Rozprawy doktorskie na temat „Ultraviolet Photodetector”

Modern studies on charge transfer reaction and conductivity measurements of DNA have shown that the electrical behavior of DNA ranges from that of an insulator to that of a wide bandgap semiconductor. Based on this property of DNA, a metal-semiconductor-metal photodetector is fabricated using a self-assembled layer of deoxyguanosine derivative (DNA base) deposited between gold electrodes. The electrodes are lithographically designed on a GaN substrate separated by a distance L (50nm < L < 100nm). This work examines the electrical and optical properties of such wide-bandgap semiconductor based biomaterial systems for their potential application as photodetectors in the UV region wherein most of the biological agents emit. The objective of this study was to develop a biomolecular electronic device and design an experimental setup for electrical and optical characterization of a novel hybrid molecular optoelectronic material system. AFM results proved the usage of Ga-Polar substrate in conjugation with DG molecules to be used as a potential electronic based sensor. A two-terminal nanoscale biomolectronic diode has been fabricated showing efficient rectification ratio. A nanoscale integrated ultraviolet photodetector (of dimensions less than 100 nm) has been fabricated with a cut-off wavelength at ~ 320 nm.

Дана дипломна робота присвячена розробці вимірювача ультрафіолетового випромінювання, в якому використовується розроблений фотодіод на основі поверхнево-бар’єрної структури p-Cu1.8S/n-CdS з фоточутливою складовою на основі сульфіду кадмію CdS. В роботі представлений огляд науково-технічної інформації про детектори ультрафіолетового випромінювання та матеріали, які використовують для розробки первинних перетворювачів як окремих різновидів приладів та пристроїв, їх основні параметри та характеристики, підтверджена перспективність розробки. Розроблена схема електрична структурна схема електрична принципова та проведено моделювання печатної плати в програмному середовищі KiCad EDA., на основі чого був проведений підбір елементів схеми та компонування. Розроблено програмне забезпечення в програмному середовищі AtmelStudio7. Також був проведений розрахунок собівартості приладу.
This thesis is devoted to the developers of ultraviolet radiation meters, in the case of using an updated photographic film based on the surface-bar structure p-Cu1.8S / n-CdS with a photosensitive component based on cadmium sulfide CdS. The review of scientific and technical information about ultraviolet detectors and materials that provide the development of primary transducers as separate types of devices and devices, their main parameters and characteristics, confirmed by promising development. The scheme of the electric structural scheme of the electric basis is developed and the modeling of the printed circuit board in the KiCad EDA software environment is carried out. Developed software in the AtmelStudio7 software environment. The conversation about ourselves was also expanded.

Nanotechnology comprises of the understanding and control of materials and processes at the nanoscale. Among various nanostructured materials, semiconducting nanowires attract much interest for their novel physical properties and potential device applications. The unique properties of these nanowires are based on their high surface to volume ratio and quantum confinement effect. Zinc oxide, having a direct, wide bandgap and large exciton binding energy, is highly appealing for optoelectronic devices. Due to excellent optical and electrical properties, zinc oxide nanowires have been utilized to fabricate various devices such as solar cells, light emitting diodes, transistors and photodetectors. Furthermore, zinc oxide, in its natural state exhibits n-type conductivity. Addition of impurities often leads to remarkable changes in their electrical and optical properties, which open up new application areas. Among the many synthesis methods for zinc oxide nanowires, hydrothermal method is an attractive one due to its easy procedure, simple equipment and low temperature requirements. In this thesis, zinc oxide nanowires were grown and doped by hydrothermal method. Different metal dopants such as copper, silver and aluminum were used for this purpose. These metals were selected as dopants due to their effect on magnetic properties, p-type conduction and electrical conductivity of ZnO nanowires, respectively. Doped nanowires were fully characterized and the changes in their physical properties were investigated. In addition, hydrothermally synthesized pure and aluminum doped zinc oxide nanowires were used as the electrically active components in ultraviolet photodetectors. Silver nanowires were utilized as transparent electrodes. Optoelectronic properties of the detectors were examined. Effect of in-situ annealing and nanowire length was investigated. Short recovery time, around 4 seconds, with a decent on/off ratio of 2600 was obtained. This design provides a simple and cost effective approach for the fabrication of high performance ultraviolet photodetectors.

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.

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

Zinc oxide, with its direct wide bandgap and high exciton binding energy, is a promising material for optoelectronic devices. Quantum confinement effect and high surface to volume ratio of the nanowires imparts unique properties to them and makes them appealing for researchers. So far, zinc oxide nanowires have been used to fabricate various optoelectronic devices such as light emitting diodes, solar cells, sensors and photodetectors. To fabricate those optoelectronic devices, many different synthesis methods such as metal organic chemical vapor deposition, chemical vapor deposition, pulsed laser deposition, electrodeposition and hydrothermal method have been explored. Among them, hydrothermal method is the most feasible one in terms of simplicity and low cost. In this thesis, hydrothermal method was chosen to synthesize zinc oxide nanowires. Synthesized zinc oxide nanowires were then used as electrically active components in light emitting diodes and ultraviolet photodetectors. Hybrid light emitting diodes, composed of inorganic/organic hybrids are appealing due to their flexibility, lightweight nature and low cost production methods. Beside the zinc oxide nanowires, complementary poly [2- methoxy -5- (2- ethylhexyloxy) - 1,4 -phenylenevinylene] MEH-PPV and poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) hole conducting polymers were used to fabricate hybrid light emitting diodes in this work. Optoelectronic properties of the fabricated light emitting diodes were investigated. Zinc oxide emits light within a wide range in the visible region due to its near band edge and deep level emissions. Utilizing this property, violet-white light emitting diodes were fabricated and characterized. Moreover, to take advantage over the responsivity of zinc oxide to ultraviolet light, ultraviolet photodetectors utilizing hydrothermally grown zinc oxide nanowires were fabricated. Single walled carbon nanotube (SWNT) thin films were used as transparent electrodes for the photodetectors. Optoelectronic properties of the transparent and flexible devices were investigated. A high on-off current ratio around 260000 and low decay time about 16 seconds were obtained. Results obtained in this thesis reveal the great potential of the use of solution grown zinc oxide nanowires in various optoelectronic devices that are flexible and transparent.

Capacitance-voltage-frequency measurements on n+-GaN/AlxGa1−xN UV/IR dual-band detectors are reported. The presence of shallow Si-donor, deep Si-donor, and C-donor/N-vacancy defect states were found to significantly alter the electrical characteristics of the detectors. The barrier Al fraction was found to change the position of the interface defect states relative to the Fermi level. The sample with Al fraction of 0.1 shows a distinct capacitance-step and hysteresis, which is attributed to C-donor/N-vacancy electron trap states located above the Fermi level (200 meV) at the heterointerface; whereas, the sample with Al fraction of 0.026 shows negative capacitance and dispersion, indicating C-donor/N-vacancy and deep Si-donor defect states located below the Fermi level (88 meV). When an i-GaN buffer layer was added to the structure, an anomalous high-frequency capacitance peak was observed and attributed to resonance scattering due to hybridization of localized Si-donor states in the band gap with conduction band states at the i-GaN/n+-GaN interface.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A presente pesquisa teve como principal objetivo a obtenção de estruturas nanométricas de óxido de índio, óxido de estanho e óxido de zinco por evaporação térmica e síntese hidrotérmica e a construção e teste de sensores de gases e de fotodetectores de ultravioleta baseados nessas nanoestruturas. Foram realizados estudos da influência dos parâmetros experimentais das duas rotas de síntese usadas sobre as morfologias e as propriedades das estruturas. Para a obtenção das camadas nanoestruturadas por evaporação térmica foi especialmente construído um forno tubular que permitiu o controle da temperatura de deposição independente da temperatura de evaporação e da distância entre a fonte de evaporação e o substrato. Esses parâmetros, pouco explorados nas pesquisas reportadas na literatura, exerceram uma grande influência sobre a morfologia e as propriedades dos nanofios obtidos. O equipamento permitiu ainda um controle preciso da composição da atmosfera e da pressão de síntese. Na síntese química em solução, a construção de um reator hidrotérmico permitiu o estudo da influência da taxa de resfriamento sobre as dimensões, cristalinidade, morfologia e propriedades das nanoestruturas. Esse estudo, o primeiro do gênero na literatura, ressaltou a importância no controle deste parâmetro para sintetizar estruturas com propriedades melhoradas. As demais variáveis estudadas foram: a concentração das soluções, as camadas catalisadoras, a temperatura e o tempo de síntese. Foram testadas duas estratégias para a obtenção dos filmes nanoestruturados: spin-coating de suspensões de nanoestruturas sobre substratos de silício oxidado ou o crescimento das mesmas, durante a síntese, sobre substratos com camadas catalisadoras de zinco. Os nanofios e as camadas funcionais foram caracterizados por Difração de Raios-X (DRX), Microscopia Eletrônica de Varredura...
The subject of this thesis covers the synthesis and growth of indium, tin and zinc oxide nanostructures by thermal evaporation and hydrothermal synthesis and the fabrication and testing of gas sensors and ultraviolet photodetectors based on these nanosized structures. For both chemical and physical routes, the influence of processing conditions over the morphology, dimensions and electrical properties of the nanowires was investigated. In order to obtain nanostructured layers by thermal evaporation a tubular furnace was specifically builti, allowed the control of the source-substrate distance and the deposition temperature independently of the evaporation one. These parameters, slightly explored in the literature, granted a big influence over the nanowires morphology and properties. Moreover, the equipment permitted the control of deposition atmosphere and pressure. The design and assembly of a hydrothermal reactor allowed studying the influence of the cooling rate over the dimension, morphology, cristallinity and, consequently, the properties of the nanostructures. This study highlighted the importance of controlling this particular parameter in the hydrothermal process, yielding nanostructured materials with enhanced properties. Variables such as solution concentration, synthesis temperature and time, surfanctants and precursors were also explored in the hydrothermal process. In order to obtain nanostructured thin films using the chemical bath deposition, two processing techniques were employed: spin-coating of powder suspensions over oxidized silicon substrates and nanostructured anisotropic growth directly from solution using zinc coated substrates. The nanowires and the functional nanostructured layers were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE - SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS)... (Complete abstract click electronic access below)

Resumo: A presente pesquisa teve como principal objetivo a obtenção de estruturas nanométricas de óxido de índio, óxido de estanho e óxido de zinco por evaporação térmica e síntese hidrotérmica e a construção e teste de sensores de gases e de fotodetectores de ultravioleta baseados nessas nanoestruturas. Foram realizados estudos da influência dos parâmetros experimentais das duas rotas de síntese usadas sobre as morfologias e as propriedades das estruturas. Para a obtenção das camadas nanoestruturadas por evaporação térmica foi especialmente construído um forno tubular que permitiu o controle da temperatura de deposição independente da temperatura de evaporação e da distância entre a fonte de evaporação e o substrato. Esses parâmetros, pouco explorados nas pesquisas reportadas na literatura, exerceram uma grande influência sobre a morfologia e as propriedades dos nanofios obtidos. O equipamento permitiu ainda um controle preciso da composição da atmosfera e da pressão de síntese. Na síntese química em solução, a construção de um reator hidrotérmico permitiu o estudo da influência da taxa de resfriamento sobre as dimensões, cristalinidade, morfologia e propriedades das nanoestruturas. Esse estudo, o primeiro do gênero na literatura, ressaltou a importância no controle deste parâmetro para sintetizar estruturas com propriedades melhoradas. As demais variáveis estudadas foram: a concentração das soluções, as camadas catalisadoras, a temperatura e o tempo de síntese. Foram testadas duas estratégias para a obtenção dos filmes nanoestruturados: spin-coating de suspensões de nanoestruturas sobre substratos de silício oxidado ou o crescimento das mesmas, durante a síntese, sobre substratos com camadas catalisadoras de zinco. Os nanofios e as camadas funcionais foram caracterizados por Difração de Raios-X (DRX), Microscopia Eletrônica de Varredura... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The subject of this thesis covers the synthesis and growth of indium, tin and zinc oxide nanostructures by thermal evaporation and hydrothermal synthesis and the fabrication and testing of gas sensors and ultraviolet photodetectors based on these nanosized structures. For both chemical and physical routes, the influence of processing conditions over the morphology, dimensions and electrical properties of the nanowires was investigated. In order to obtain nanostructured layers by thermal evaporation a tubular furnace was specifically builti, allowed the control of the source-substrate distance and the deposition temperature independently of the evaporation one. These parameters, slightly explored in the literature, granted a big influence over the nanowires morphology and properties. Moreover, the equipment permitted the control of deposition atmosphere and pressure. The design and assembly of a hydrothermal reactor allowed studying the influence of the cooling rate over the dimension, morphology, cristallinity and, consequently, the properties of the nanostructures. This study highlighted the importance of controlling this particular parameter in the hydrothermal process, yielding nanostructured materials with enhanced properties. Variables such as solution concentration, synthesis temperature and time, surfanctants and precursors were also explored in the hydrothermal process. In order to obtain nanostructured thin films using the chemical bath deposition, two processing techniques were employed: spin-coating of powder suspensions over oxidized silicon substrates and nanostructured anisotropic growth directly from solution using zinc coated substrates. The nanowires and the functional nanostructured layers were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE - SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS)... (Complete abstract click electronic access below)
Orientador: Maria Aparecida Zaghete Bertochi
Coorientador: Elson Longo
Banca: Antonio Ricardo Zanatta
Banca: Mônica Alonso Cotta
Banca: Talita Mazon Anselmo
Banca: Sidney José Lima Ribeiro
O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp
Doutor

碩士
大葉大學
電機工程學系碩士班
93
In this experimental process, we deposit oxide layer on GaN with liquid-phase deposition. And we change the ration of hydrofluosilicic (H2SiF6) solution and boric acid to analyze the mode on the surface of silicon dioxide with AFM. To investigate the chemical bonding with ESCA and the composition with EDS & AES of SiO2 makes sure the possible chemical elements. Compared the as-deposited and annealing in 800℃for 1hour among different deposited time. Annealing can harden silicon dioxide and decrease the leakage current of 2.7x10-2A/cm2 as-deposited to 7.77x10-3A/cm2 as annealing. We obtain higher electric breakdown field over 3.5 MV/cm2 and the leakage current is about 10-5 A/cm2 at 0.8 MV/cm2. Compared the photodetector with dark, and the 254 nm & 366 nm of ultralight gain the photodark-current ratio 20.

碩士
國立中山大學
電機工程學系研究所
98
In this study, we prepare the zinc oxide nanotip with aqueous solution on Al doped ZnO/glass substrate. In excess of 6 hours growth, the film-liked layer is obtained in the bottom of ZnO nanotip. In order to study the photoresponse of maximum ZnO nanotip length without film-like layer, we choose 6 hours as the growth time of ZnO nanotip, which the height is almost the same of about 4 μm. For the fabrication of ZnO nanotip UV photodetector, In-Zn was use as anode and cathode electrodes in digitate type on the top of ZnO nanotip array. The photoresponse which use AZO buffer layer of 300 s is better than others due to the larger surface to volume ratio. We obtain that Ron/off is 10.9, rise time is 280 s, and decay time is 870 s. The thermal annealing at 300 °C in N2, O2, and N2O for 1 hr can improve the photoresponse, because the Zn(OH)2 in the ZnO nanotip gets converted into ZnO. Among annealing ambiences, the annealed ZnO nanotip in N2O show higher performance due to high decomposition of O atoms, which fills in the oxygen vacancy. We obtained that Ron/off is 26.04, rise time is 50 s, and decay time is 70 s at 300 oC in N2O.

碩士
逢甲大學
電子工程學系
106
In this research, we designed a new structure of UV Photodetector, we use a non-vacuum environment, low cost and fast production of Ultrasonic spray pyrolysis deposition (USPD) technology to deposit MgZnO thin films, and use this technology to fabricate Semiconductor-Metal-Semiconductor Dual Band Ultraviolet Photodetector, then use of three different electrode Metal, Al ,Au and Ni/Au to observe the characteristics of devices. First of all, for the material characteristics analysis of MgZnO film, the analysis content is as follows : (1) X-ray photoelectron spectrometer (XPS) analysis of chemical qualitative and quantitative characteristics; (2) X-ray diffraction (XRD) analyzer analysis of crystal structure; (3) Photoluminescence spectrometer (PL) analysis of film defect trap energy level depth; (4) Ellipsometer analyzes the refractive index and the extinction coefficient. (5) UV/Visible/NIR spectrophotometer analysis of optical absorption. (6) Atomic force microscopy (AFM) analysis of surface morphology. (7) Transmission electron microscope (TEM) observation of the depth distribution. Secondly, developed a MgZnO Ultraviolet Photodetector with dual-band sensing capabilities, and analyzed its photo/dark current, photo/dark current rejection ratio, switching time analysis, spectral responsivity analysis, and specific detectivity analysis. In the study, it was found that the use of USPD technology to deposit MgZnO thin films, and the production of a Dual Band Ultraviolet Photodetector, regardless of whether the metal it plated is Al or Au, its dark current will decrease according to the increase of magnesium content, and two bands can be clearly found in the spectral responsivity schematic and the specific detectivity schematic of all structures. USPD of MgZnO Dual Band Ultraviolet Photodetector has great potential for future industrial applications.

碩士
國立成功大學
光電科學與工程研究所
98
In this study, we demomstrated a single AlGaN layer with two different Al contents on the GaN μ-pillars template. It was found by the selective wavelength spatial cathodoluminescence images that the emission wavelength of the AlGaN layer were at 340 and 320nm on the side of the cone and on the top and valley surface of pillars, respectively. The Schottky-type photodector were also demonstrated on double Al contents of deposited AlGaN on GaN micropillar template. The three steps of response occurred at about 326, 346, and 356nm with responsivities of 1.1×10-2, 5.9×10-3, and 4.04×10-3 A/W, respectively. However, the pits formation might arise from the lattice mismatch and the higher strain of AlGaN layer on sidewall of GaN pillar, resulting in the larger leakage current. In order to restrain the leakage current and improve the performances, we treated out the surface on sample with (NH4) 2Sx .We found that after (NH4) 2Sx treatment might result in a decrease in the carrier concentration and optical bandgap of ITO film. The effects of an (NH4) 2Sx treatment could change the properties of ITO films and form sulfide passivation for the enhancement of the schottky barrier height.

碩士
國立屏東科技大學
機械工程系所
98
In this thesis, the ultraviolet (UV) photodetector is fabricated using metal - semiconductor – metal sturcture. The Zinc Oxide (ZnO) thin films is chosen as the active layer, which the material and optical properties are investigated. This thesis is mainly comprising two major parts: (a) preparation of ZnO thin films and analysis of the material properties. (b) fabrication of ultraviolet photodetector with the active layer of ZnO thin film by using the metal - semiconductor - metal structure, and the measurement of electrical properties using the same. (a)Preparation of ZnO thin films and analysis of material properties In this thesis, the prepared ZnO thin film is a kind of material which can be applied in the UV Photodetector. The ZnO film is a semiconductor material with band gap of 3.37 eV. In the manufacturing process, the ZnO film is deposited on the p-type silicon wafer substrate by RF (sputter) method. In this thesis, the thickness of ZnO thin film and sputtering power density are chosen as the process parameters. Finally, the effect of power density and thickness of the ZnO thin film are analyzed using SEM, AFM, XRD, UV and other analytical instruments. (b)Fabrication of UV Photodetector with the active layer of ZnO using structure of made of metal - semiconductor - metal structure, and the measurement of its electrical properties. The contact electrodes are fabricated on the the prepared ZnO thin film by using the standard photolithography process including the steps of RCA Clean, photoresist coating, exposure and development, Finally, the photo current and dark current was measured by using I-V measurements. It is clearly observed that the optimum photo/dark current ratio of four orders can be obtained under the thickness of 750 nm and the sputtering power density of 2.55 W/cm2 where the bias is formed as 6 volts.

碩士
國立中央大學
光電科學研究所
95
Due to the high resistance of P-type semiconductor, We have to deposit a Transparent Conduct Layer (TCL) as a Current Spreading Layer and a Electrode at the same time. However, TCL absorbs some power from the incident light that reduces the performance of photo-detectors（PDs）. Therefore, the aim of this article attempts to explore how mesh electrode increases the responsivity of PD by reducing the absorbing power of TCL. In this experiment, GaN、AlGaN and AlGaN with window Layer GaN-based PIN wafer were prepared. Then we deposited Ni/Au and ITO as TCLs. Finally, we made TCLs into Planar and Mesh structures. Results of this study showed mesh TCL raises the responsivity of PDs. Although the quantity of improvement on responsivity is related to the transmittance of TCLs and the cut-off wavelength of PDs, We still have up to 24% raise on AlGaN PDs. To conclude, since transmittance of TCLs is not so well in wavelength UV-B（320nm~280nm） and UV-C（below 280nm）, applying of mesh TCLs will get better improvement on responsivity.

博士
國立成功大學
材料科學及工程學系碩博士班
100
Fabrication of high-performance ZnO nanowire-based photodetectors through low temperature processes is the main purpose of this dissertation. For this purpose, a wet chemical process was employed as the main technique for synthesizing ZnO nanowires. Besides, the morphology and size of ZnO nanowires were tuned by the addition of PVA with varied amount. PVA acts as a structure-directing agent for growing the ultra-long ZnO nanowires. Then, the ZnO UV photdetectors were fabricated by aligning ZnO nanowires between the interdigitated electrodes via a dielectrophoresis process. Based on decreasing the reflection of UV light on ZnO surface, the signal to noise ratio can be improved via capping PMMA micro-lens arrays. Then Ag nanoparticles were loaded onto the surface of ZnO nanowires by a photoreduction process, for the purpose of decreasing the response time. By investigating the Ag/ZnO interface, a non-stoichiometric AgOx phase is observed by HRTEM images and SAED patterns. Ag2O nanoparticles were also decorated onto the surface of ZnO nanowires. Photogenerated electrons and holes can be separated by the built-in potential induced by Ag2O/ZnO p-n junction. After decorating Ag2O nanoparticles onto ZnO surface, the maximum signal to noise ratio is larger than 105, accomplishing both a short rise time and a decay time of less than 1 s. After turning off UV irradiation, the current of Ag2O/ZnO heterostructured UV detector is recovered to the initial value within around 10~13s. The aqueous solution processes were also used to self-assemble ZnO nanobridge photodetcors. By investigation with XPS and PL, singly ionized oxygen vacancies induce the persistence photoconductivity of ZnO-nanowire-based UV photdetectors. A hydrothermal process was used to passivate the surface states and singly ionized oxygen vacancies on the ZnO nanowires. The photoresponse time decreases significantly after extending the hydrothermal duration.

碩士
國立虎尾科技大學
光電與材料科技研究所
97
Today, there are many different types of the surface acoustic wave devices, has been widely used in communications and sensors of variety, but in general in order to enhance the effects of components will use the high electromechanical coupling coefficient of piezoelectric material, enable to use such as the mass lodaing or acoustoelectric response as the principle of the sensor. In this study, to utilized zinc oxide excellent photo-electric and piezoelectric properties of the coupling surface acoustic wave devices generated acoustoelectric response to produced the surface acoustic wave ultraviolet sensor, and used lithography process and RF magnetron sputtering system to deposited metal electrodes and zinc oxide thin film on ST-cut quartz and Y-cut lithium niobate substrate, can be obtained zinc oxide thin film with a high c-axis preferred orientation, used to fabrication the surface acoustic wave devices. To utilized chemicals hydrothermal method to synthetize different zinc oxide nanorods, and to investigate different solution concentration and seedlayer thickness effect of the characteristics of zinc oxide nanorods, and such as a enhance the absorption of ultraviolet light structure, in order to produce high sensitivity of surface acoustic wave ultraviolet sensor can detect a sense μW/cm2 of hierarchy ultraviolet source, in the study to explore the structure of the production of surface acoustic wave devices at the different substrates and different metal electrodes, as well as different growth times of zinc oxide nanorods of under different wavelengths UV source, the frequency response of the devices and the impact on the DC characteristics, to explore its characteristics of surface acoustic wave devcies and comparison of the measured results. Keywords：Zinc oxide; Nanorod; SAW; photodetector

碩士
國立虎尾科技大學
電子工程系碩士班
102
The titanium dioxide thin films were deposited on quartz and LiNbO3 by radio frequency magnetron sputtering. Titanium dioxide thin film was post-annealing in a vacuum environment to obtain a homogeneous dense structure. Titanium dioxide nanorod arrays were grown by hydrothermal method, the concentration of aqueous solution and growth time were changed to increase the absorption capacity. The surface morphology, crystal structure and luminescence properties were analyzed using field emission scanning electron microscopy, X-ray diffraction and photoluminescence spectroscopy. The titanium dioxide thin film with nanorod arrays was applied to a surface acoustic wave ultraviolet photodetector. The insertion loss, phase, resistance, and capacitance of devices were measured by network analyzer and impedance analyzer.

III-Nitride semiconductor devices reserve their utmost place in the ubiquitous class of technology due to its applicability in a wide range of applications, which include solar cells, light-emitting diodes (LEDs), laser diodes (LDs), photodetectors (PDs), etc. Consequently, the extensive range of applications and projected gigantic market size generates continuous demand for more efficient, durable, and quality device products. The researchers have world-wide taken up this challenge of the never-ending requirement of technological improvisation and devoting their rigorous efforts to achieve better materials quality and device design. Among numerous domestic, commercial, and defence applications of III-nitride semiconductor-based devices, the detection of harmful ultraviolet (UV) radiation (<400 nm) found to be an extreme necessity. Universally, technologist finds potential needs to detect UV for plume detection, flame detection, chemical as well as biological analyses, secure space to space communications, environmental monitoring, astronomical research, and antimissile technology. Thus, the recommended ideal photodetector (PD) device should be adverse environment friendly with excellent sensitivity, high responsivity, high signal to noise ratio, and high spectral selectivity. Henceforth, as compared to conventional Sibased UV PD devices, III-nitride is proven to be a promising candidate due to their remarkable credentials such as wide-direct bandgap, high thermal conductivity, superb radiation hardness, which makes them operable in harsh environmental conditions. Besides, the detectors with Si-based technology severely loses signal to noise ratio as well as efficiency as a function of increasing dark current with elevated temperature. The solution to these problems has been provided by usage of the bulky cooling arrangement, expensive optical filters, and their operational instrumentation setups. Therefore, the movement of the semiconductor market from the Si-based to III-nitride based can be well understood. However, a key challenge is the presence of a large density of defects and dislocations due to lack of suitable lattice-matched substrates, and low resistance Ohmic contacts. Thus, particularly in the case of energy-efficient UV PD fabrication, the curiosity to grow good quality epitaxial III-nitride films has been mainly directed towards the study on GaN nanostructures (NSs). Thereby, the xiv growth of high surface to volume ratio based GaN NSs increases the incident photon absorption sites without sacrificing the device nano dimensionality. Besides, the possibility of integration of GaN with existing Si-based device technology leads us towards growth & fabrication on Si (111) substrates. Till date, numerous methodologies have been adopted to grow and optimize stress relaxed, higher aspect ratio, high crystalline quality as well as an excellent opto-electrical transport based GaN NSs by using plasma-assisted molecular beam epitaxy (PAMBE). Despite improvisation in crystalline quality, grown NSs as well as device geometry, recent advancement for enhancing the performance of PD devices emphasized on other exciting and potential approaches such as hybridization of III-nitride materials with other UV sensitive semiconductors, functionalization by novel metal nanoparticle’s nanoplasmonics and sensitization by highly conductive quantum dots. Thus, the thesis aims to explore and meticulously investigate the precise control epitaxial growth of high surface to volume ratio oriented GaN NSs on Si (111) substrate using the PAMBE system and their utilization as energy-efficient UV PDs. Besides, the effort made in this work excavates and execute the new prospects for emerging next-generation highly efficient photodetectors via. ZnO/GaN heterojunction hybridization, Au-NPs functionalization, and GQDs sensitization. The thesis consists of seven chapters, briefly described below: Chapter 1 gives a brief overview of the photodetection devices which are sensitive towards the UV range. Further, the significant contribution of III-nitrides in the fabrication of energy-efficient and durable UV PDs has been discussed. Moreover, the introduction of III-nitrides semiconductor’s inherent physical, chemical, optical properties with their bandgap engineering has been elaborated, which were found responsible for the fabrication of narrow to broadband PDs for harsh environment. Additionally, to enhance the performance of existing III-nitride UV PD technology, other potential approaches such as nitride’s surface functionalization, hybridization and sensitization have also been suggested. Chapter 2 describes the detailed mechanism of the technique used for the growth of III-nitride semiconductors along with various in-situ as well as ex-situ analytical tools xv and methods utilized for probing the structural, morphological, optical and electrical properties of the grown structures. This chapter illustrates a brief description of the steps involved in devices fabrication process and evaluation of their performance parameters as well. Chapter 3 elucidates the growth of nanoisland shaped, lower stress, and strain facilitated GaN-NS on Si (111) substrate via PAMBE and fabrication of GaN-NS based UV photodetection device even with NS’s tiny dimensionality. The threedimension (3D) growth of GaN-NS in real-time was observed by the in-situ RHEED technique, which displays transformation from streaky to the spotty pattern. A microRaman technique has been employed to elaborate on NS’s crystallinity and lower stress value, which is found to be in good agreement with related lower strain as evaluated by HR-XRD spectra. An observed sharp near band edge emission at 363.2 nm by room temperature photoluminescence measurement signifies the presence of GaN. After that, the as-grown ultra-thin GaN NSs were utilized to fabricate energyefficient self-powered UV PD, wherein non-homogeneous GaN nanoislands were perceived on the Si surface with a thickness of ~30 nm and an average distribution density of 2 ×1010 cm -2 . Despite nano dimensional GaN NSs film, the capability of UV detection of fabricated PD added novelty to this work, where performance parameters such as photosensitivity (~102 ), detectivity (~109 Jones), responsivity (1.76 mA/W) and NEP: noise equivalent power (3.5 × 10-11 WHz-1/2) under selfpowered mode were observed. The transient photo-response measurement revealed a rapid rise and decay time constants of ~18 ms and ~27 ms, respectively. Under varying optical power (1 mW to 13 mW), the GaN PD displayed significant enhancement in photocurrent with increasing optical power. The performance of the fabricated detector has also been analyzed under the photoconductive mode of operation, where it revealed significantly enhanced responsivity (23 fold) and detectivity (~1000 fold). Such nanostructured self-powered GaN-based UV PD paves the way towards the fabrication of energy-efficient optoelectronic devices. Chapter 4 presented the nanoplasmonic impact of chemically synthesized Au nanoparticles (NPs) on the performance of GaN NS based UV PD is analyzed. The devices with uniformly distributed Au NPs on GaN NSs (nanoislands) prominently xvi respond toward UV illumination (325 nm) in both self-powered as well as photoconductive modes of operation and have shown fast and stable time-correlated response with significant enhancement in the performance parameters. A comprehensive analysis of the device design, laser power, and bias-dependent responsivity and response time is presented. The fabricated Au NP/GaN nanoislandbased device yields the highest responsivity of ∼ 216 mA/W, detectivity of ∼ 109 jones, reduced NEP of ∼ 1.8 × 10−12 W Hz−1/2, External quantum efficiency (EQE) of ∼ 82%, and fast response/recovery time of ∼ 40 ms. Moreover, the study also illustrates the mechanism where light interacts with the chemically synthesized NPs guided by the surface plasmon to enhance the device performance effectively. Further, the decoration of low dimensional Au NPs on GaN NSs acts as a detection enhancer with fast recovery time. It paves the way toward the realization of energyefficient optoelectronic device applications. Chapter 5 elaborates on the fabrication of GaN-Nanotowers (GaN-NTs) based on highly efficient UV PD with distinct AlN buffer layer thickness and NTs lengths. The unique nanotower (tapered ended) morphology of an epitaxially grown hexagonal stacked nanocolumnar structure with truncated strain and high surface-to-volume ratio contributes to the significantly enhanced performance of the fabricated detector towards UV illumination. The fabricated GaN-NT UV PDs displays very low dark current (~12nA) & very high ILight /IDark ratio (>104 ) along with the highest responsivity of 485 A/W. The device exhibits very high EQE ~105 %, fast time-correlated transient response (~430 µs), very low NEP (~10-13 WHz-1/2), and excellent UV/Vis rejection ratio. Therefore, the utilization of such GaN-NT structures can be advantageous towards the fabrication of energy-efficient ultraviolet photodetector. Chapter 6 introduce the concept of performance augmentation of existing III-nitride (GaN) UV PDs technology employing hybridization using UV sensitive & compatible semiconductors (ZnO), surface functionalization by novel metal Gold (Au) NPs and sensitization by highly conductive graphene quantum dots (GQDs). Thereby, as grown (as discussed in chapter 5) vertically aligned longer GaN NTs with higher AlN thickness oriented highly responsive UV demonstrated fast response with excellent stability when functionalized with Au Nanoparticles, GQDs, and ZnO Nanorods. xvii Initially, GaN-NTs structure is hybridized by ZnO Nanorods (ZnO NRs), wherein, to capture maximum incident photons, a strategically formulated model of NSs over NSs has been proposed as an enhanced device active surface area. Consequently, the fabricated GaN-NTs based device with ZnO NRs hybridization, GQDs sensitization, and Au NPs functionalization significantly accelerate the performance of the device where a prominent three order reduction in dark current is observed along with gigantic R, lower NEP and enormously enhanced EQE of 7042 A/W, 1.84×10-14 W.Hz-1/2 and 2.7×106 % respectively. Mechanism elaborating the enhanced device performance with an appropriate energy band diagram has been discussed in detail. The fabricated highly sensitive device can lead a path towards future optoelectronic applications of integrated III-Nitride technology. Chapter 7 enlightens the major conclusions derived from the thesis work and the scope of future work.

博士
國立中興大學
材料科學與工程學系所
103
This research consisted of three parts, which were the growth of zinc sulfide (ZnS) films, the fabrication of GaOx photodetectors, and the preparation of ZnO photodetectors. In the first part, the ZnS films were grown by chemical bath deposition (CBD) with various Zn/S molar ratios from 1/50 to 1/150. With changing the Zn/S molar ratio from 1/75 to 1/150, the ZnS films demonstrated high transmittance of 75-88% in the visible region (360-1000 nm), and the energy bandgaps of these films were 3.85-3.86 eV. Based on the results of transmittance and adhesion of ZnS films, the optimum Zn/S molar ratio was determined to be 1/75. The X-ray photoelectron spectroscopy measurement reveals that not only ZnS but also ZnO and Zn(OH)2 phases were formed in the CBD-ZnS films. The CBD-ZnS film formed with the Zn/S molar ratio of 1/75 was highly potential for optoelectronic applications, and it was employed as the seed layer of the ZnO growth. Furthermore, monoclinic GaOx films were grown on (0001) sapphire at various substrate temperatures ranging from 400 to 1000C by pulsed laser deposition (PLD). As the substrate temperature was increased to 800C, the GaOx film possessed single crystalline phase with a preferred growth orientation of (-201) plane. Based on the results of Rutherford backscattering spectroscopy, the O/Ga ratio of GaOx film increased gradually with increasing the substrate temperature. When the substrate temperature was raised to 800-1000C, the film composition was close to the formation of Ga2O3. In addition, the films grown at 600 and 800C were chosen to fabricate solar-blind metal-semiconductor-metal (MSM) photodetectors. Under an applied bias of 5V, the photodetector prepared with 800C-grown film has a lower dark current of 1.2 × 10-11 A and a higher responsivity of 0.903 A/W (at a wavelength of 250 nm) than those with 600C-grown films. The better device performance is ascribed to the higher crystal quality and fewer O vacancies in the 800C-grown film. Finally, the PLD-ZnO samples were prepared at 500-900C on the CBD-ZnS seed layers. As the substrate temperature was heated to 500-700C, the ZnO samples belonged to the film type. However, with increasing the substrate temperature to 900C, the morphology of ZnO was changed to one-dimensional nanostructure type. This one-dimensional ZnO possessed a single crystalline phase with a preferred growth orientation of hexagonal (002) plane. According to the results of device performance, the dark currents (@1V) of the MSM photodetectors with the PLD-ZnO prepared at 500, 700, and 900C were 8.65×10-7, 4.23×10-8, and 2.15×10-7 A, respectively. Meanwhile, the photocurrents (@1V) of these three devices were 9.62×10-8, 1.26×10-6, and 4.62×10-5 A, respectively. The signal-to-noise ratios of these three devices were calculated to be 8.99, 29.8, and 214.9, respectively. This confirmed the MSM photodetector fabricated with 900C-grown ZnO nanostructure possessed better device performance.

碩士
中原大學
電子工程研究所
101
In this study, atomic layer deposition (ALD) system was used to deposit the Mg0.1Zn0.9O films as the absorption layer of the metal-semiconductor-metal ultraviolet photodetectors (MSM-UPDs). The photoelectrochemical (PEC) method was used to form a passivation layer Zn(OH)2 on the surface of the Mg0.1Zn0.9O films, which can reduce the dangling bonds and surface states on the surface of Mg0.1Zn0.9O films, which could reduce the dark current and improve low frequency noise of the Mg0.1Zn0.9O MSM-UPDs. At bias of 5 V, the dark current of the Mg0.1Zn0.9O MSM-UPDs with PEC passivation decreased from 1.81×10-9 A to 1.53×10-10 A; then devices were illuminated by incident light wavelength of 340 nm, and the light power of 39.98 μW, the ultraviolet (UV)-visible rejection ratio increased from 1.71×103 to 5.50×103, and the NEP decreased from 6.18×10-13 W to 4.27×10-13 W. Compared with the MSM-UPDs with the PEC passivation, the UV-visible rejection ratio of the MSM-UPDs with the PEC passivation and silica nanospheres anti-reflection layer could effectively increase from the 5.50×103 to 1.44×104 and the NEP could decrease from 4.27×10-13 W to 2.60×10-13 W. It was attributed to that the surface state and dangling bond were effectively passivated using PEC method, and the amount of incident light was increased by the silica nanospheres anti-reflection layer. The detectivity of the Mg0.1Zn0.9O MSM-UPDs with and without PEC passivation and Mg0.1Zn0.9O MSM-UPDs with PEC passivation and silica nanospheres coating were 5.11×1011cmHz1/2W-1、7.39×1011cmHz1/2W-1及1.21×1012cmHz1/2W-1, respectively.

碩士
國立雲林科技大學
電子工程系
103
Zinc oxide as a transparent conductive oxide, non-toxicity material, as well as have high chemical and thermal stability, in the short-wavelength which exhibits strong nature of excitonic properties. Therefore ZnO is extensively used of short-wavelength and other optoelectronic devices. In this study, the synthesis solution of zinc nitrate hexahydrate, aluminum nitrate and hexamethylenetetramine, that concentration fixed at 0.025M. The vertically aligned Al-doped ZnO nanorods were successfully grown on a glass substrate using a simple hydrothermal method, the growth temperature was kept constant at 70°C, 80°C, 90°C for 8 hour, respectively. The surface morphology of Al-doped ZnO nanorods can be observed by the field emission scanning electron microscope (FE-SEM) and Transmission Electron Microscopy (TEM), and through X-ray diffraction (XRD), Raman Scattering Spectrometer to analysis the crystal quality, it was found that doping Al do not change the structure and orientation of wurtzite-structured ZnO nanorods. Under the photoluminescence spectroscopy measurement, Aluminum doped zinc oxide have higher (IUV/IVis), it indicate that optical properties of Zinc oxide can improved by Al element doped. After the above of analysis, we can know that Al doped ZnO nanorods grown at 80 °C have excellent characteristics. Al-doped ZnO nanorods UV photodetector was prepared at temperature of 80 °C , under UV illumination, the current response of detector had high stability, and high UV-to-visible rejection ratio of 1.7019×〖10〗^4, detector also measured in air under different humidity conditions, it was found that the photo current decreases gradually under high humidity, and the photoresponse rate will accelerate as the humidity increases, the results indicated that the Al-doped ZnO nanorods UV photodetector had excellent performance.

碩士
國立虎尾科技大學
光電與材料科技研究所
98
This study enhances the ultraviolet sensitivity of Love wave photodetector using nickel－doped ZnO nanorods. The Love wave photodetector was fabricated using a ZnO guiding layer with nanorod arrays deposited on a 90°-rotated ST-cut (42°45) quartz substrate. Dense crystalline ZnO thin films were deposited by radio frequency magnetron sputtering. The nickel－doped ZnO nanorod arrays were synthesized on a ZnO thin film via the hydrothermal method. The crystalline structure, surface morphology and luminescent characteristics of films and nanorod arrays were examined by X-ray diffraction, scanning electron microscopy, and photoluminescence spectrometer. This study investigated the effects of the interaction of the Love wave with the ultraviolet light in the ZnO guiding layer on shift of insertion loss, phase shift of transmitted signal. The ultraviolet sensitivity of the Love wave photodetector was enhanced by adding nickel－doped nanorod arrays to the guiding layer.

碩士
國立中興大學
電機工程學系所
102
In this study, surface plasmon was used to enhance the optical properties of ZnO nanorods (NRs) prepared by hydrothermal method, in which the surface plasmon was achieved by depositing 4nm-thick Au nanoparticles (NPs) on the ZnO NRs surface. Simultaneously, ZnO-based Schottky and metal-semiconductor-metal (MSM) photodetectors were fabricated on p-Si subatrate. Effects of various temperatures (350 °C, 450 °C, 550 °C) anneal in 4-nm-thick Au thin film on the Schottky barrier height (SBH) and ultraviolet response were studied here. First, the morphology of Au NPs was investigated for different annealing temperatures. Atomic force microscopy (AFM) shows that with increasing in anneal temperature, the particle size of Au NPs increases and average particle size of about 35 nm as well as surface roughness of 4.24 nm are observed in Au NPs received 550 °C anneal. In terms of optical properties, light absorption and photoluminescence (PL) were measured for the samples annealed in different temperatures. Maximum absorption peak area with full width at half maximum (FWHM) of 191.06 nm are founded in the sample annealed at 450 °C. With increasing annealing temperature, the absorption peak area increases and then decreases for the 550 °C anneal. In PL spectra, the UV emission (380 nm) of samples with Au nanoparticles will be enhanced due to the surface plasmon resonance (SPR) effect. The maximum UV emission is observed for the 350 °C annealed sample. Next, Schottky and MSM photodetectors were were fabricated with wnt without Au NPs. Current-voltage (I-V) characteristics shows that the samples with Au NPs present a large leakage current and poor rectification ratio. As the annealing temperature is further increased to 550 °C, the material properties will be degraded due to more defects, leading to smaller photocurrent. Photoresponse shows that the samples with Au NPs present higher UV to visible rejection ratio more than 2 orders for both Schottky and MSM photodetectors. At -2V reverse-bias voltage, the UV to visible rejection ratio is increased from 76.97 for the samples without Au NPs to 486.64 for the samples with 450 °C anneal. Finally, Au and Al electrodes were deposited on the ZnO nanorods and annealed in different temperatures to observe the variation of SBH between Au and ZnO. The minimum series resistance and barrier height are observed to be 3.62 x104 Ω and 0.673 eV, respectively for the 450 °C annealed sample.

碩士
逢甲大學
電子工程學系
105
This research mainly investigates of non-vacuum environment, low cost and fast production of Ultrasonic Spray Pyrolysis Deposition technology to fabricate metal-semiconductor-metal structure of MgZnO UV Photodetector, then use of two different electrode Metal, Al and Au to observe the characteristics of devices. In order to know the surface conditions, thickness, chemical composition, roughness, crystal structure, extinction coefficient, and wavelength of the absorbed light of the MgZnO oxide film the (1) Scanning Electron Microscope (SEM) (2) Electron spectroscopy for chemical analysis (ESCA) (3) Atomic force microscopy (AFM) (4) X-ray Diffraction (XRD) (5) Photoluminescence Spectrometer (PL) (6) Ellipsometer (7) UV/Visible/NIR Spectrophotometer. First, the surface and cross-section of the MgZnO film grown by the USPD were observed by scanning electron microscopy, then the ESCA and XRD were used to confirm that the oxide layer was MgZnO. Moreover, the surface roughness of the MgZnO oxide layer is observed by AFM. Finally, three different optical analysis instruments were used to observe the band of the reaction of MgZnO oxide layer by PL, Ellipsometer, UV/Visible/NIR Spectrophotometer. Then we use the current-voltage measurement and spectral measurement to analyze the MgZnO metal - semiconductor - metal UV Photodetector dark current, (Rphoto/dark) and spectral analysis, we found that with the increase of Mg content, dark current from Mg0.1Zn0.9O 3.14×10-5reduced toMg0.6Zn0.4O 3×10-10, then we found Mg0.5Zn0.5O have Rphoto/dark 3.13×103 and 4.01×1012 detection. Finally, from the electrical analysis, spectral response measurement or the optical material analysis of Mg0.1Zn0.9O～Mg0.7Zn0.3O can be seen that the reaction of light from UV-A to UV-C covers all the ultraviolet light Band. So that the USPD grown of MgZnO UV Photodetector which are potential in the industrial applications.

碩士
國立虎尾科技大學
光電與材料科技研究所
99
This study is grown ZnO films of high quality by metal organic chemical vapor deposition on silicon substrates, analysis equipment: X-ray diffraction (XRD), field emission scanning electron microscope ( SEM), Photoluminescence (PL), Hall effect (Hall effect) of the test, the first of the temperature 600 ℃, pressures (1,50,100,150,200 Torr) of ZnO thin film. When the pressure 1Torr, temperatures (500,550,600,650,700 ℃) on ZnO films characteristics were studied. Crystal structure of thin-film appearance, photoluminescence, carrier concentration, mobility analysis, the analysis found that 600 ℃ in temperature when the pressure was fixed at 1Torr ZnO film has a strong (002) peak produce, PL analysis in the UV band and has a good peak production, then the temperature is 600 ℃ different Torr fixed number of zinc oxide thin film after photolithography process, the RF sputtering, then LCR meter measurement components of the UV resistance and capacitance changes produced by the analysis and found that the temperature 600 ℃, pressure 1Torr ZnO films grown under the highest component of variation.

碩士
國立成功大學
微電子工程研究所
104
This thesis employed electroplating technique to deposit an inorganic CuSCN material to replace the conventional PEDOT:PSS and TPD-Si2 organic materials as a hole transport layer for applying to a novel nanocomposite photodetector. To fabricate the photodetector, the CuSCN hole transport layer was covered with a nanocomposite active layer followed by evaporating BCP as a hole block layer, and a sputtered aluminum film as the electrode. The active layer consists of a P-type organic PVK material and a N-type wide band-gap ZnO nanoparticles. When the device under UV illumination and reverse biased condition, the ZnO nanoparticles in the active layer generate electron/hole pairs. The light-generated holes are transported from PVK and CuSCN to the ITO electrode. In the same time, the light-generated electrons are trapped in the ZnO nanoparticles due to lack of a percolation network and the strong quantum confinement effect of the PVK−ZnO NPs composite band structure. The trapped electrons in the ZnO nanocomposite will create a band bending of the polymer which results in a large amount of holes injecting into the device from the top Al contact, thus generates significant amount of additional photo current. The fabricated photodetector can generate a photocurrent of more than two orders of magnitude higher than that of the dark current under a 360 nm 24.9 μW/cm^2 UV illumination, a high UV to visible rejection ratio of 94 times, and high detectivity of 9.12×10^12 Jones. The device’s performance is better than typical conventional inorganic photodetectors. Besides, the nanocomposite device possesses the advantages of flexibility, light weight and lower cost to manufacture. Therefore, the studied UV detector has a great potential to replace the conventional inorganic one for low cost and high performance UV detecting applications.

碩士
逢甲大學
材料科學與工程學系
107
In this study, ZnO-based nanowires arrays were grown on p-GaN thin film by the low-temperature hydrothermal method for fabrication p-n heterojunction ultraviolet (UV) photodetectors. The author reported that comparison of the microstructural festures and photoelectrical properties between ZnO, Ga-doped ZnO (GZO), In-doped ZnO (IZO) and Ga-In co-doped ZnO (GIZO) heterojunction ultraviolet photodetectors. Experiemntal results showed that the UV photodetectors based on GIZO nanowires exhibited the highest photoconductivity gain and sensitivity of 4.24x104 under zero bias. It was demonstrated that the p-type GaN/n-type ZnO nanowire arrays heterojunction self-powered ultraviolet photodetectors were fabricated onto sapphire substrate. 　　In addition, hydrothermally synthesized ZnO-based nanowire arrays were also grown on glass and PET substrates for developing metal-semiconductor-metal (MSM) UV photodetectors. We found that the ZnO-based photodetectors fabricated on glass substrates had better electreical performance than those of photodetectors fabricated on PET substrates. The photodetectors fabricated onto PET bore a compressive strain exhibited better UV response than the devices bore a tensile strain, while the photodetectors bore a tensile strain exhibited good photoresponse than the devices bore a compressive strain. It was found that the GIZO devices had better stability and photocurrents that those of the pure ZnO devices. We successfully fabricated flexible UV photodetectors based on ZnO-based nanowire arrays, which can be widely used in smart technology and automation equipments in the future.

碩士
國立成功大學
微電子工程研究所碩博士班
101
In this study, the ZnO thin film which has high quality and uniformity was grown at low temperature by atomic layer deposition system. The diethylzinc, Bis(cyclopentadienyl) magnesium and water were used as precursors, and then varied the pulse time of precursors and substrate temperature to have low defect and carrier concentration of the ZnO thin film. Moreover, the optical energy bandgap of the MgZnO changed by various doping amounts of magnesium, and applied to the metal-semiconductor- metal ultraviolet photodetector, which cut-off wavelength was lower than 370nm. This study was divided into two parts. At first, to have best quality of ZnO thin film by varied the substrate temperature. According to the window of self-limiting, the substrate temperature from 150℃ to 200℃ were self-limiting in atomic layer deposition system. The ZnO thin film has fastest deposition rate of 1.64Å/cycle and highest electron concentration about 8.27×1019cm-3 at 200℃. However, it has lowest electron concentration of 5.6×1017cm-3 and deposition rate of 1.06Å/cycle lower when the substrate temperature at 100℃. The MgZnO thin film changed the Mg contents by various ratio of ZnO and MgO. In this study, the MgZnO which grown at 100℃ and 350℃ with ratio of 9:1 were applied into metal-semiconductor-metal ultraviolet photodetector. The dark current were 1.72×10-9A and 1.67×10-4A under 5V bias, respectively. The metal-semiconductor-metal ultraviolet photodetector which deposited at 100℃ has lower dark current. Besides, under the light power of 38.02μW and 5V bias at the wavelength of 340nm, the light-dark current ratio and UV-visible rejection ratio (R340/R450) of device were 1.35×103 and 1.38×103, respectively.

碩士
國立中正大學
光機電整合工程研究所
106
In this study, graphene has been attracting great interest due to high carrier mobility and wide absorption wavelength, graphene is a suitable material for photodetector. However, high transmittance and fast carrier recombination brought on photodetector that made by pristine graphene weak photoresponsivity. So we deposited TiO2 thin films with two different sintering method to improve the disadvantages of graphene as a photodetector, in hopes of increasing graphene’s invisible light photoresponsivity via the titanium dioxide. We produce components in two different ways and measure their photoelectric property. From the experimental results, we discover that graphene / atmosphere 400 oC 5 L sintered TiO2 thin film device have the best photoresponsivity. Thus, we use 365 nm LED light source on such device and study the characteristics under different voltage and luminosity, we also use the Xe light as the source to measure the full spectrum photoresponsivity of graphene / sintered 5 L TiO2 device. We discovered that the photoresponsivity are over 200 A / W when the wavelength is within the range of 275 to 385 nm, the maximum photoresponsivity and the maximum specific detectivity were up to 437.15 A / W and 2.31 × 10^13 Jones at the wavelength of 325 nm. The totality of the above result signifies that the graphene / TiO2 photodetector can improve the light absorption and enhanced the optical response of the graphene.

Recently, the fields of energy conversion and storage have drawn great interests in the research community due to the wide range of practical applications in the society. Among them, photodetector (PD) and supercapacitor (SC) have attracted potential imprints for energy conversion and storage applications. This thesis is thus focused on the fabrication of efficient self-powered ultraviolet (UV) PD and SC based on optically and electrochemically active heterostructure materials. Firstly, self-powered UV PD is explored based on one dimensional zinc oxide (ZnO) nanorods (NRs). The charge carrier density of ZnO NRs was modified by doping of halogen elements to enhance the self-powered photo response. Interestingly, 5.5 times enhancement in the photo response of halogen doped ZnO NRs was noticed as compared to pristine ZnO NRs. Further charge carrier modification of ZnO NRs was performed via hydrogenation process of ZnO NRs. Efficient increase in the carrier density of hydrogenated ZnO (H: ZnO) NRs allows enhancing the photo response to nearly 900% and 82% as compared to pristine ZnO NRs and halogen doped ZnO NRs, respectively. The optically as well as electrochemically active heterostructure was then introduced by integrating zinc cobalt oxide (ZnCo2O4) with H: ZnO NRs to form ZnCo2O4/H: ZnO NRs for the applications of UV PD and SC. Further enhancement of 75% in the photo response of ZnCo2O4/H: ZnO NRs was obtained as compared to H: ZnO NRs in self-powered configuration. The photo response behaviour of the ZnCo2O4/H: ZnO NRs PD was investigated under different UV illumination intensities in absence of external bias voltage. A power law dependence of the response of the PD on UV illumination intensity was displayed. Moreover, faster photon detection speed in the order of few milliseconds was also achieved for the self-powered PD. Furthermore, efficient UV detection efficiency for the PD was obtained. The electrochemical performance of the ZnCo2O4/H: ZnO NRs was then investigated in detail. Efficient energy storage performance of ZnCo2O4/H: ZnO NRs was obtained where 63% enhancement in energy storage performance of ZnCo2O4/H: ZnO NRs electrode was observed as compared to ZnCo2O4 alone. For the investigation of energy storage performance of ZnCo2O4/H: ZnO NRs in presence of UV illumination, a solid-state symmetric SC (SSC) was fabricated composed of ZnCo2O4/H: ZnO NRs electrodes. The energy storage performance of the SSC was analysed both in the absence and the presence of UV illumination. An appreciable, 2.7 times enhancement in specific capacitance of the SSC was noticed under UV illumination as compared to the absence of UV. It was found that with the increase in UV illumination intensity, the electrochemical performance of the SSC increases linearly. The capacitance stability of the SSC was further studied for 4000 cycles both in the presence and the absence of UV. Notably, only 2% degradation of the capacitive response of the SSC was noticed under UV illumination as compared to absence of UV. Moreover, 175% enhancement in energy density of the SSC was obtained in presence of UV. To expand the working voltage of the SSC, an asymmetric solid-state SC (ASC) was fabricated composed of ZnCo2O4/H: ZnO NRs as positive electrode and activated carbon (AC) as negative electrode. The working voltage of the ASC is increased from 0.6 to 1.5 V, thus providing an increase in overall energy storage performance of the ASC as compared to SSC. The charge storage mechanism of the ASC was discussed in detail. For the direct practical implementation of the ASC, a PD was fabricated based on ZnCo2O4/H: ZnO NRs as photosensitive material and connected in series configuration with the ASC. As-fabricated ASC can easily offer desired power to the ZnCo2O4/H: ZnO NRs PD during the conversion of optical to electrical signal. Increase in the photo response of the PD was observed in presence of UV illumination. For further expansion of the working voltage of ASC, three ASCs were connected internally in series to form solid-state asymmetric tandem SC (ATSC). The electrochemical response of the ATSC electrodes composed of hybrid reduced graphene oxide (rGO)-carbon nanotubes (CNTs)-ZnCo2O4 (rGO-CNTs-ZnCo2O4) as positive and rGO-CNTs-iron (III) oxide (rGO-CNTs- Fe2O3) negative electrodes were performed systematically. The efficient energy storage performance of the ATSC is due to the synergistic contribution of each of individual nanomaterials in the hybrid electrodes. The working voltage of the ATSC was measured to be 4.5 V which is three times larger than ASC. As a result, a significant increase in energy density (61%) and power density (33%) was noticed as compared to ASC. Moreover, the electrochemical measurement of the ATSC was also studied at different mechanical bending deformation angles ranging from 0 to 60o at a working voltage of 4.5 V. Interestingly, no significant deviation in electrochemical response was observed under the mechanical deformations of the ATSC. In addition, the energy storage performance of the ATSC was measured at different working voltage ranging from 1.5 to 4.5 V. With increase in the working voltage, the energy storage performances (energy density and power density) of the ATSC increase following a linear function. In addition, for the direct practical application, ZnCo2O4/H: ZnO NRs PD was driven by the ATSC used as a power source for the detection of UV light.

碩士
中原大學
電子工程研究所
104
In this study, we grow zinc oxide (ZnO) nanorod array and nanorod film with aputtered ZnO seed layer on sapphire substrates by aqueous solution deposition (ASD) at 50 oC. Characteristics of the ZnO nanorod film will be investigated. The PL analysis of ZnO nanorod film shows the typical emissions of narrow exciton related UV band peak at 376 nm and broad defect related green–yellow (550~650 nm) bands is likely due to oxygen vacancies and the emission is improved after annealing. Inter-digital electrode was evaporated on ZnO nanorod film to fabricate ZnO UV photodetector and measure photorespond. We obtain that the current ratio of photodetector with ZnO nanorod film annealed at 400 oC in N2O is 144.15, the rise time is 2.5 sec, the decay time is 410 sec. We also use Ag for large area electrode to decrease contact resistance, the current ratio is 2538.49, the rise time is 1.5 sec, the decay time is 51.5 sec. We use (NH4)2S to passivate the ZnO film surface. The photorespond decrease because the sulfide left at the interface of ZnO film surface and electrode. We fabricate a Al/ALD-Al2O3/ZnO MOS capacitor and measure the capacitance, the result shows there is a serious interface charge problem.

碩士
國立交通大學
電子工程學系 電子研究所
101
In recent years, the detection of ultraviolet (UV) radiation has attracted extensively interest due to the great decline of the stratospheric ozone layer. Because of its wide band gap, low cost, strong radiation hardness and high thermal and chemical stability, ZnO has become the most promising candidate for UV photodetector. In this thesis, a transparent UV detector was fabricated using nano-heterojunctions (NHJs) composed of p-type NiO and n-type ZnO nanowires. Via DC-magnetron sputtering system, the p-type NiO was deposited onto the vertically-aligned n-type ZnO nanowires which were grown by low-temperature hydrothermal growth process. The as-sputtered NiO on the ZnO nanowires showed the great junction area of the NHJs. Thus, the optoelectronic characteristics were improved. In the beginning of this thesis, the effect of NiO thickness on the optoelectronic characteristics of the UV detector was investigated. It demonstrated that the as-prepared device with 250 nm thick NiO nanostructures showed good sensitivity (IUV/IDark = 4.98 @ -2V) under UV light (365 nm, 0.3 mW/cm2) illumination. However, the device also represented a great photo-response to visible light (IVisible/IDark = 3.82 @ -2V). Hence, in order to suppress the photo-response of the device under visible light illumination, thermal treatments were utilized to reduce the structural defects of ZnO nanowires. It revealed that the p-NiO/ n-ZnO nanowires devices with ZnO nanowires which were annealed in N2 ambience at 500 ℃ for 10 minutes exhibited lower structural defects, lower leakage current, and superior sensitivity (IUV/IDark = 5.65 @ -2V, and IVisible/IDark = 1.35 @ -2V). Moreover, for the propose of reducing the leakage current to further improve the sensitivity of the UV detector, an ultrathin SiO2 layer was deposited by plasma enhanced chemical vapor deposition (PECVD) as interlayer between NiO and ZnO nanowires was proposed in this study. And the dependence of the optoelectronic characteristics on the SiO2 thickness was also discussed. Encouragingly, as the reverse bias 2 V applied, the IUV/IDark increased substantially from 5.65 to 16.21 as the SiO2 thickness increased from 0 to 6 nm. The phenomenon was attributed to the ultrathin SiO2 layer which can not seriously affect the photo-excited high-energy carriers but remarkably depress the dark-state low-energy carriers due to the tunneling mechanism. In this work, the novel UV detector composed of the p-NiO/ insulator-SiO2/ n-ZnO nanowires demonstrated the excellent sensitivity, thermal stability, radiation hardness and repeatable photo-response to UV light, making it promising for the future developments of optoelectronic applications.

博士
國立成功大學
材料科學及工程學系碩博士班
101
In this study, TiO2 films were grown by an atomic layer deposition (ALD) system using TiCl4 and H2O as precursors. The results demonstrate that the ALD system possesses excellent uniformity, high conformity, and accuracy in thickness-control of films due to its unique film-growth mechanism of self-limited surface reaction. The growth rate of TiO2 films grown by ALD is about 0.11 nm/cycle. For crystal structure analysis of ALD-TiO2 films, the results show that the TiO2 film grown at 100 oC has an amorphous structure, whether the film is grown on an Si or FTO-glass substrate. However, when the growth temperatures were above 150 oC, the substrate played an important effect on the crystal growth of ALD-TiO2 films. For using Si as substrate, the TiO2 film has a polycrystalline structure of anatase phase as deposited at 150 – 350 oC, and a polycrystalline structure of anatase mixed with little rutile phase as grown at 400 – 500 oC. For using FTO-glass as substrate, the TiO2 film has a polycrystalline structure of anatase phase as formed at 150 – 250 oC, and a polycrystalline structure of rutile phase obtained at 300 – 500 oC. For crystal growth mechanism of ALD-TiO2 films, there are three types of crystal growth mechanisms proposed in this study. At 150 – 250 oC, the crystal grain size of TiO2 film decreases with increasing growth temperature whether the film grown on the more lattice-matched substrate that is assigned to the “space-limited crystal growth mechanism”. However, the crystal growth mechanism of ALD-TiO2 films grown at 300 – 500 oC demonstrates a substrate-dependence behavior. If the ALD-TiO2 films grown on lattice less matched substrate (such as Si wafer), the TiO2 film exhibits a “conventional crystal growth mechanism” that the crystal grain size of film increases with increasing growth temperature. If the ALD-TiO2 films grown on more lattice-matched substrate (such as FTO-glass), the TiO2 film has an “epitaxial crystal growth mechanism” that the crystal grain size of film is dependent on the crystal grain size of substrate, not relate to growth temperature. In addition, a process for constructing three-dimensional (3D) nanostructure consisting of TiO2 spheres on an ITO-glass substrate with easy and accurate shell-thickness controlled by a template-assisted ALD is reported in this study. Furthermore, in order to measure the absorbance spectrum for a nanostructure accurately a modified measurement method is suggested that is A% ＝ 100% － T% － R% (where the A%, T%, and R% are absorbance, transmittance and reflectance, respectively). Besides, a novel ultraviolet photodetector (UV-PD) based on TiO2/water solid-liquid heterojunction (SLHJ) is also reported in this study. The SLHJ UV-PD exhibits a high photosensitivity, excellent spectral selectivity, linear variation in photocurrent, and fast response that the device is operated without any external bias. Using a TiO2 film grown by ALD as the active layer of SLHJ UV-PD, the device has a maximum responsivity of 69 mA/W. The SLHJ UV-PD has an exceptional competence for UV-light detection that presents a promising direction for future development of commercially low-cost photodetectors.

碩士
國立交通大學
光電工程系所
95
In this thesis, we constructed a two-terminal metal-oxide-semiconductor photodetector for which light is absorbed in a capping layer of silicon nanocrystals embedded in a mesoporous silica matrix on p-type silicon substrates. Operated at reverse bias, enhanced photoresponse from 340 to 1000 nm was observed. The highest optoelectronic conversion efficiency is as high as 138%. The enhancements were explained by a transistorlike mechanism, in which the inversion layer acts as the emitter and trapped positive charges in the mesoporous dielectric layer assist carrier injection from the inversion layer to the contact, such that the primary photocurrent could be amplified.

Visible-blind and solar-blind ultraviolet photodetectors based on GaN/AlGaN were designed, fabricated, and characterized for commercial and military applications. High performance back-illuminated solar-blind MSM achieved external quantum efficiency of ~48%. The dark current of 40x40μm MSM was less than the instrument measurement limitation of 20fA for a bias <100V. No photoconductive gain was observed. With an n-type doped high-Al ratio "window" Al₀.₆Ga₀.₄N layer, back-illuminated solar-blind p-i-n photodiode achieved a quantum efficiency of ~55% at zero-bias. Absorption edge study of both MSM and p-i-n photodetectors, based on device spectral responses, resulted in a performance comparison of MSMs and p-i-ns, as the solar-blind photodetection requires a sharp solar-blind rejection. Photoconductive detectors and avalanche photodetectors, with the internal gain advantage, have been discussed as well. A 30μm diameter GaN avalanche photodiode achieved a gain >23, with a dark current less than 100pA. The breakdown showed a positive temperature coefficient of 0.03 V/K that is characteristic of avalanche breakdown. SiC APDs, as candidates for visible-blind applications, have been designed, fabricated and characterized. An avalanche gain higher than 10⁵, with a dark current less than 1nA, showed the potential of SiC APD replacing PMTs for high sensitivity visible-blind UV detection. A silicon-based optical receiver has been presented in the Appendix. With the photodiode internal avalanche gain ~4, a sensitivity ~-6.9dBm at 10Gbps has been achieved.
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碩士
國立成功大學
微電子工程研究所
102
The research mainly investigates on the improvement of AlGaN/GaN Schottky-based ultraviolet (UV) photodetectors (PDs) by using oxidation techniques. Among several oxidation methods, we choose two non-vacuum and low cost approaches to fabricate the oxide layer. One is the hydrogen peroxide (H2O2) oxidation technique, and the other one is ultrasonic spray pyrolysis deposition (USPD). Furthermore, these two oxidation techniques are applied to three different Schottky-based UV PDs including metal-semiconductor-metal (MSM), Schottky barrier (SB), and metal- insulator-semiconductor (MIS) structures. In order to know oxide thickness, chemical composition, surface roughness, refractive index, and transmittance of the oxide layer, the (1) Transmission Electron Microscopy (TEM) (2) Electron Spectroscopy for Chemical Analysis (ESCA) (3) Atomic Force Microscopy (AFM), (4) Ellipsometry, and (5) UV/VIS/NIR spectrophotometer are adopted in this research. TEM is used to confirm the oxide thickness formed by two oxidation techniques. ESCA and the quantitative analysis are employed to confirm the Al2O3 oxide layer. Moreover, the surface roughness of the oxide layer is observed by AFM. The ellipsometry and UV/VIS/NIR spectrophotometer are operated to analyze the refractive index and the transmittance of the oxide layer. After the material analysis of oxide layer, H2O2 oxidation technique was applied to (1) MSM and (2) SB UV PDs to form the passivation layer. Compared with MSM UV PD without H2O2 passivation, it was found that the dark current of MSM UV PD with H2O2 passivation was decreased by 10 times and the photocurrent was enhanced. Furthermore, the UV to visible rejection ratio (RUV/VIS) was increased from 20 to 2.11×103. In the low frequency noise measurement, the noise current was reduced so that the noise equivalent power was lowered. Moreover, the detectivity of UV PD was improved by 44 times. In addition, the performances of SB UV PD with H2O2 passivation were investigated. It was found that the dark current was reduced by 102 times and the photocurrent was increased compared to the SB UV PD without H2O2 passivation. Furthermore, the RUV/VIS was improved from 39 to 2.47×103. Moreover, the detectivity was enhanced by 107 times. Additionally, the H2O2 oxidation technique and USPD were employed to form the Al2O3 as the insulator layer and then applied to MIS UV PDs. Firstly, we conducted experiments with different H2O2 treatment time to find the optimization of MIS UV PDs. According to the experimental results, it was found that using H2O2 treatment for 5 minutes could make the devices optimized. Compared with SB UV PD without H2O2 passivation, the dark current was suppressed by 103 times, and the RUV/VIS was increased from 39 to 7.46×104. Moreover, the detectivity was improved by 102 times. Furthermore, the oxide layer formed by USPD was employed to fabricate the MIS UV PDs. In the experiments, it was observed that the optimization of MIS UV PDs by USPD was obtained by depositing 15nm Al2O3. Compared with SB UV PD without H2O2 passivation, the dark current was decreased by 103 times. Moreover, the RUV/VIS was enhanced by 104 times and the detectivity was increased by 103 times. For the purpose of investigating the thermal stability of UV PDs, the temperature-dependent measurement was used to observe the characteristics. The operating temperature was set at 300K, 360K, 420K, and 480K. Based on the experimental results, it was found that MSM UV PDs were capable of working at 420K. Furthermore, the SB and MIS UV PDs were able to be operated at 480K. In this dissertation, we successfully applied two oxidation techniques to three different structures of Schottky-based UV PDs. According to the experimental results and analysis, these two oxidation techniques are both effective for improving the characteristics of UV PDs. These two oxidation techniques are non-vacuum and low cost fabrication methods which are potential in the industrial applications.