Exzitonen im QW in Abhängigkeit der Feldstärke und auch der Ladungsträgerdichte berechnet. Dadurch ist eine exaktere Bestimmung der Feldstärke möglich. Zusätzlich wird durch die vergleichende Untersuchung von QWs unterschiedlicher Dicke, Potentialhöhe und Wachstumsunterlage die spontane und piezoelektrische Polarisation der Materialien experimentell bestimmt.
Mittels temperaturabhängiger Messungen wird der Ursprung der Lumineszenz für QW-Dicken > 2 nm der Rekombination freier Exzitonen im QW zugeschrieben. Für dünnere QWs ist der temperaturabhängige Verlauf des PL-Maximums durch Lokalisation der Exzitonen bestimmt.
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Chung, Wei-Lun, and 鍾瑋倫. "Study of the Emission Characteristics of InGaN/GaN and CdZnO/ZnO Quantum-well Structures with the Photoluminescence Spectroscopy." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/68121361003673456983.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
100
In this study, we demonstrate the emission characteristics in InGaN/GaN QWs and in CdZnO/ZnO QWs with photoluminescence measurements. First, temperature-dependent photoluminescence and excitation power-dependent photoluminescence are performed on InGaN/GaN QWs with an InGaN-based diode laser (λ=406nm). The counteraction between the increased carrier localization effect in the QWs, which is caused by the thermal annealing process, and the enhanced quantum-confined Stark effect in the QWs, which is caused by the increased piezoelectric field, when the different thickness of p-type layer is grown at a high temperature on the InGaN/GaN QWs is illustrated. Next, we demonstrate the results of temperature-dependent photoluminescence and excitation power-dependent photoluminescence with a He-Cd laser (λ=325nm) to understand the emission behaviors of the CdZnO/ZnO QW on GaN and ZnO templates. With two-Gaussion fitting, wurtzite CdZnO structure and rock-salt CdZnO structure exist in the CdZnO well layers. The rock-salt structures may dominate over the wurtzite structures in photoluminescence intensity when the total Cd content is high.
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Huang, Yu-Cheng, and 黃鈺程. "The optical properties of nonpolar ZnO/MgZnO quantum well on m-plane sapphire grown by pulsed laser deposition." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/22977684875681069652.
Full textAbstract:
碩士國立交通大學
影像與生醫光電研究所
101
This thesis report the experimental study of nonpolar ZnO/MgZnO multiple quantum wells (MQWs) on m-plane sapphire by pulsed laser deposition. The nonpolar MQWs were fabricated on the m-ZnO buffer by two-step growth, which effectively reduces the ratio of extra domain and surface roughness but produces high basal-plane stacking faults (BSF) density. So, the photoluminescence (PL) spectra, shows not only a blueshift near-band edge (NBE) emission but strong stacking faults emissions from QWs, We also investigated exciton and LO-phonon coupling and exction binding energy for each sample, the results indicated quantum confinement effect play a dominant role. In addition, the NBE emission are all located above 3.36 eV even for the well width reaching 16 nm consist with the theoretical excitonic transition energies with no internal electric field, and the fixed peak of power-dependent LT-PL, those exhibits evidences of the absence of quantum-confined Stark effect in these samples. The fabrication of nonpolar MQW is successful and optical properties shows not only possess the quantum confinement effect but also prevent from the QCSE.
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Shih, Tsai-Hsuen, and 施采萱. "Optical Properties of Zn1-xCdxSe Epilayers and ZnSe/ Zn1-xCdxSe Multiple Quantum Well Grown by Molecular Beam Epitaxy." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/61973364057221524901.
Full textAbstract:
碩士中原大學
應用物理研究所
90
Zn1-xCdxSe epilayers were grown on (100) GaAs substrates by molecular beam epitaxy. Lattice constants of the epilayers were measured by the (004) rocking curve X-ray diffraction. Full width at half maximum (FWHM) of 475 to 2100 arcsec was obtained. Temperature dependence of energy gap, measured by the photoluminescence (PL) spectra, was fitted by the Varshni’s and O’Donnell’s models. Phonon energy related fitting parameters β (161K to 368K) and
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Chen, Kuo-Yu, and 陳國裕. "Enhanced optical properties of CdSe/ZnS nanoparticles by using InGaN/GaN Multiple Quantum Wells and metal films." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/14177420409189009398.
Full textAbstract:
碩士國立臺灣大學
物理研究所
96
By combining InGaN/GaN (MQWs) multiple quantum wells with different thickness of metal films, we have investigated the change of optical properties of CdSe/ZnS quantum dots. It is found that the photoluminescence intensity of CdSe/ZnS quantum dots can be enhanced by up to 4 times. The underlying mechanism arises from the combined effect of Förster resonance energy transfer and surface plasmon resonance. Our result is useful for the creation of highly efficient solid state emitters.
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Cheng, Chih-Chuan, and 鄭志權. "Molecular beam epitaxy and physical properties of Zn1-xMnxSe╱ZnSe1-yTey multiple quantum well." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/02410073206347323500.
Full textAbstract:
碩士中原大學
應用物理研究所
89
In this thesis, Zn1-xMnxSe∕ZnSe1-yTey quantum well structures were grown by molecular beam epitaxy. Low temperature photoluminescence was used to study the optical properties. Under the quantum confinement of Zn1-xMnxSe∕ZnSe1-yTey quantum well structure, the transition energies of Te cluster and Ten (n≧2) bound exciton decrease with well width. Type II band alignment of Zn1-xMnxSe∕ZnSe1-yTey quantum well structure is determined. At last, the confinement energies of electron and hole were also calculated. The experimental quantum confinement energies of Te cluster bound exciton can be fitted by theoretical value reasonabbly. The respective valence and conduction band offset of Zn0.97Mn0.03Se∕ZnSe0.92Te0.08 quantum well are determined to be 350±50meV/205±50 meV.