Dissertations / Theses: 'UV photodetector'

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Goulty, Duncan N. O. "Photodetector calibration for solar SXR and UV dose measurement for correlation with materials degradation on the international space station." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438511.

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Bueno, Hernandez Diana. "Optical and electrochemical sensing methods for the detection of food contaminants." Thesis, Perpignan, 2016. http://www.theses.fr/2016PERP0044/document.

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Un appareil de mesure de la fluorescence, à faible coût et portable a été développé pour quantifier les concentrations d’Ochratoxine A (OTA) dans des échantillons réels. Le système est basé sur l’excitation par une UV-LED à 365 nm et un photo détecteur contrôlé par une interface dans LabVIEW. Aussi, une image capteur, CMOS, contrôlée par une interface conçue dans MATLAB. L’OTA est une molécule naturellement fluorescente. Après excitation par une UV-, l’image de la fluorescence émise est captée par une caméra et traitée en vue de la mesure de la concentration de l’OTA. Le système d’analyse a été basé sur les 3 composants rouge, vert et bleu (RGB, selon l'acronyme anglais). La gamme est linéaire entre de 2-40 µg/L. L’extraction de l’OTA est réalisée par des colonnes d'immuno affinité (IAC, selon l'acronymeanglais) et les colonnes à empreinte moléculaire (MIP, selon l'acronyme anglais) pour les échantillons de cacao, de la bière et du vin. Les résultats obtenus ont été validés par la méthode chromatographique (HPLC). L'appareil conçu est facile à utiliser, économique et portable. En outre, l'utilisation des nouvelles technologies a été inclus tels que l'emploi du smartphone pour détecter l'OTA et la création d'un APP. Des données d'image de fluorescence provenant de la caméra du smartphone et sont analysées par un ordinateur personnel et présentés dans les composantes RGB, où l'image est envoyée à l'ordinateur par WIFI et le téléphone intelligent est utilisé comme source d'énergie trop. Enfin, une APP pour le système Android a été créé pour capturer l'image et fournit les valeurs RGB. Enfin l'utilisation du traitement de l'image a été utilisée pour quantifier l'OTA dans les échantillons réels sans colonnes IAC ou MIP, employée pour extraire la mycotoxine. L’analyse a été réalisée par des techniques colorimétriques et d’analyse de la couleur
A portable and low cost fluorescence set-up to quantify the concentrations of Ochratoxin A(OTA) in real samples was developed. The detection through the device consist of anultraviolet light at 365 nm and an photo detector or a CMOS sensor controlled by anexecutable interface designed in LabVIEW or MATLAB. It has been reported that OTA is naturally fluorescent, so it allows the user to get a UV LED to excite the sample, get a value involtage when a photodetector is employed or a photograph of the OTA under excitationconditions, and process that image in order to predict the concentrations of the sample. Tocapture and process the image, in an automatically manner, the system was completely basedon the Red, Green and Blue (RGB) components. The linearity for OTA obtained in the rangeof concentrations corresponds to 2-40 µg/L. Immunoaffinity columns (IAC) and molecularimprinted polymer columns (MIP) were used with cocoa, beer and wine samples. Theobtained results were cross-validated using chromatographic method such as HPLC and theFluoroskan equipment. The developed setup is easy to use, economical and portable. Besides,the use of new tendencies was included such as employ the smartphone to detect OTA and thecreation of an APP. Fluorescence image data from the smartphone camera are analyzed by apersonal computer and presented in RGB components, where the image is sent to thecomputer by WIFI and the smartphone is used as a power source too. Finally, an APP forandroid system was created to capture the image and provides the RGB values. At the end, theuse of image processing to quantify the OTA in real samples without incorporated IAC or MIPcolumns to extract the mycotoxin from a complex solution, employing colorimetric techniquesand color analysis

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Cheak, Seck Fai. "Detecting near-UV and near-IR wavelengths with the FOVEON Image Sensor /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FCheak.pdf.

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Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, Dec. 2004.
Thesis Advisor(s): Gamani Karunasiri, Richard C. Olsen. Includes bibliographical references (p. 57-60). Also available online.

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Amor, Sarrah. "Étude des défauts dans les alliages de semi-conducteurs à grand gap B(AlGa)N et de leur rôle dans les propriétés de transport : application aux photo-détecteurs U." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0286/document.

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Le nitrure de gallium (GaN) et ses alliages ternaires et quaternaires suscitent de plus en plus d’intérêt dans les communautés scientifiques et industrielles pour leur potentiel d’utilisation dans des dispositifs électroniques haute fréquence, dans les transistors à forte mobilité électroniques, dans la photo-détection UV et les cellules solaires de nouvelles générations. L’aboutissement de ces nouveaux composants reste entravé à l’heure actuelle, entre autre, par la non maîtrise des techniques d’établissement de contacts électriques. C’est dans ce cadre général que s’inscrivent les travaux de cette thèse. Même si l’objectif principal de cette thèse concerne l’étude des défauts électriquement actifs dans les alliages de semiconducteurs à grand gap B(AlGa)N et de leur rôle dans les propriétés de transport, la réalisation des contacts ohmiques et des contacts Schottky constitue une étape essentielle dans la réalisation des dispositifs à étudier. Pour les contacts ohmiques, nous avons déposé des couches de type Ti/Al/Ti/Au (15/200/15/200) par évaporation thermique. Des résistances spécifiques des contacts de l’ordre de 3x10-4Wcm2 ont été déterminées par les méthodes des TLM linéaires et confirmées par les TLM circulaires. Une modélisation théorique a été entreprise dans ce sens pour analyser les mesures expérimentales. Ensuite on a réalisé des diodes Schottky en déposant des contacts métalliques de Platine (Pt) d’épaisseur 150 nm. Des facteurs d’idéalité de 1.3 et une hauteur de barrière de 0.76 eV ont été obtenus et d’une manière reproductible. Une fois ces dispositifs réalisés, une étude des mécanismes de transport a été entreprise et nous a permis de mettre en évidence l’existence des effets tunnel direct et assisté par le champ, en plus de l’effet thermoïonique classique. Ceci a été mis en évidence par des mesures de courant et de capacité en fonction de la température. Pour les photodétecteurs, nous avons réalisés les mêmes mesures de courant et de capacité à l’obscurité et sous illumination à des longueurs d’ondes adaptées. Ces mesures nous ont permis de comprendre les phénomènes de gain qu’on a observés sur ces échantillons et aussi de mettre en évidence des mécanismes thermiquement actifs, dont les énergies d’activation ont été déterminées par la technique de l’Arrhenius. L’étude des défauts électriquement actifs a été menée par la technique transitoire de capacité de niveaux profonds, la (DLTS). Cette technique a été récemment mise en oeuvre au laboratoire et nous a permis d’effectuer des mesures sous différentes conditions incluant diverses polarisations de repos, différentes fréquences, et différentes hauteurs et largeurs d’impulsion de polarisation. Un des résultats importants est la possibilité de caractérisation à la fois des pièges à majoritaires et des pièges à minoritaire en changeant simplement les conditions de polarisation et contrairement aux procédures habituelles où une excitation optique supplémentaire est souvent nécessaire pour augmenter la concentration des porteurs minoritaires. Il a ainsi été mis en évidence, en accord avec la plupart des résultats de la littérature, l’existence de 6 pièges à électrons, tous situés en dessous de 0.9 eV de la bande de conduction, de trois pièges à trous dans l’intervalle 0.6 - 0 .7 eV au dessus de la bande de valence et un piège à trous distribué à l’interface. Une procédure rigoureuse de fit a été mise au point et a permis de confirmer nos résultats obtenus par la procédure classique de l’Arrhenius
Gallium nitride (GaN) and its ternary and quaternary alloys are attracting more and more interest in the scientific and industrial communities for their potential for use in high frequency electronic devices, for transistors with high electronic mobility, for UV photo-detection and new-generation solar cells. The outcome of these new components is still be seen to be limited in many areas, mainly due to the lack of control of electrical contacts implementation techniques. It is in this context that this thesis takes place.Although the main objective of this thesis deals with the study of the electrically active defects in high band gap B(AlGa)N semiconductor alloys and their role in the transport properties, the production of ohmic and Schottky contacts is an essential step in the realization of the devices under study. For the Ohmic contacts, we have deposited Ti/Al/Ti/Au (15/200/15/200) layers by thermal evaporation. Using the Transfer Length Method (TLM), we obtained specific contact resistances in the order of 3x10-4Wcm2. The Circular TLM has also confirmed this result. Besides, a theoretical modelling has been carried out to analyse the experimental measurements. Schottky diodes were then produced by depositing 150 nm platinum (Pt) metal contacts. An ideality factor of 1.3 and a barrier height of 0.76 eV were obtained. On the other hand, a study of transport mechanisms has been performed. It allowed us to demonstrate the existence of the direct tunnelling and the Thermionic Field Emission, in addition to the conventional thermionic effect. This result was underpinned by current and capacity measurements as a function of temperature. For photo detectors, we performed the same measurements of current and capacity in darkness and under illumination at suitable wavelengths. These measurements allowed understanding the internal gain that was observed on the samples. Furthermore, they show the effect of the thermally active mechanisms whose activation energies were determined by the Arrhenius technique. Using the Deep-Level Transient Spectroscopy (DLTS) technique followed up the study of the electrically active defects. This technique has recently been implemented in the laboratory. It allowed us to perform measurements under different conditions including various reverse bias, different frequencies, and different voltage pulse amplitudes and durations. One of the important results is the possibility of characterizing both majority and minority traps by simply changing the polarization conditions, as opposed to the usual procedures where an additional optical excitation is often necessary to increase the concentration of the minority carriers. In accordance with most of the encountered literature results, we found 6 electron traps all located below 0.9 eV of the conduction band, 3 hole traps in the 0.6-0.7 eV range above the valence band and one hole trap distributed at the interface. A rigorous procedure was developed and confirmed our results obtained by the standard Arrhenius technique

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Biondo, Stéphane. "Simulation, réalisation et caractérisation de jonction p+n en SiC-4H, pour la photodétection de rayonnement UV." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4340.

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Le SiC est un matériau semi-conducteur à large bande d'énergie interdite dont les très bonnes caractéristiques électriques et thermiques en font un candidat idéal pour la fabrication de composants dans le domaine de la puissance et des détecteurs de rayonnement. En particulier, la réalisation de détecteurs UV est très attendue dans les domaines suivants : détection d'incendies, imagerie de surface, astronomie, médecine, militaire… Les photodétecteurs à base de semiconducteurs à large bande interdite permettent d'obtenir une très bonne sélectivité dans l'UV, sans avoir à utiliser de filtres optiques. Le SiC semble être le matériau le plus prometteur, grâce à sa bonne stabilité chimique, mécanique et thermique, ce qui représente un avantage pour opérer en environnement extrême. Cependant le dopage du SiC nécessite un savoir-faire très particulier (implantation à chaud, recuit à haute température, forte dynamique de chauffe…). Nous nous sommes proposés dans un premier temps de réaliser par implantation (ionique et plasma) des composants tests, permettant d'accéder aux caractéristiques des jonctions. Le cas des jonctions implantées n+p et p+n a été étudié. Après l'optimisation des paramètres technologiques de l'implantation et du recuit associé, la fabrication de détecteurs de rayonnement basés sur la diode Schottky ou la diode p.n a été mise en œuvre. Une étape de simulation de ces composants a été effectuée sur le logiciel Sentaurus Device (Synopsys). Les caractérisations de ces détecteurs ont montré une meilleure sensibilité pour les diodes implantées Bore par plasma
Silicon carbide is a wide band-gap semiconductor with electrical and thermal characteristics particularly suitable for high power devices and radiation sensors. The realisation of UV detectors is mainly useful in the following sectors: fire detection, surface imagery, astronomy, medicine, military... The photodetectors based on wide band-gap semiconductors allow to get a very good selectivity, without using optical filters. Silicon carbide seems to be the most promising material, due to its chemical, mechanical and thermal stability, inducing a reliable behaviour in extreme environment. However SiC doping requires a distinct know-how (hot ion implantation, high temperature annealing, rapid heating-rate…). Test devices have been firstly processed by using ion implantation and plasma, allowing evaluating p+n or n+p junction characteristics. After the optimisation of the technological parameters of implantation and related annealing, the realisation of radiation detectors based on Schottky or p.n diodes has been carried out. The electrical simulations of such devices were performed with Sentaurus Devices program (Synopsys). The characteristics of the devices proved an improvement with the Boron-plasma implantation

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Cossuet, Thomas. "Problématique de la polarité dans les nanofils de ZnO localisés, et hétérostructures reliées pour l’opto-électronique." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI086/document.

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Le développement d’architectures nanostructurées originales composées de matériaux abondants et non-toxiques fait l’objet d’un fort intérêt de la communauté scientifique pour la fabrication de dispositifs fonctionnels efficaces et à bas coût suivant des méthodes d’élaborations faciles à mettre en œuvre. Les réseaux de nanofils de ZnO élaborés par dépôt en bain chimique sont, à ce titre, extrêmement prometteurs. L’étude des propriétés de ces réseaux de nanofils et leur intégration efficace au sein de dispositifs nécessitent toutefois un contrôle avancé de leurs propriétés structurales et physiques, notamment en terme de polarité, à l’aide de techniques de lithographies avancées.Le dépôt en bain chimique des nanofils de ZnO est d’abord effectué sur des monocristaux de ZnO de polarité O et Zn préparés par lithographie assistée par faisceau d’électrons. Par cette approche de croissance localisée, un effet significatif de la polarité des nanofils de ZnO est mis en évidence sur le mécanisme de croissance des nanofils, ainsi que sur leurs propriétés électriques et optiques. La possibilité de former des nanofils de ZnO sur des monocristaux de ZnO semipolaires nous a de plus permis d’affiner la compréhension de leurs mécanismes de croissance sur les couches d’amorces polycristallines de ZnO. Par la suite, le dépôt des nanofils de ZnO en bain chimique est développé sur des couches d’amorces polycristallines de ZnO préparés à l’aide de la lithographie assistée par nano-impression. Suivant cette approche, des réseaux de nanofils de ZnO localisés sont formées sur de grandes surfaces, ce qui permet d’envisager leur intégration future au sein de dispositifs fonctionnels.Les nanofils de ZnO sont ensuite combinés avec des coquilles semiconductrices de type p par des méthodes de dépôt chimique en phase liquide ou en phase vapeur afin de fabriquer des hétérostructures cœurs-coquilles originales. Le dépôt de couches successives par adsorption et réaction (SILAR) d’une coquille absorbante de SnS de phase cubique est optimisé sur des nanofils de ZnO recouverts d’une fine couche protectrice de TiO2, ouvrant la voie à la fabrication de cellules solaires à absorbeur extrêmement mince. Enfin, un photo-détecteur UV autoalimenté prometteur, présentant d’excellentes performances en termes de réponse spectrale et de temps de réponse, est réalisé par le dépôt chimique en phase vapeur d’une coquille de CuCrO2 sur les nanofils de ZnO
Over the past decade, the development of novel nanostructured architectures has raised increasing interest within the scientific community in order to meet the demand for low-cost and efficient functional devices composed of abundant and non-toxic materials. A promising path is to use ZnO nanowires grown by chemical bath deposition as building blocks for these next generation functional devices. However, the precise control of the ZnO nanowires structural uniformity and the investigation of their physical properties, particularly in terms of polarity, remain key technological challenges for their efficient integration into functional devices.During this PhD, the chemical bath deposition of ZnO nanowires is combined with electron beam lithography prepared ZnO single crystal substrates of O- and Zn-polarity following the selective area growth approach. The significant effects of polarity on the growth mechanism of ZnO nanowires, as well as on their electrical and optical properties, are highlighted by precisely investigating the resulting well-ordered O- and Zn-polar ZnO nanowire arrays. An alternative nano-imprint lithography technique is subsequently used to grow well-ordered ZnO nanowire arrays over large areas on various polycrystalline ZnO seed layers, thus paving the way for their future integration into devices. We also demonstrate the possibility to form ZnO nanowires by chemical bath deposition on original semipolar ZnO single crystal substrates. These findings allowed a comprehensive understanding of the nucleation and growth mechanisms of ZnO nanowires on polycrystalline ZnO seed layers.In a device perspective, the ZnO nanowires are subsequently combined with p type semiconducting shells by liquid and vapor chemical deposition techniques to form original core-shell heterostructures. The formation of a cubic phase SnS absorbing shell is optimized by the successive ionic layer adsorption and reaction (SILAR) process on ZnO nanowire arrays coated with a thin protective TiO2 shell, which pave the way for their integration into extremely thin absorber solar cells. A self-powered UV photo-detector with fast response and state of the art performances is also achieved by the chemical vapor deposition of a CuCrO2 shell on ZnO nanowire arrays

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Östlund, Ludwig. "Fabrication and Characterization of Micro and Nano Scale SiC UV Photodetectors." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-52911.

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The focus of this master thesis work is on the fabrication of micro- and nano-scale metalsemiconductor-metal silicon carbide (SiC) UV photodetectors and subsequent electrical and optical evaluation of the fabricated devices. The UV photodetectors have significant potential to address the needs of many applications such as detection of corona discharge and flames, industrial machine viewing, and bacteria in water or paper mills. Micro-scale devices in 4H-SiC and 6H-SiC have been fabricated successfully with good photoresponse and low dark current. Reduction in size of the 4H-SiC UV detectors from micro-scale to nano-scale has been achieved by the use of nano imprint lithography (NIL). The performance of these nano-devices have been characterized, and experiment results reveal good photo sensitivity at very low applied biases.

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Pereira, Fábio André Barbosa. "Study and development of UV photodetectors envisaging COMPASS RICH-1 upgrade and applications." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/15910.

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Doutoramento em Engenharia Física
COMPASS is an experiment at CERN’s SPS whose goal is to study hadron structure and spectroscopy. The experiment includes a wide acceptance RICH detector, operating since 2001 and subject to a major upgrade of the central region of its photodetectors in 2006. The remaining 75% of the photodetection area are still using MWPCs from the original design, who suffer from limitations in gain due to aging of the photocathodes from ion bombardment and due to ion-induced instabilities. Besides the mentioned limitations, the increased luminosity conditions expected for the upcoming years of the experiment make an upgrade to the remaining detectors pertinent. This upgrade should be accomplished in 2016, using hybrid detectors composed of ThGEMs and MICROMEGAS. This work presents the study, development and characterization of gaseous photon detectors envisaging the foreseen upgrade, and the progress in production and evaluation techniques necessary to reach increasingly larger area detectors with the performances required. It includes reports on the studies performed under particle beam environment of such detectors. MPGD structures can also be used in a variety of other applications, of which nuclear medical imaging is a notorious example. This work includes, additionally, the initial steps in simulating, assembling and characterizing a prototype of a gaseous detector for application as a Compton Camera.
O COMPASS é uma experiência no SPS do CERN cujo objectivo é estudar a espectroscopia hadrónica e a estrutura dos nucleões. A experiência inclui um detector RICH de larga aceitação, operacional desde 2001 e sujeito a um upgrade de parte dos seus fotodetectores em 2006. Os restantes 75% da área de fotodetecção ainda utilizam as MWPCs do desenho original, que sofrem de limitações de ganho devido ao envelhecimento dos fotocátodos pelo bombardeamento com iões e a instabilidades por eles induzidas. Além destas limitações, o aumento de luminosidade expectável nos próximos anos para a experiência tornam o upgrade dos restantes fotodetectores desejável. Este upgrade deverá acontecer em 2016 e deverá fazer uso de detectores híbridos compostos por ThGEMs e MICROMEGAS. Este trabalho apresenta o estudo, desenvolvimento e caracterização de fotodetectores gasosos com vista ao upgrade referido, e o progresso na produção e nas técnicas de avaliação necessário para alcançar as maiores áreas de detecção com os desempenhos exigidos. Inclui também a descrição e tratamento de exercícios com irradiação por feixe de partículas dos detectores em causa. Os MPGDs podem também ser usados em várias outras aplicações, entre as quais se destaca a imagiologia médica nuclear. Este trabalho inclui, adicionalmente, as etapas iniciais de simulação, montagem e caracterização de um protótipo de detector gasoso para aplicação como Câmara Compton.

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Mallampati, Bhargav. "Development of High Gain Ultraviolet Photo Detectors Based on Zinc Oxide Nanowires." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500106/.

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Semiconductor nanowires acts as an emerging class of materials with great potential for applications in future electronic devices. Small size, large surface to volume ratio and high carrier mobility of nanowires make them potentially useful for electronic applications with high integration density. In this thesis, the focus was on the growth of high quality ZnO nanowires, fabrication of field effect transistors and UV- photodetectros based on them. Intrinsic nanowire parameters such as carrier concentration, field effect mobility and resistivity were measured by configuring nanowires as field effect transistors. The main contribution of this thesis is the development of a high gain UV photodetector. A single ZnO nanowire functioning as a UV photodetector showed promising results with an extremely high spectral responsivity of 120 kA/W at wavelength of 370 nm. This corresponds to high photoconductive gain of 2150. To the best of our knowledge, this is the highest responsivity and gain reported so far, the previous values being responsivity=40 kA/W and gain=450. The enhanced photoconductive behavior is attributed to the presence of surface states that acts as hole traps which increase the life time of photogenerated electrons raising the photocurrent. This work provides the evidence of such solid states and preliminary results to modify the surface of ZnO nanowire is also produced.

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Chey, Chan Oeurn. "Synthesis of ZnO and transition metals doped ZnO nanostructures, their characterization and sensing applications." Doctoral thesis, Linköpings universitet, Fysik och elektroteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-113237.

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Nanotechnology is a technology of the design and the applications of nanoscale materials with their fundamentally new properties and functions. Nanosensor devices based on nanomaterials provide very fast response, low-cost, long-life time, easy to use for unskilled users, and provide high-efficiency. 1-D ZnO nanostructures materials have great potential applications in various sensing applications. ZnO is a wide band gap (3.37 eV at room temperature) semiconductor materials having large exciton binding energy (60 meV) and excellent chemical stability, electrical, optical, piezoelectric and pyroelectric properties. By doping the transition metals (TM) into ZnO matrix, the properties of ZnO nanostructures can be tuned and its room temperature ferromagnetic behavior can be enhanced, which provide the TM-doped ZnO nanostructures as promising candidate for optoelectronic, spintronics and high performance sensors based devices. The synthesis of ZnO and TM-doped ZnO nanostructures via the low temperature hydrothermal method is considered a promising technique due to low cost, environmental friendly, simple solution process, diverse 1-D ZnO nanostructures can be achieved, and large scale production on any type of substrate, and their properties can be controlled by the growth parameters. However, to synthesize 1-D ZnO and TM-doped ZnO nanostructures with controlled shape, structure and uniform size distribution on large area substrates with desirable properties, low cost and simple processes are of high interest and it is a big challenge at present. The main purpose of this dissertation aims to develop new techniques to synthesize 1-D ZnO and (Fe, Mn)-doped ZnO nanostructures via the hydrothermal method, to characterize and to enhance their functional properties for developing sensing devices such as biosensors for clinical diagnoses and environmental monitoring applications, piezoresistive sensors and UV photodetector. The first part of the dissertation deals with the hydrothermal synthesis of ZnO nanostructures with controlled shape, structure and uniform size distribution under different conditions and their structural characterization. The possible parameters affecting the growth which can alter the morphology, uniformity and properties of the ZnO nanostructures were investigated. Well-aligned ZnO nanorods have been fabricated for high sensitive piezoresistive sensor. The development of creatinine biosensor for clinical diagnoses purpose and the development of glucose biosensor for indirect determination of mercury ions for an inexpensive and unskilled users for environmental monitoring applications with highly sensitive, selective, stable, reproducible, interference resistant, and fast response time have been fabricated based on ZnO nanorods. The second part of the dissertation presents a new hydrothermal synthesis of (Fe, Mn)-doped-ZnO nanostructures under different preparation conditions, their properties characterization and the fabrication of piezoresistive sensors and UV photodetectors based devices were demonstrated. The solution preparation condition and growth parameters that influences on the morphology, structures and properties of the nanostructures were investigated. The fabrication of Mn-doped-ZnO NRs/PEDOT:PSS Schottky diodes used as high performance piezoresistive sensor and UV photodetector have been studied and Fe-doped ZnO NRs/FTO Schottky diode has also been fabricated for high performance of UV photodetector. Finally, a brief outlook into future challenges and relating new opportunities are presented in the last part of the dissertation.

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Chen, Wei-Ming, and 陳偉銘. "ZnS/ZnO nanobilayers based-UV photodetector." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/m3eed7.

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碩士
國立臺北科技大學
製造科技研究所
106
Recently, chemical, biological, gas and ultraviolet (UV) sensors with modern nanostructures have been widely fabricated and investigated due to their unique structural and optical properties. Moreover, zinc sulfide (ZnS) films are of great importance for applications in various optoelectronic devices. Compared with direct band gap semiconductor ZnO (~3.4 eV), ZnS has a higher band gap (3.7 eV in cubic zinc blende phase) as a UV detector in this specific wavelength region. In addition, ZnS with advantage of a diverse range of possible structures and morphologies, therefore provides a novel prospective alternative for UV detectors that would be particularly useful in the region of UV-A (~320-400 nm) band. In this study, ZnS and ZnS/ZnO nanobilayers were prepared by radio frequency (RF) magnetron sputtering. Firstly, ZnS films were deposited onto Si (100) substrate with different sputtering power ranged of 50-150 W under working pressure of 10 mtorr. From the resaults, ZnS thin films exhibited a good crystallinity with (111) preferred orientation, and the intensity of ZnS (111) diffraction peak increased with increasing the sputtering power. The UV detector with ZnS sensing layer which were deposited with sputtering power of 150 W exhibits better operating stability. Secondly, ZnS films were deposited onto ZnO and Si (100) substrate under working pressure of 10 mtorr with different sputtering power of 50 W, 75 W, 100 W, 125 W and 150 W, respectively. The thickness of ZnS and ZnO films was fixed at 100 nm. As shown in the XRD patterns, the crystallinity of the ZnS was improved with increasing RF power ranged from 50 W to 150 W. On the other hand, it can be observed that the grain size of ZnS/ZnO nanobilayers increased with increasing the sputtering power as shown in the FE-SEM plan-view images. Moreover, the performance of ZnS/ZnO nanobilayered UV detector enhancement can be attributed to passivation effect on ZnS/ZnO nanobilayers. The band structure has been modified and leaded to the spatial separation of charge carriers. This phenomenon not only enhanced their charge carrier transport characteristics by confining the electrons and reducing surface states in the ZnO channel but also increased the photocurrent under ultraviolet illumination by reduceing the recombination probability of the photogenerated charge carriers. It can be expected that the ZnS/ZnO nanobilayers provide versatility to realize multifunctional nanoscaled electronic devices with fast switching speeds and high photosensitivity for the next generation electronic devices.

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Huang, Yu-Chun, and 黃友俊. "Laterally Bridged ZnO Nanorod UV Photodetector Applications." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/b7b2k5.

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碩士
國立雲林科技大學
電子工程系
102
This study develops a density-controlled and seedless pressure growth method for laterally bridged ZnO nanorods from Au electrode for use in metal–semiconductor–metal photodetector fabrication. Firstly, directly grown laterlly ZnO nanorods on the Au electrode. Secondly, Using the different annealing time for Au electrode, the effect of pre-annealing process on suppressing vertical ZnO nanorods is systematically investigated by atomic force microscopy and scanning electron microscopy. The pre-annealing process is demonstrated to have direct influence on controlling vertical/lateral ZnO nanorod density and morphology. Interlaced and density-controlled ZnO nanorods with approximate single-crystalline structure can be directly grown from the side wall of pre-annealed Au electrode fingers without seed-layer. Through pre-annealing process, dark-current can be decreased three orders with an applied voltage of 1 V. Highly dense lateral ZnO nanorod-based photodetectors produce remarkable responsivity of 7.01 × 103 A/W and UV/visible rejection ratio of 281.21. Moreover, high internal photoconductive gain (104–105) exists in the fabricated photodetectors. For a given bandwidth of 10 k Hz and 1 V applied bias, the low-frequency noise spectra obtained from the UV photodetector were caused purely by the 1/f noise. The noise equivalent power of photodetectors with 0, 10, and 20 min pre-annealing periods are estimated to be 3.58 × 10−13, 6.78 × 10−13, and 4.86 × 10−13 W, and correspond to normalized detectivity of 1.85 × 1012, 1.17 × 1012, and 1.99 × 1012 cm Hz0.5 W−1, respectively. Finally, the different pressure with 0, 1, 2 kg/cm2 by grown ZnO nanorod, the photo-current to dark-current ratio can achieved 444.59 at 1V. This result may be attributed to internal photoconductive gain mechanism and high-density bridged ZnO nanorods. Our approach provides a simple and controllable method to fabricate high-performance ultraviolet photodetectors.

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Lin, Chao-Chun, and 林兆俊. "High Deep UV Rejection MOS GaN Photodetector with Nano Oxide." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/76387621381916333822.

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碩士
大葉大學
電機工程學系
95
In this thesis, the ultraviolet (UV) GaN-based Metal-Oxide-Semiconductor photodetectors (MOS-PDs)has been fabricated, in which the oxide layer was prepared by using spin nano-particle or liquid-phase-deposition (LPD) oxide. The transparent indium tin oxide (ITO) gate electrode was deposited onto oxide by RF sputtering system having plasma power of 200 W. The Ohmic contact was formed by using Ti/Al alloy metals. A deep ultraviolet of 254 and 366 nm light source was illuminated on the MOS photodetector. It was found that the MOS-PDs with nano-particle oxide exhibited a higher rejection ratio between 254 and 366 nm than that of LPD-oxide by a factor of 277, however compared to the PECVD-oxide by a factor of 349. It was also found that after annealing at 800 ℃ in N2 atmosphere, the low density of interface trap state and oxide trap charge of 9.67×1010 cm-2eV-1 and 6.1×1010 cm-2 were obtained, respectively. According to above results, we successfully used nano-particle oxide to grow silicon oxide layer on GaN-based UV-MOS photodetector. The MOS photodetector has a superior contrast between 366 (UV-A) and 254nm (UV-C) wavelength. Nano-particle oxide MOS-PDs demonstrated responsivities of 130.1mA/W and 5.57mA/W, corresponding to a device quantum efficiency were 44.1% and 2.72% at 366nm and 254nm with a 10V applied bias, respectively.

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14

Lee, Han-Cheng, and 李漢誠. "Growth of Quaternary AlGaInN and Application to UV MIS Photodetector." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/74640266686155678240.

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碩士
國立成功大學
光電科學與工程研究所
95
In the thesis, the epitaxial growth of quaternary AlGaInN film used as the absorption layer of a photodetector was performed using metalorganic chemical vapor dep osition (MOCVD). To our knowledge, the AlGaInN related studies so far have not been widely reported. The one of reasons could be due to the difficulty of controlling the compositions of Al and In in AlGaInN film using MOCVD process. In addition, to correctly estimating the composition ratios of Al and In is another technical hurdle which requires a judicious assessment when dealing with these unique quaternary compounds. First, the PL and X-ray studies were performed in conjunction with use of a formula based on Vegard’s law to estimate composition of Al and In in the AlGaInN. Moreover, XRD simulation was also utilized to double check compositions of Al and In. In addition, relevant studies on determining film surface roughness, depth profiling analysis, and others were performed and discussed. Thin SiO2 layer were also separately deposited on detectors using the PECVD and photo-CVD to compare their effectiveness on reducing the dark current of photodetectors. The resultant UV AlGaInN photodetectors were successfully fabricated and the corresponding detecting wavelength and rejection ratio were determined as 280nm and 32.4, respectively. Lastly, different metal multilayers were also used and compared as contact electrodes for purpose of reducing the dark current of photodetectors.

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15

Chen, Hsuan-Hsu, and 陳炫旭. "Study of the UV MSM photodetector based on AIN thin film." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/70143247371413133071.

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碩士
國立屏東科技大學
機械工程系所
96
In this thesis, we have studied the AlN thin film which is act as the active layer of metal-semiconductor-metal (MSM) structure for the deep UV photodetector. The thesis divided into three parts: (a) Preparation and procedure of AlN thin film；(b) design of interdigital electrode of the photodetector；(c) Measured results of the fabricated UV MSM photodetector. (a) Preparation of AlN thin film In the thesis, we propose a detailed fabricating process and characterization of AlN film UV photodetector. The AlN thin film has 6.2 eV energy gap and high dielectric constant (k=8~10). To deeply study the properties of AlN, we grouped into three main process conditions which are thickness, power, nitrogen/argon concentration ratio variations. To examine the AlN thin film, XRD and Raman measurements is performed for evaluating the crystalline quality. The surface and cross-section of AlN thin film were observed by AFM and SEM. To evaluate the film for actual application qualifications of the deep UV photodetector. (b) Design of interdigital electrode In the second part of the dissertation, we have designed the circular interdigital contact electrodes on fabricated AlN thin film. The currently used MSM photodetectors with rectangular interdigitated contacts have some disadvantages such as increased capacitance, degraded dark current and especially mismatch the integration with optical signal sources. Mo optical sources such as lasers and light emitting diodes (LEDs) have a circular distribution in nature. Therefore, the designed circular contact electrode is commonly used in general photodetector applications. (c) Measured results of the fabricated UV MSM photodetector. In the third part of the dissertation, the characteristics of proposed structure have fast responsivity and the ratio of photo / dark current is more than 5 orders of magnitude (10-5 A - 10-10 A). The ratio of photo / dark current was measurement by I-V system, and appraisal the feasibility that sputter deposition the AlN thin film on Si. Finally, some useful suggestions and future works are made in AlN-based UV MSM photodetector applications.

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16

Deng, Guang-Fu, and 鄧光富. "Effect of different annealing temperature for the ZnO film-UV Photodetector." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/80774938262979050686.

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碩士
國立屏東科技大學
機械工程系所
98
In this thesis, we have researched into the Zinc oxide (ZnO) thin films act as the active layer of metal-semiconductor-metal (MSM) structure for the deep UV photodetector. ZnO is a semiconductor with a the wide energy band gap, which has a high exciton binding energy(60 meV) at room temperature. Therefore, ZnO is a superior choice to be applied to the ultraviolet photodetector device. The thesis is divided into two parts: (a) Fabrication, annealing treatment by high temperature furnace, and analysis of ZnO thin films; (b) preparation and analysis of ultraviolet photodetector device. Part I : (a) Fabrication, annealing treatment, and analysis of ZnO thin films. In this experiment, the ZnO thin films were either deposited on p-type silicon wafer or quartz glass by RF sputtering system at room temperature. The target was a pure zinc material and the power was a variable parameter. Then, in order to discuss the effect on the annealing treatment, the ZnO thin films were annealed in a temperature region from 300 to 700 ℃. Additionally, in order to improve the optical and electrical properties of thin films, the ZnO thin films were annealed at the atmosphere of nitrogen simultaneously. For the physical property analysis of the ZnO thin films, the crystallinity and crystal size of the ZnO thin films which had been annealed with different temperature were measured by x-ray diffraction (XRD); the microstructure and roughness of that were measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. For the optical property analysis of the ZnO thin films, the transmittance and the energy band gap of the ZnO thin films which had been annealed with different temperature were measured by the ultraviolet-visible spectrophotometer (UV-VIS). For the electrical property analysis of the ZnO thin films, the carrier concentration and the carrier mobility were measured by hall effect measurement system . In the experiment results, the ZnO thin films annealed with the different temperature result in the ZnO thin films growing along a orientation of the c-axes. Additionally, the crystal size of ZnO thin films increases as the annealing temperature increases. The SEM and AFM analysis present the variation of the surface microstructure is as a function of annealing temperature. In the transmittance part, the ZnO thin films annealed with different temperature is over 90 % of average transmittance in the visible part of the spectra (380~780 nm). The carrier concentration is also changed with a variation of the annealing temperature. Due to the above results, the appropriate annealing temperature can enhance the crystal structure, optics and electricity properties of ZnO thin films. Part II : (b) Preparation and analysis of ultraviolet photodetector device. The ZnO thin films which had been annealed with different temperature are prepared to ultraviolet photodetector device via a standard process of the exposure, developing, and deposition. The material of the aluminum sputtered on the ZnO thin films is act as a contact electrode for the ZnO metal-semiconductor-metal (MSM) photodetector device. The photocurrent and dark current are measured by semiconductor parameter analyzer. The optimum photodetector sample is that the ZnO thin film is prepared with a deposition power of the 150 W and annealed at 300 ℃. The best ratio of the photocurrent and the dark current was 4.2 when the voltage is 10 V.

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MASFUFIAH, ILMIATUL, and ILMIATUL MASFUFIAH. "Enhanced Photoresponse of UV Photodetector Based on Ni/CNT-Doped ZnO Nanorods." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/20796481404199924521.

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碩士
國立臺灣科技大學
光電工程研究所
105
This study presents the photodetector prepared by using Ni-doped ZnO, CNTDoped ZnO, and Ni/CNT-Doped ZnO, which was grown on glass substrate with seed layer coating as the pretreatment and hydrothermal method. The ZnO nanorods were grown with different concentration of doping. The surface analysis were done by FESEM and EDS shows the increase of concentration linier with the increase of diameter of nanorods, respectively. The combination of Ni/CNT-doped exhibit the highest switch ratio of 4046.51. Additionally, the presented photodetector not only reveals high switch ratio but also demonstrates a stable output responses. It also exhibits good responsitivity as well as quantum efficiency, altogether revealing full potential to be used for practical applications.

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18

Chen, Ming-Hung, and 陳明鴻. "Application of Indium-Tin-Oxide with Improved Transmittance for UV MSM Photodetector." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/68436145649902551569.

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19

Nasiri, Varg Noushin. "Nanoarchitectonics of Ultraporous Nanoparticle Networks for High Performance UV Photodetectors." Phd thesis, 2017. http://hdl.handle.net/1885/118193.

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Accurate detection of ultraviolet radiation is critical to many technologies including wearable devices for skin cancer prevention, optical communication systems and missile launch detection. Si-based photodetectors, relying on n-p type semiconductor homojunction technology, are the most established commercial solution for measurement of ultraviolet light. These devices have some significant shortcomings including high operation voltage, the requirement of longpass filters to block low energy photons and cooling systems to reduce noise and leakage current. This significantly hinders their integration in wearable technologies and alternative solutions are intensively sought. Here, we report a hierarchical design and a rapid synthesis approach for the fabrication of highly performing visible-blind photodetectors based on wide bandgap semiconductors. Combined nano- and micro-scale fine-tuning of the film optical and electrical properties results in record-high photo-currents (milliampere) while preserving pico-ampere dark-currents and excellent selectivity to ultra-low ultraviolet (UV) light densities. In addition, we show that structural engineering of the nanoparticle grain boundaries can drastically enhance the performance of ultraporous nanoparticle network (UNN) photodetectors leading to gigantic photo to dark current ratios with low operation voltages (< 1 V). This is attributed to the optimal interplay of surface depletion and carrier conduction resulting in the formation of an open-neck grain boundary morphology. This is a significant improvement over state-of-the-art devices where a compromise is necessary between high photo-current and low dark-currents. As a result, these photodetectors do not require bulky and costly read-out circuitry and can be directly integrated in portable Complementary metal–oxide–semiconductor (CMOS) based electronics that is currently utilized in many wearable devices. Furthermore, we present a highly performing nanoscale architecture for band-selective UV-photodetectors that features unique tunability and miniaturization potential. The device layout relies on the three dimensional (3D) integration of ultraporous layers of tailored nanoparticles. By tailoring the transmittance window between the indirect band gap of titanium dioxide (TiO2) nanoparticles and the sharp edge of the direct band gap of zinc oxide (ZnO), we achieve a band-selective photoresponse with tunable bandwidth to less than 30 nm. However, a standing challenge with wide bandgap photodetectors is to drastically improve the sluggish response time of these nanostructured devices. In this research, we also present a three-dimensional nanoscale heterojunction architecture for fast-responsive visible-blind UV photodetectors. The device layout consists of p-type nickel oxide (NiO) clusters densely packed on the surface of an ultraporous network of electron-depleted n-type ZnO nanoparticles featuring a significant decrease in the rise and decay times compared to the pure ZnO device. These drastic enhancements in photoresponse dynamics are attributed to the stronger surface band bending and improved electron-hole separation of the nanoscale NiO/ZnO interface. These findings demonstrate a superior architecture for the engineering of miniaturized wearable UV-photodetectors with largely suppressed dark-currents, fast photo-current dynamics and ultra-low power consumption.

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Wang, Chen Tao, and 王振道. "Studying the Fabrication and Photoelectric Characteristics of the TiO2 Composite Graphene UV Photodetector." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/zrkh83.

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碩士
國立中正大學
光機電整合工程研究所
102
In this article we prepare the graphene photodetector in three steps. First, we deposited aluminum on the copper foil by thermal evaporation, second, growing graphene on a copper foil by CVD method, third, it is transferred onto the Si substrate to manufacture graphene photodetector, and in order to increase the absorption of UV light, we us droplet (Drop coating) to deposite titanium dioxide on graphene photodetectors formed graphene composite photodetector, which aims to explore the different titanium oxide layers to effect titanium dioxide - graphene composite photodectector optical characteristics of photoelectric detectors. 　From the experimental results, the responsivity, rising time and falling time, on-off ratio of the graphene photodetector is measured respectively in the 365 nm LED light：1.03 A / W, 0.051 s, 0.115 s, Ion / Ioff = 1.47 ; while depositing a second layer of titanium dioxide has the best optical features: responsivity, rising time and falling time, on-off ratio, respectively: 2.68 A / W, 0.04 s, 0.048 s, Ion / Ioff = 3.55 ; the reason is presumably because the ultraviolet light irradiation of the oxide semiconductor nanoparticles adsorbed desorption of oxygen molecules on the surface, so that the current component through rising, therefore the optical features is increase by the above reason.

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21

Ching-ChienHsu and 許景鈐. "Metal Oxide Semiconductor with Wide Bandgap Applied on Deep UV Solar Blind Photodetector." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/t2yn8g.

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碩士
國立成功大學
微電子工程研究所
105
In the thesis, two metal oxide semiconductor with wide bandgap, IGO and MgInO, were applied on the fabrication of deep UV solar-blind photodetector. The thesis is classified into two part. In the first part of the experiment, the MSM structured UV photodetector based on In2O3 doped Ga2O3 (IGO) was fabricated with different concentration of oxygen flow treatment during sputtering process. In the second part, the semiconductor with wider bandgap MgO replaced Ga2O3 to form a deeper wavelength of UV detector. In the first part, the IGO film was deposited on glass substrate by co-sputtering using In2O3 and Ga2O3 targets with different percentage of oxygen flow from 0% to 8%. The oxygen vacancy defects were improved with the increase of oxygen concentration during sputtering. With oxygen flow involved during sputtering process, the dark current of the device was effectively suppressed and the photo/dark current ratio was enhanced. Sample C with 4% of oxygen concentration has the best performance of photo/dark current ratio more than five orders, UV-to-visible rejection ratio of 1.1×105 and two decay time constants of 0.02/0.75 second among five samples. In the second part, MgInO photodetectors were fabricated with different concentration of 2%, 4%, 6% of oxygen flow treatment during sputtering process. As the oxygen flow rate increased, the deposited MgInO film during sputtering was fully oxidized, leading to a high transmittance and a high quality of transparency. The energy bandgap of MgInO thin film increased obviously with the increase of oxygen concentration during sputtering. Under an applied bias of 2 V, sample A has the best performance of NEP for having the minimum value of 2.03×10-12 and the maximum value of 7.38×1012 cm Hz0.5W-1 of Detectivity. Sample C with 6% of oxygen concentration has the best performance of UV-to-visible rejection ratio of 5.95×104 and two decay time constants of 1.91/13.17 second among three samples.

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22

Tsai, En-Feng, and 蔡恩鳳. "Fabrication of Zinc and Oxygen Terminal Surface ZnO Nanorods for UV Photodetector Application." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/xhebqy.

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碩士
國立臺北科技大學
製造科技研究所
106
In this study, polar and nonpolar ZnO thin films were used to be a buffer layer to synthesize one dimensional polar O terminal surface and Zn terminal surface ZnO nanorods and nonpolar ZnO nanorods for UV photodetector sensing layer. First, polar and nonpolar ZnO thin films were deposited onto p-type (100) Si substrate using Plasma Enhanced Chemical Vapor Deposition system(PECVD). Second, the two different as-prepared thin films used to synthesize the polar zinc and oxygen terminal surface and nonpolar ZnO nanorods by a simple hydrothermal method. In this part, we investigated the influence of different mole concentration of the aqueous solution. As the result, we successfully synthesized the vertical polar ZnO nanorods at T = 100℃, C = 0.05 Mole in 40 min zinc and oxygen terminal surface and horizontal nonpolar ZnO nanorods at T = 80℃, C = 0.05 Mole in 1 h. After finished one dimensional polar O terminal surface and Zn terminal surface ZnO nanorods and nonpolar ZnO nanorods, we used silver as top electrodes to fabricate horizontal structures of metal-semiconductor-metal (MSM) with Schottky contact behavior. The colloidal silver was directly coated onto the sample. As the result, the performance of ZnO-based photodetector silver electrodes, it is showing the good reproducibility and stability after 5 times switching of UV illumination. Moreover, the sensitivity was enhanced after synthesized the nanorods structure on the polar or nonpolar ZnO buffer layer. For ZnO-based photodetector with polar zinc and oxygen terminal surface nanorods structure, the polar ZnO thin films photo gain increased from 5.73 to 22.48 by growth O terminal surface one dimensional ZnO nanorods and 55.73 by growth Zn terminal surface one dimensional ZnO nanorods. And polar ZnO thin films responsivity (mA/W) increase from 3.18 (mA/W) to 10.59 (mA/W) by growth O terminal surface one dimensional ZnO nanorods and 71.60 (mA/W) by growth Zn terminal surface one dimensional ZnO nanorods. On the other hand, in the case of the ZnO-based photodetector with nonpolar nanorod structure, the photo gain decreased from 25.93 to 8.64 and the responsivity (mA/W) decreased from 0.238 to 0.082. According to the results, the polar zinc and oxygen terminal surface nanorods photodetector exhibit a good photo gain and responsivity. In contrast, nonpolar nanorods performance decrease because of nanorods size effect the UV photodetector.

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23

SONG, WAN-JHEN, and 宋宛臻. "Sputtering ZnO and TiN into silicone oil and their application to UV photodetector." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/z35anc.

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碩士
國立臺灣科技大學
材料科學與工程系
104
Zinc oxide and titanium nitride nanoparticles were prepared on silicone oil by RF magnetron sputtering and they were characterized. The samples were prepared by three different methods. Firstly, it was sputtered directly onto the substrate without silicon oil, secondly, silicone oil was evaporate using a hot plate to condense on the substrate and then sputtered onto it and thirdly, they were sputtered on petri dish which contains 3 ml of silicone oil. TEM analysis confirmed the polycrystalline structure of the nanoparticles and the particle sizes of as-produced zinc oxide and titanium nitride were about 5.7±0.6 nm and 6.3±1.5 nm respectively. The samples which contain evaporated silicone oil was found to be wrinkle structured while samples which were prepared without silicone oil were different in structure. In addition, UV photodetectors were fabricated by depositing ZnO nanoparticles and TiN nanoparticles which is deposited onto Ag Interdigitated electrodes. The current-voltage (I-V) curves were measured using dark and UV light conditions. The response time (I-T) of the devices were measured to investigate the relationship between photoconductive performance and the characteristics which were affected by silicone oil. The experimental results show that the photodetectors with nanoparticles which were prepared on silicone oil have high responsivity than the nanoparticles without silicone oil.

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24

Chang, Chu-Fung, and 張褚峰. "Fabrication of highly oriented c-axis AlN films and their application for UV photodetector." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/z2c4nv.

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碩士
國立臺北科技大學
機電整合研究所
98
Future missions for space astronomy, defense, science and technology required UV photodetector that possess high sensitivity, high precision, low power loss, and high thermal stability. Recently, aluminum nitride has attracted a worldwide attention for potential applications in UV photodetectors, as it possesses good photoconductive properties, including of wide bandgap (~ 6.2 eV), high thermal conductivity as well as high chemical stability. In this study, to develop the applications metal - semiconductor – metal photodetectors, AlN thin films were deposited onto Si (100) and Sapphire (001) substrate by using unbalanced magnetron sputtering system. Effects of various parameters on properties of coated AlN were investigated to obtain the c-axis AlN films. The obtained AlN thin films were employed to fabricate the Inter Digital Transducer (IDT) by using lithography and lift-off methods. To achieve an Ohmic contact as a conduction current interface for UV detector, the films finally were annealed at 500 oC in argon atmosphere (20 sccm of flow rate), with working pressure of 2x10-2 torr for 10 min. The produced films were characterized by X-ray diffractometry, scanning electron microscopy (SEM), atomic force microscopy (AFM). From X-ray diffraction, nitrogen concentration and RF power have the most significant impact to the deposition of high C-axis AlN films. High C-axis AlN thin films were successfully deposited onto Si (100) substrate with 0.2007o of FWHM and 458.8 nm of thickness, as the RF power was 175 w, 50% of nitrogen concentration, 4 mTorr of working pressure and 3 hours process. The AFM results showed that the roughness were < 5 nm (Rms). The AlN films finally were employed to fabricate UV photodetector. From photoconductivity measurement, as the applied bias voltage was ±10V, the self-detector for UV light irradiation (250-400 nm) has a current gain increases about 3 orders.

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25

Huang, Guo-Jhih, and 黃國智. "Optoelectric Characteristics Studies and Synthesize of Layer By Layer TiO2/Graphene Composite UV Photodetector." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/bcrej3.

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碩士
國立中正大學
光機電整合工程研究所
103
In this study, TiO2/graphene composite photodetector was synthesized by four steps which involved firstly graphene was grown on polished copper foil by chemical vapor deposition (CVD) technique, followed by transferring the graphene onto glass substrate. The third step was to increase the UV absorption by drop cast TiO¬2 on graphene and finally, second step and third steps were repeated to increase the number of layer-by-layer of TiO2/graphene. The effect and optoelectronic characteristic of different TiO2/graphene layers composite photodetector were studied. The responsivity and on-off ratio of the synthesized devices were measured under 365 nm Light Emitting Diode (LED) light irradiation. The responsivity of the device was found as -2.454 A/W, whereas the on-off ratio was measured as –9.9%. The best device was found to be the 4-layer stacking layer-by-later TiO2/graphene which has the best responsivity, rising time and falling time, and on-off ratio with the value of 179.53 A/W, 5.94 s, 45.98 s, and Iphoto/Idark = 23.7%, respectively. The reasons may due to the excitation of photo electron-hole pairs caused by ultraviolet light irradiation and were collected efficiently by graphene. Besides, the photocurrent and optical properties were greatly enhanced due to absence of oxygen on the surface of graphene.

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26

SUN, PEI-JYUN, and 孫培鈞. "The Investigation of The GaN Metal-Semiconductor-Metal Near UV Photodetector with Trench Structure." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/mvauav.

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碩士
南臺科技大學
電子工程系
106
In this study, the normal metal-semiconductor-metal (MSM) GaN photodetector, named PD1, was fabricated, and its characteristics of I-V, response, and low frequency noise were also measured. Then, two types of MSM photodetectors with trench structures were fabricated by using the ICP-RIE etching process. The first one, named PD2, is fabricated with the electrode on the upper side of the trench, and the second one, named PD3, is fabricated with the electrode on the lower side. From the I-V curve characteristics, it can be shown that the photo current and dark current of PD2 and PD3 are higher than those of PD1 due to the surface defects generated by etching process. On the other hand, it was also found that the photo current and dark current of PDs with trench structures are depending on the position of the electrode. The mechanism is verified by the low-temperature I-V measurements. PD3 has the highest photo current, but the highest dark current of PD3 causes the worst ratio of photo to dark current, which is also reflected in the response measurement. It can be thought that the highest responsivity of PD3 with internal gain generated by the defects, but at the same time the defects also lead to the worst ultraviolet/visible rejection ratios. It's a fatal flaw for photodetectors. Therefore, it can't be proved that the responses of PDs are enhanced by using trench structure. In order to improve the dark current, the rapid thermal annealing (RTA) process was performed after the etching process. It can be noted that the dark currents of PD2 and PD3 can be effectively reduced, but the responsivities of these two devices are also decreased without the effect of internal gain. This is attributed to the reduction of the defects lead to the transmission paths by tunneling mechanism. After RAT process, the responsivities of PD2 and PD3 are still higher than PD1. Therefore, it can be proved that the responses of PDs are enhanced by using trench structure. And, the ultraviolet/visible rejection ratios are also improved after RTA. Finally, in the analysis of low frequency noise, the noise power densities of PD2 and PD3 with RTA process can be improved due to the reduction of dark current. And, the detectivities (D*) of PD2 and PD3 are better that that of PD1.

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27

Wu, Ya-Hsuan, and 吳亞軒. "Hybrid ZnO Nanoparticles/Graphene/P3HT UV-Visible Photodetector with High Responsivity and Dual Photocurrent Responses." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/18531829516184972186.

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碩士
國立臺灣大學
物理學研究所
105
Traditional dual-band, multi-band or multi-color photodetectors are fabricated by stacking two or more light-absorbing materials, which utilize the mechanism of inter-band/inter-band transition for light detection and signal generation, however, the process of fabrication is complex, and the photoresponse is low. In this study, we proposed a new device composed of a graphene layer synthesized by chemical vapor deposition (CVD) process between ZnO nanoparticles (ZnO NPs) and the poly (3-hexylthiophene) P3HT layer. By using such a three-layered heterojunction combined with the excellent conductivity of graphene and high absorption of semiconductor quantum dots and P3HT, we successfully achieved a photodetector with high sensitivity and dual photoresponses. In addition, this unique structure enables the detector not only to detect a wide spectral range spanning from ultraviolet to visible, but also exhibits dual photoresponses, the visible (> 400 nm) in which a positive photocurrent is obtained, while in the ultraviolet (< 400 nm) a negative photocurrent is measured. The underlying mechanism responsible for these intriguing behaviors has been developed based upon the band alignment of the heterostructure. Besides, due to the flexibility of all the constituents, the device possesses flexible characteristics, which is very useful for the development of the future integrated wearable systems.

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28

Chen, Mao-Yi, and 陳懋億. "Fabrication of highly c-axis oriented ZnO thin films for UV photodetector applications by PECVD." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/nrdxfr.

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碩士
國立臺北科技大學
製造科技研究所
101
The goal of this study are two folds. First, high c-axis ZnO thin films were deposited onto p-Si (100) substrates using Plasma Enhanced Chemical Vapour Deposition system. It was found that the CO2 concentration have significant effects on the quality of the ZnO thin films. Also, high c-axis ZnO film with outstanding properties was successfully prepared under 70 W of radio frequency power, CO2:DEZn = 3:1, 6 Torr of working pressure, 5 minutes of deposition time, and 400 oC of deposition temperature. Second, the as-prepared ZnO thin films were employed to fabricate horizontal structures of metal – semiconductor – metal (MSM) with Ohmic contact behavior. The interdigital Pt electrodes having thickness of 100 nm were deposited onto the ZnO films using sputtering and lithography techniques. In order to improve the sensitivity as well as reduce the loss-efficiency of the Pt electrodes and the ZnO films, the rapid thermal annealing procedures were carried out in Ar, N2, and vacuum ambient under 5 Torr of pressure, 150 oC to 550 oC of temperature, and 5 to 20 minutes of annealing time. The results showed that the Ohmic contact was obtained in Ar ambient at 450 oC for 10 minutes. From electrical investigations, the dark and photo currents were 5 mA and 30 mA, respectively. This revealed that the fabricated device possessed highly response to UV irradiation with exponential function. Also, the results showed that the measured currents increased by 80% after 6.26 seconds of irradiation and quickly reduced to originated condition. The results in this study indeed demonstrated the potential application of ZnO thin films in UV detectos.

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Yong-Hua, En, and 雍華恩. "Studying the Fabrication and Photoelectric Characteristics of the CsWO3 Drop Casting on Graphene UV Photodetector." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/363ggh.

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碩士
國立中正大學
光機電整合工程研究所
102
In this research, we are synthesize the nano-sized homogenous CsxWO3 particles by using hydrothermal method, and then drop casting CsxWO3 solution on the Si substrate, which has transferred graphene on it. We try to observe that the effect of optical characteristics in UV irradiation with different number of CsxWO3 layers. The result revealed that the thin film of CsxWO3 has excellent absorbance in ultraviolet light, (hole-trapping chemisorbed oxygen molecules at the surface of photosensitive materials in which the UV light induced desorption/re-absorption of oxygen molecules occurs, resulting in the increase/reduction of the photocurrent.) According to the result, we found that having the three layers of drop casting has the best performance: responsivity = 1267.52 A/W, rising time = 4.91 s, falling time = 8.24 s, Ion/ Ioff = 1.62, It confirms the truth of using graphene as a base can improve responsivity and response time.

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30

Lin, Wei-Jhih, and 林煒智. "Fabrication of highly c-axis oriented ZnO thin films for UV photodetector applications by PECVD." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/uzvd5q.

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碩士
國立臺北科技大學
製造科技研究所
102
In the study, metallic zinc thin films were deposited onto c-cut sapphire substrates by plasma enhanced chemical vapor deposition system (PECVD) with Diethylzinc (DEZn) as precursors, after atmosphere annealing at 450 ℃and 550 ℃, metallic zinc thin films will transfer to zinc oxide phase with nanostructure such as nanorods or nanowires, and radio-frequency (RF) magnetron sputtering was used to deposit Pt top electrode onto the ZnO nanorods and nanowires. The as-deposited Pt/ZnO nanocomposite samples were then annealed at 450 ℃ in argon ambiences to obtain optimal Ohmic contacts by RTA which can prevent the efficiency loss of Pt electrodes and ZnO nanorods or nanowires. The crystal structure, surface morphology, optical properties, and wettability of ZnO nanorods and nanowires were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), photoluminescence (PL), and water contact angle meter, respectively. Moreover, the photoconductivity of the Pt/ZnO nanocomposite was also investigated for UV photodetector application. According to the result of analysis, highly c-axis prefer orientation Zn whisker-like structure were successfully deposited by PECVD, ZnO nanorods and nanowires can be obtained during the annealing process. All the samples exhibit highly photoresponse which I-V characteristics showed the photo current to dark current contrast could almost reach 1.8 order of magnitude. As a result, the ZnO photodetector with coral-like nanostructure showed good ohmic contacts behavior and stable UV photo responsibility after 5 times switching on and off UV illumination for 120s. Also, the ZnO photodetector exhibit super-hydrophobic behavior due to self-assemble nanostructure. However, waterproof UV detectors were successfully fabricated in this research work, and it has deeply potential for ZnO multifunctional devices applications.

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31

Chao, Chung-Hua, and 趙崇華. "Synthesis of Polar and Nonpolar ZnO Thin Films on Silicon Substrates for UV Photodetector Application." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/j728p5.

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博士
國立臺北科技大學
機電學院機電科技博士班
104
ZnO is a promising semiconductor material for many kinds of functional optoelectronics applications due to its wide direct band gap of 3.37 eV and high exciton binding energy of 60 meV at room temperature. ZnO is a hexagonal wurtzite structure and exhibits a non-centrosymmetric structure, which causes that the ZnO possesses polar and nonpolar plane. The polar and nonpolar planes show the different surface atomic configurations and physic and chemistry properties anisotropic, making that the ZnO attracts extensive research interests and diversity applications. The polar plane for ZnO is (0002) plane, which is a lowest surface energy plane. The most of studies are focus on growth of polar c-orientation ZnO nanostructures and explore its material properties and relative applications. Compared with polar ZnO, the nonpolar planes of (101 ̅0) and (112 ̅0) ZnO are seldom reported due to the difficulty of preparation. However, nonpolar ZnO is considered as a candidate material for next generation high efficiency optoelectronic device due to absence of spontaneous polarization effect in the crystal. Therefore, this present study used plasma enhanced chemical vapor deposition (PECVD) system to synthesize polar and nonpolar ZnO thin films. By adjusting the synthesis temperature, synthesis pressure, and precursor gas flow rate ratio to obtain the high quality ZnO thin films are the first step in this study. The experimental results indicate that the synthesis temperature is a dominated process parameter for controlling the crystallographic orientation of ZnO, and the crystal quality can be improved by altering the synthesis pressure and precursor gas flow rate ratio. Moreover, the possible growth mechanism of ZnO with different crystallographic orientations have been proposed based on the OES analyses and SEM observations. Both the polar and nonpolar ZnO thin films are used as a sensing layer for UV photodetectors applications. The interdigitated Pt thin films were deposited onto the polar and nonpolar ZnO thin films as a contact electrodes via conventional lithography process and RF sputtering. The performance including responsivity, reliability, and sensitivity of both detector were determined by typical current-voltage (I-V) characterization under dark and UV light illumination and time-dependent photoresponse measurement. The photoresponse results indicated that the nonpolar detector possesses better responsivity (4708.88 μA/W) and faster response (0.141 s) and recovery times (0.125 s) than the polar one (3367.73 μA/W, the response time cannot be determined). The performance of the polar ZnO-based UV photodetector can be improved by using RTA system annealed in different ambients. The photodetector annealed in air revealed the largest responsivity at operating temperature of 25 oC while the detector annealed in nitrogen showed a stable responsivity. The nonpolar ZnO-based UV photodetector with Pt as a contact electrode natively possesses good sensitivity and acceptable responsivity and reliability, but the polar ZnO-based UV photodetector have to be improved through a post-annealing assistance to exhibit a good performance.

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Liang, Chin Min, and 梁晉銘. "Research of Sidewall Passivation for 450nm LED and Application of Metal- semiconductor-metal UV Photodetector." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/26006932269361048376.

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碩士
國立清華大學
電子工程研究所
104
The thesis is divided into two parts. First, we investigate the fabrication and characterization of different mesa structure and observe the trend of leakage whether it is dominated by the perimeter or not for LEDs. Moreover, we change the finger number of interdigitated LEDs to proof that the leakage increases exponentially again. On the other hand, we would like to observe if ICP do different damages to different finger spacing of interdigitated LEDs and leads to different trend of leakage. In the end, we use different passivation such as Al2O3 by ALD, SiO2 and SiN by PECVD to improve the leakage. Second, we attempt to apply the above research results on the metal- semiconductor-metal (MSM) photodetector by asymmetric electrode structures. As far as known, the surface leakage is the dominant mechanism for dark current for MSM PDs. With the higher density of trap states on the surface, the higher leakage current is obtained. Therefore, we would like to reduce the leakage current by depositing passivation layer, which is based on the previous research. Moreover, we also induce the theorem of Anti-reflection (AR) coating. We hope that the passivation can reduce the leakage current without blocking the light. On the other hand, we also change the finger spacing of MSM PDs to see what their difference in characteristics is.

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33

Huang, Guang-Wei, and 黃光緯. "The UV/VIS Photodetector Fabrication and Photo Characteristics Study of Deposited Sb2S3 on TiO2-Graphene Composite." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/erkp7d.

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碩士
國立中正大學
光機電整合工程研究所
103
In this study, graphene was grown on copper foil by chemical vapour deposition (CVD) and transferred onto glass substrate. Then, TiO2 and Sb2S3 semiconductor thin film were deposited onto graphene by drop casting and chemical bath deposition (CBD) respectively. The responsivity of graphene on UV light and visible light was increased with this enhancement. The effect of different casted TiO2 layers on the responsivity of the device was studied. The optimized device was defined. The most suitable responsive wavelength and responsivity of the device were measured by full-spectrum technique. The best responsivity and time response of the optimized device were determined by Xenon (Xe) lamp, Light Emitting Diode (LED) and Laser. Irradiated light with 405 nm and 1 μW by Xe lamp showed best responsivity which is 560 A/W, whereas 405 nm and 45 mW of Laser beam showed shortest rising and falling time which are 0.74 s and 37 s respectively. The deposition of TiO2 and Sb2S3 semiconductor on graphene photodetector was proven increasing the responsivity of the device and successfully fabricated.

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34

Chiou, Jung-Ran, and 邱榮仁. "The Characteristics of GaN MIS Capacitor Using Photo-CVD SiO2 and Its Application in UV Photodetector." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/73589920330926125647.

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碩士
國立雲林科技大學
電子與資訊工程研究所碩士班
90
For the formation of high-quality SiO2 Films using direct photo chemical vapor deposition (DPCVD) on the various semiconductor substrates has been proposed and investigated in this thesis. It was established that good and reliable properties of SiO2 and SiO2/semiconductor interface could be obtained from this process. In order to obtain this issue, we will propose an easy and vapor phase oxidation method in this study. Since the photo chemical vapor native oxidation is a dry oxidation method deposited at a high temperature and thus obtain a high quality interface. SiO2 insulating layers were deposited onto GaN by photo chemical vapor deposition (photo-CVD) technology using deuterium (D2) lamp as the excitation source. Physical, chemical and electrical characteristics of the Al/SiO2/GaN metal-insulator-semiconductor (MIS) capacitors were investigated by AFM, AES, XRD, I-V and C-V. It was found that the as-deposited photo-CVD SiO2 films were poly-crystalline. It was also found that the limiting factor of SiO2 growth rate was the amount of SiH4 and O2 molecules available to provide excited Si and O atoms. Furthermore, it was found that the SiO2/GaN interface trap density, Dit, equals to 8.4´1011cm-2eV-1 for the photo-CVD SiO2 layers prepared at 300oC. With an applied field of 4MV/cm, the oxide leakage current density was found to be only 6.6´10-7A/cm2. The Sputter-ITO, TiN and E-Gun ITO films deposited onto GaN as the transparent electrodes in the application of metal-semiconductor-metal photodetectors were first fabricated and reported. The transmittance of Sputter-ITO, TiN and E-Gun ITO films for thickness of 1000Å was 94%, 62% and 85% respectively at wavelength of 400nm. Unlike TiN films, the variation of transmittance of sputter ITO films was not sensitive to the thickness. Also the effective barrier height of Sputter-ITO, TiN and E-Gun ITO films to GaN was 0.46, 0.59 and 0.95 eV respectively. The photo/dark contrast of sputter-ITO, TiN and E-Gun ITO MSM photodetectors was 0.36, 3 and 4.25 orders at 5V bias respectively. Finally we found the maximum photo/dark contrast of GaN MIS photodetectors was about 3 orders at 5V bias under D2 lamp illuminated.

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35

CAI, MING-ZHANG, and 蔡明彰. "Preparation and characterization of a-Si: H/a-SiC:H heterojunction UV enhanced and blue light photodetector." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/35035542170438813386.

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36

CHEN, HONG-RUI, and 陳虹瑞. "Improved Fabrication Process for UV/VIS Photodetector and Photo Characteristics Study of Deposited Sb2S3 on TiO2-Graphene Composite Material by Chemical Bath Deposition." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/2yaevc.

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碩士
國立中正大學
光機電整合工程研究所
105
In this study, TiO2 semiconductor thin film were deposited onto glass substrate by drop casting . Then graphene was grown on copper foil by chemical vapor deposition (CVD) and transferred onto TiO2 semiconductor thin film. Finally, Sb2S3 semiconductor thin film were deposited onto graphene by chemical bath deposition (CBD) respectively. The responsivity of graphene on UV light and visible light was increased with this enhancement. The effect of different casted TiO2 layers on the responsivity of the device was studied. The optimized device was defined. The most suitable responsive wavelength and responsivity of the device were measured by full-spectrum technique. The best responsivity and time response of the optimized device were determined by Xenon (Xe) lamp, Light Emitting Diode (LED) and Laser. Irradiated light with 365 nm and 1 μW by Xe lamp showed best responsivity which is 732 A/W, whereas 365 nm and 50 mW of LED light showed shortest rising and falling time which are 0.16 s and 0.59 s respectively. And Irradiated light with 405 nm and 1 μW by Xe lamp showed best responsivity which is 14.33 A/W, 405 nm and 50 mW of LED light showed shortest rising and falling time which are 3 ms and 25 ms respectively. The deposition of TiO2 and Sb2S3 semiconductor on graphene photodetector was proven increasing the responsivity of the device and successfully fabricated Keywords : graphene, Sol-gel method, Chemical bath deposition, TiO2, Sb2S3, Photodetector, Multiple-unit semiconductor device

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37

Guan-JieHuang and 黃冠傑. "β-Ga2O3 UV photodetectors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/25762851220644262022.

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38

Chang, Jing-Fa, and 張敬法. "MgZnO-Based UV photodetectors." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34370777660456888613.

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碩士
崑山科技大學
光電工程研究所
102
In this paper, the MgZnO thin film were deposited on quartz substrate by RF-sputtering system. The ambient controlling were divided to the flow rate of oxygen and the annealing temperature, compare the film characteristic and found the better condition to deposit the device with different thickness. In this research, the atomic force microscopy (AFM), X-ray diffraction (XRD) and uv-vis spectrophotometer were used to analyze the film crystallization as well as the optical characteristics. The electrical characteristics were measured by the B1500A Semiconductor Device Parameter Analyzer. The measurement results shows that under the flow rate of 40:10 and the thickness of 100nm, the device performed the best characteristics. First of all, the transmittance of the thin film were higher than 80% in visible region, besides, the responsivity could be achieved to 5.2822E-7 A/W under 5V bias and the rejection ratio was measured to 472. The stability of the device could also be confirmed by the switching test

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39

Wei, Ming. "Growth and Characterization of ZnO Based Semiconductor Materials and Devices." Doctoral diss., 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6202.

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Wide band gap semiconductors such as MgxZn1-xO represent an excellent choice for making optical photodetectors and emitters operating in the UV spectral region. High crystal and optical quality MgxZn1-xO thin films were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy. ZnO thin films with high crystalline quality, low defect and dislocation densities, and sub-nanometer surface roughness were achieved by applying a low temperature nucleation layer. The critical growth conditions were discussed to obtain a high quality film: the sequence of Zn and O sources for initial growth of nucleation layer, growth temperatures for both ZnO nucleation and growth layers, and Zn/O ratio. By tuning Mg/Zn flux ratio, wurtzite MgxZn1-xO thin films with Mg composition as high as x=0.46 were obtained without phase segregation. The steep optical absorption edges were shown with a cut-off wavelength as short as 278nm, indicating of suitability of such material for solar blind photo detectors. Consequently, Metal-Semiconductor-Metal photoconductive and Schottky barrier devices with interdigital electrode geometry and active surface area of 1 mm2 were fabricated and characterized. Photoconductor based on showed ~100 A/W peak responsivity at wavelength of ~260nm. ZnO homoepitaxial growth was also demonstrated which has the potential to achieve very low dislocation densities and high efficiency LEDs. Two types of Zn-polar ZnO substrates were chosen in this study: one with 0.5° miscut angle toward the [1-100] direction and the other without any miscut angle. We have demonstrated high quality films on both substrates with a low growth temperature (610°C) compared to most of other reported work on homoepitaxial growth. An atomically flat surface with one or two monolayer step height along the [0001] direction was achieved. By detail discussions about several impact factors for the epitaxial films, ZnO films with high crystallinity verified by XRD in different crystal orientations, high PL lifetime (~0.35 ns), and not obvious threading dislocations were achieved. Due to the difficulty of conventional p-type doping with p dopant, we have explored the possibility of p-type doping with the assistance of other novel method, i.e. polarization induced effect. The idea is the sheet layer of two dimensional hole gases (2DHG) caused by the wurtzite structure's intrinsic polarization effect can be expanded to three dimension hole distribution by growing a MgZnO layer with a Mg concentration gradient. By simulation of LED structure with gradient MgZnO structure, the polarization effect was found not intense as that for III-nitrides because the difference of spontaneous polarization between ZnO and MgO is smaller than that of GaN and AlN, and the piezoelectric polarization effect may even cancel the spontaneous polarization induced effect. We have grown the linear gradient MgZnO structure with Mg composition grading from 0% to 43%, confirmed by SIMS. Hall measurement did not show any p-type conductivity, which further indicates MgZnO's weak polarization doping effect. However, the gradient MgZnO layer could act as an electron blocking layer without blocking holes injected from p layer, which is useful for high efficiency light emitters.
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics and Photonics

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40

Ssu-HaoLiao and 廖思豪. "Characteristic Improvement of GaN-based UV Photodetectors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/53767206186327688085.

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41

Peng, Shi Ming, and 彭士銘. "UV MSM photodetectors with selective growth ZnO nanorods." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/98h5dx.

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碩士
國立虎尾科技大學
光電與材料科技研究所
96
In the study, metal–insulator–semiconductor (MSM) ultraviolet photodetectors with selective growth ZnO nanorods(NRs) were fabricated The ZnO seed layers were prepared on corning glass substrates by radio frequency (rf) sputter. The morphology of ZnO seed layer, pH, growth temperature, and concentration of zinc salt in aqueous solution were important parameters to determine growth characteristics such as average diameters and lengths of ZnO nanorods. In addition, it was found the different nanostructures by adjusting parameter. ZnO seed layers were prepared on glass by three different methods which are spin coating, dip coating and nanopartical-film. Sequentially, well-aligned ZnO nanorod arrays were grown on ZnO seed layers by an aqueous solution. The photoluminescence (PL), X-ray diffraction (XRD), Micro-Raman , Atomic force microscope (AFM) and high-resolution transmission electron microscopy (HRTEM) were then used to characterize the optical and crystallographic properties of the as-grown ZnO NRs. Surface morphologies and size distribution of the NRs were characterized by field-emission scanning electron microscope (FE-SEM). In other study, ZnO nanorods based Metal-semiconductor-metal (MSM) and selective film ultraviolet (UV) photodetectors were fabricated with interdigital (IDT) structure by using Ag Schottky contact electrodes. Room temperature current–voltage (I–V) characteristics of the devices were then measured by an HP 4156C semiconductor parameter analyzer under both darkness and illumination. TRAIX 180 was used as the light source for spectral responsivity measurements. We fabricated three structures of MSM PDs( 40 nm film, 40 nm/NRs, and 40 nm film O2/NRs). First of all, we define UV to visible rejection ratio as the responsivity measured at 360 nm divided by the responsivity measured at 450 nm. It was found that UV-to-visible rejection ratio of the fabricated photodetector were 8.74, 13.82, 28.28 and 336.65, respectively. Sequencely, the responsivities of different MSM photodetectors were measured respectively. It was found that sharp cutoff occurred at around 370 nm while the incident optical power was 4.38 μW/cm2. At 5V applied bias, the responsivity of 7.82×10-6, 0.0015, 0.13, and 41.22 A/W were achieved at 370 nm. Comparing two different structures of MSM PDs(40 nm film and 40 nm film O2/NRs), we found the UV-to-visible rejection ratio of 40nm film O2/NRs MSM PDs is two orders of magnitude larger than 40nm-film-MSM PDs. The 40nm/NRs-2 compared with 40 nm/NRs-1 measured optical responsivities under different optical power(17.1 and 4.38μW/cm2 ), it was found that the condition achieve a UV-to-visible rejection ratio of two orders. With incident light wavelength of 370 nm and 5V applied bias, the measured responsivities were 8.85, and 0.0015 A/W. As a result, the influence of light source intensity is important to optical responsivities. Furthermore, because of the high surface-to-volume ratio, trapping at surface of nanorods drastically affects energy band and produce photoconduction gain in nanorod MSM-PDs. In the dark, Extra energy band produced from surface trap, which oxygen molecules are adsorbed on the surface of nanorods and capture the free electrons[O2(g)+e-?O2-(ad)]. Upon illumination with photo energy large energy bandgap, electron-hole pairs are photogenerated [hυ?e- + h+]. electron-hole pairs are photogenerated and holes are readily trapped at the surface, leaving behind unpaired electrons, which increase the conductivity under desorption oxygen ions [h+ + O2-(ad) ?O2(g)]. However, the unpaired electrons or recombine with holes generated photoconduction gain. Vertically well-aligned ZnO nanorod and selection film UV photodetectors were fabricated on glass substructures.It is useful to develop low cost short wavelength UV photodetectors and has a great potential for the nanodevice application in further study.

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CHEN, JHAO-CHENG, and 陳昭誠. "Flexible CsPbBr3/ZnO Nanocomposites for UV Photodetectors Applications." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/33bdm2.

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碩士
國立臺北科技大學
製造科技研究所
107
In this study, we separate it to three steps, first polar ZnO thin films were used to be a buffer layer for synthesizing the second step’s one dimensional polar ZnO nanorods, then we start using these samples to be the UV photodetectors to discuss the reproducibility and stability of this sample. Lastly, spin coating CsPbBr3 perovskite quantum dots on top for UV photodetector sensing. First, polar ZnO thin films were deposited onto the p-type (100) Si and mica substrate by using Plasma Enhanced Chemical Vapor Deposition (PECVD)system. Second, utilizing the as-prepared thin films from two different substrates to synthesize ZnO nanorods by a simple hydrothermal method. Herein, we discovered the influence of the different growth time. Moreover, we used spin coaters to spin coating CsPbBr3 perovskite on top, and study these nanocomposites by using these samples as UV photodetectors then discuss the responsivity and sensitivity. According to the flexibility of mica substrate, we bend the mica substrate and discuss that with different direction of the force whether the substrate is changed and how. As a result, we successfully synthesized the vertical polar ZnO nanorods. After finishing one dimensional polar ZnO nanorods, we spin coating CsPbBr3 ¬perovskite ontop and identify these samples. After finish these nanocomposites we used platinum as top electrodes to fabricate horizontal structures of metal-semiconductor-metal (MSM) with Schottky contact behavior. As a result, the performance of ZnO-based photodetector platinum electrodes, it is showing the good reproducibility and stability after 5 times switching of UV illumination. Moreover, the sensitivity was enhanced after synthesized the nanorods structure on the polar ZnO buffer layer. For ZnO-based photodetector, the polar ZnO thin films photo gain increased by growth ZnO nanorods with 1hr growth time. What’s more, after spin coating perovskite we make the photo gain become larger and both the responsivity, to find out the self-powered ability we give 0V and still get the response. Lastly, we compare the force from the opposite direction to bend the mica substrate and found out with tensile force show good reproducibility and stability, with further 25 times bent, although the responsivity decay, we can still get a good reproducibility and stability.

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43

Chowdhury, Uttiya. "MOCVD growth for UV photodetectors and light emitting diodes." Thesis, 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3108487.

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44

Shi, Shang-Qing, and 施上清. "UV photodetectors based on NiO/AZO p-n junction." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/y7qyj7.

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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
106
In this study, p-n UV sensors were fabricated using alumina zinc and nickel oxide. AZO has better conductivity than ZnO, carrier concentration also increases its high-temperature stability, and then uses nickel oxide to make a p-n-type UV sensor, improving the UV light response. The first part: using radio frequency (RF magnetron sputter) to make AZO film and NiO film on the ITO glass substrate, it changes the tile number, pressure, oxygen content and thermal annealing temperature of the process. It is found that under high temperature annealing under low watts (splash parameter 30W, pressure 0.01torr, Ar:O2=12:1, annealed under vacuum 550℃) the high carrier concentration -1.1x1021(1/cm3) and resistivity3.7x10-3 (Ωcm) can be obtained, while the NiO film has the highest carrier concentration 2.1x1020 (1/cm3) and the lowest resistivity 1.93x10-1 (Ωcm) at 50W, Ar:O2=5:5, and pressure 0.0075torr. The increase of oxygen flow rate is more effective than the example, the tile number and the reduction of pressure. The resistivity is reduced and the light transmittance is analyzed by the ultraviolet / visible light spectrograph (UV/VIS/NIRspectrometers). Field emission electron microscopy (field emission scanning electron microscope, FE-SEM) is used to analyze the surface morphology of the film, the X optical diffraction spectrum (X-Ray diffraction, XRD) is used to analyze the crystallization of the film, and the fluorescence is excited by the fluorescence. Optical spectrum (photoluminescence, PL) looks at the light responseband of the component. The second part: The size of the developing element is 1mm*1mm via the yellow light, using Al as the contact electrode and irradiating the AZO/NiO ultraviolet light sensor through the 365nm ultraviolet light, it is found that the AZO is annealed under a vacuum of 550℃, and in the NiO at 50W, Components fabricated with Ar :O2 = 5:5 and pressure of 0.0075 torr have the best photocurrent of -3.220982E-5 at a bias voltage of -1.2V, a photocurrent of -2.26031x10 -5A, and a photoresponse of 3.68 A/W. The third part: select the best parameters from the previous analysis to make the p-NiO/n-Zno nanorod UV sensor. After 550℃ thermal annealing of Zno nanorod, the prepared p-NiO/n-ZnO The nanoord device has the best photocurrent of 6.35134 x 10-5A and a photo response of 11.3 A/W.

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45

Wang, Ming-yi, and 王銘毅. "Fabrication and Characterization of MgxZn1-xO Based UV Photodetectors." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/mr426v.

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碩士
國立虎尾科技大學
光電與材料科技研究所
95
In this study, MgxZn1-xO (x=0, 0.1, 0.2, 0.3 and 0.36) films have been deposited on sapphire substrates at room temperature by using radio frequency magnetron sputtering system with difference radio frequency power, sputtering pressure and oxygen flow rate. The crystallization, surface morphology and optical properties of the MgxZn1-xO thin films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM) and ultraviolet visible spectrometer (UV-VIS), respectively. From the experimental results, the optimal sputtering parameters for film were found to be, RF power of 100 W, sputtering pressure of 10 mtorr, fixed argon flow rate of 10sccm and oxygen flow rate with the Mg content increased from 4sccm at x=0 to 10 sccm at x=0.36. The transmittance of MgxZn1-xO film has over 90 % in visible light region. The optical band gap were also determined by the transmittance spectra, which increased from 3.24 eV at x=0 to 4.02 eV at x=0.36. The MgxZn1-xO (x=0~0.36) were used as the absorption layers of MSM-PDs. It can be found that dark current of MgxZn1-xO (x=0~0.36) MSM-PDs were 5.6 pA (x=0.36) to 15.4 pA (x=0), at a 10 V bias. At a 10 V bias, a high photoresponsivity of 0.57, 0.36, 0.31, 0.27, and 0.25A/W was achieved at x=0 (380nm) to x=0.36 (310nm), respectively.

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46

Liou, Ruei-Hong, and 劉瑞鴻. "Bi-layer ZnO Nanotubes/Ultra-nanocrystalline Diamond Films for UV photodetectors." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/g75nn7.

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碩士
國立臺灣科技大學
電子工程系
104
In this study, the effect of argon and hydrogen plasma post treatment on the modification of surface morphology, electrical conductivity and photoresponse properties for nitrogen incorporated ultrananocrystalline diamond films (UNCD) were systematically investigated. Subsequently we fabricated photodetectors based on the combination of ZnO nanorods/nanotubes (ZNTs) and bilayer UNCD films as a metal-semiconductor-metal (MSM) structure. The systematic investigations have shown ultra-high photoconductive response attained from ZNTs prepared on UNCD films. The UNCD films mainly consist of wire-like diamond grains, which possesses the better photoresponse of IPhoto/IDark ratio (558) due to plasms post treatment of argon and hydrogen. Other hand, ZnO nanotubes are revealed better IPhoto/IDark(1183.3) than bare ZnO nanorods and UNCD films, since ZNTs contains large area of UV light adsorption and superior crystal quality. The bilayer combination of above materials such as ZNT/UNCD based photodetector exhibits a much higher photoresponse of IPhoto/IDark ratio (1930) after the annealing treatment of 150℃. The effect of annealing process might encased nanographitic phase among wire-like diamond grains, which formed conduction channels for efficient electron transport through large surface of ZNTs and hence led to excellent properties.

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47

GUO, JHIH-SIANG, and 郭智翔. "Study for the UV Photodetectors Based on Cu-doped ZnO Nanorods." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9q9ygr.

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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
107
In this study, we focus on the preparation of uv photodetectors with zinc oxide nanorods structure, and doped zinc oxide nanostructures with different concentrations of copper ions by simple and low-cost hydrothermal method. We discuss how to successfully fabricate stable and well-characterized uv photodetectors. The main research can be divided into two parts: The first part: plating apparatus using RF magnetron sputtering (Radio frequency, magnetron sputtering) on the glass substrate in sputtering a layer of Zinc Oxide film as seed layer, and in the configuration of zinc nitrate (Zn(NO3)2‧6H2O), hexamethylenetetramine (HMTA) concentrations of acetic acid copper (Cu(CH3COO)2) solution, using different containers, different doping concentration, growth of different nanostructures, then , by thermal annealing treatment, to reduce the lattice mismatch and so on, High Resolution Scanning Electron Microscope (HR-SEM) and Energy Dispersive Spectrometer (EDS), X-Ray Diffractometer (XRD), UV/Visible light Spectrophotometer (UV/Visible), Photoluminescence spectrum (PL), High Resolution Analytical Electron Microscope (HR-AEM) on the instrument, to the type of copper acetate doped nano structure of Zinc Oxide, Composition, lattice, optics and so on, the material characteristics are analyzed, and the better concentration is discussed. The second part: through photolithography technology, the definition of regional growth in the silicon substrate, instrument by RF sputtering, sputtering a layer of Zinc Oxide film as seed layer by hydrothermal method, and the growth characteristics of better conditions, preparation of one-dimensional (1D) nanostructures with one-dimensional nanostructures the ratio of length to width and large area of UV adsorption conditions, to improve the response of sensor element. In this study, we found that the structure of nano-pillars grown with zinc nitrate and hexamethylenetetramine at 0.025 M and 0.05 M, while copper acetate at 0.001 M, 0.003 M, 0.005 M and 0.007 M was the best at 95 oC for 3 hours, and copper doped with 0.003 M ultraviolet light had good ultraviolet response. Therefore, the analysis of copper doping has a far-reaching impact on the future components.

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48

Chang, Tang-Lung, and 張天龍. "Sol-gel process prepared MgxZn1-xO films and theirapplication to UV photodetectors." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/wju92j.

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Abstract:

碩士
國立虎尾科技大學
光電與材料科技研究所
96
Zinc oxide is a II-VI semiconductor material with direct band-gap of 3.37 eV corresponding to the wavelength in the ultraviolet region. ZnO also has large exction binding energy (~60 meV). In addition, ZnO has low resistivity and high transparency in the visible region. As a result, ZnO is considered as a promising material for the application of the optoelectronics. The MgxZn1-xO thin films were prepared on corning glass substrates by sol-gel method. X-ray diffraction (XRD), UV–vis transmittance specra (UV-VIS), Field-emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM) and photoluminescence spectrum (PL) were used to characterize the structural and optical properties of the MgxZn1-xO thin films. From the the XRD patterns, it shows that all of MgxZn1-xO films at different Mg content showed the hexagonal wurtzite structure. The XRD peak of ZnO (002) reflection shifts to the larger 2θ angle with increasing concentration of Mg in MgxZn1-xO thin films. The average transmittance in the visible region is higher than 70% for MgxZn1-xO films. It was found that the optical absorption edge has a blue shift with an increase of Mg dopant as shown in the transmission spectra. The optical band gap were determined by the transmittance spectra, which increased from 3.28 eV at x=0 to 3.52 eV at x=0.16. The optical band gap increases with increasing Mg doping in ZnO films. The MgxZn1-xO thin films were then used as the absorption layers of MSM-PDS. It can be found that dark current of MgxZn1-xO MSM-PDs were 637 nA(x=0) to 0.185 nA(x=0.16) at 10 V bias. The dark current obviously decreases three orders of magnitude with increasing Mg doping. The dark current of the MSM-PDS showed good Schottky contacts. From the photoresponse measurements, it is observed that the responsivity of UV region shifts toward the shorter wavelength side with increasing Mg doping. ZnO nanorods were synthesized on MgxZn1-xO thin films through chemical-liquid deposition technique. The diameter, vertical alignment, crystallinity, and density of ZnO nanorods are found to be strongly dependent on the content of Mg doping in the MgxZn1-xO thin films. The Mg doping in MgxZn1-xO thin films could influenced the grain size of films, which resulted in the change in diameter of ZnO nanorods. The x-ray diffraction results indicate that ZnO nanorods are high-quality single crystals growing along the c-axis direction. From the x-ray diffraction pattern, the intensity of (002) plane will become larger with increasing Mg doping in MgxZn1-xO films. From the photoluminescence spectrum, the intensity of UV emission of ZnO nanorods becomes larger and green emission becomes lower with increasing Mg doping in MgxZn1-xO films. From Selected area electron diffraction (SAED) and transmission electron microscopy (TEM) analysis, the individual nanorod is single crystal and grows along the [002] orientation.

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49

Chang, Bin-Cheng, and 張斌程. "Characterization and Fabrication of UV Photodetectors with Selective Grown Lateral ZnO Nanorods." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/zhywb6.

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Abstract:

碩士
國立虎尾科技大學
光電與材料科技研究所
103
This study will be divided into two parts to be discussed, the first part of the discussion in the form of a one-dimensional (One-dimensional) lateral zinc oxide nanorods (ZnO nanorods: ZnO NRs) morphology, different concentrations on morphology and growth time testimony analysis. The second part is the growth of lateral (Selective grown lateral) gold nanorods of zinc oxide and a half gold detectors (metal-semiconductor-metal photodetectors; MSM PDs) constituency, this part of the element for measuring IV characteristics of the light responsiveness analysis. The experiment by lithography process and RF magnetron sputtering (radio frequency magnetron sputtering) system nucleation layer portion of the zinc oxide nanorods grow nanorods position in favor of the constituency has grown as a lateral direction. We were prepared using a low temperature aqueous solution of zinc oxide nanorods laterally and can be freely controlled diameter and length according to the mask is defined to achieve the coupling between the two electrodes, the use of single crystal nanorods substantial increase in the structural characteristics of the electron transfer rate, boost element the properties In this paper, the use of aluminum (Al) as a contact electrode, via X-ray diffraction spectrum analysis (XRD), high resolution transmission electron microscope (High-Resolution Transmission Electron Microscope, HR-TEM), component analysis in material part (energy-dispersive spectrometry: EDS) and field emission electron microscope (FE-SEM) test lateral nanorods quality. On the morphology analysis, in the case of controlling the concentration of the growth time, the study found that zinc nitrate (Zinc nitrate) ratio of hexamethylene Fourth Ring Ann (HMTA) at a concentration of 0.04, the growth time for the next six hours one of the most perfect shape, flat shape and can be connected to two electrodes complete used as the channel layer element. In light detector (Photodetector) section, found zinc oxide column transverse optical detection element at a concentration of Zinc nitrate: HMTA = 0.04: 0.04 and growth time should have a high degree of light (Responsivity) 6 hours 13.87 A / W wherein the ratio of ultraviolet to visible light are mutually exclusive (UV-to-visible rejection ratio; R380 / R450) to reach 103.63. In any case, in these studies via a simple and low-cost technologies to produce zinc oxide as a base material component in the future with the development of integrated optoelectronic integrated circuits (OEIC, OptoElectronic Integrated Circuits).

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50

Liou, Jung-Shan, and 劉榕珊. "Study and fabrication of two types of wide-bandgap semiconductor-based UV photodetectors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4k2p5r.

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Abstract:

碩士
國立臺灣科技大學
電子工程系
104
The ultraviolet (UV) is easy to be absorbed by various materials because its high energy and short wavelength. Because of the small bandgap and low responsivity, the traditional semiconductor material is difficult to be fabricated as UV photodetector. Hence, in this paper, we study two types of wide-bandgap semiconductor-based: gallium nitride (GaN) and gallium oxide (Ga2O3). We design GaN-based phototransistors and Ga2O3-based photoconductors with respective structure to fabricate and measure UV photodetectors . As a result, the fabrication of two types of semiconductor-based UV photodetectors, the peak external quantum efficiency (EQE) can be more than 500% and the peak responsivity is 1.77 A/W for GaN-based phototransistors at a reverse bias of 1.56 V. The peak EQE can be more than 1800% and the peak responsivity is 5.7 A/W for bias voltages up to 4.71 V with its peak-wavelength is about 382 nm and the cut-off wavelength is about 415 nm. For Ga2O3-based photoconductors at the wavelength of 254 nm light irradiation, at a bias voltage of 5 V, the EQE about 48%, corresponding to the average responsivity of 0.1 A/W; when the bias voltage up to 15V, the best EQE is 4604%, corresponding to responsivity of 9.43 A/W. The EQE measured by the two types of semiconductor-based structures are more than 100%, which proves that the element has a high internal gain.

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