It is the objective of this work to focus on heat dissipation in gallium nitride based solid-state logic devices as well as optoelectronic devices, a major technical challenge. With a direct band gap that is tunable through alloying between 0.7-3.8 eV, this material provides an enabling technology for power generation, telecommunications, power electronics, and advanced lighting sources. Previously, advances in these areas were limited by the availability of high quality material and growth methods, resulting in high dislocation densities and impurities. Within the last 40 years improvements in epitaxial growth methods such as lateral epitaxial overgrowth (LEO), hydride vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), and metal organic chemical vapor deposition (MOCVD), has enabled electron mobilities greater than 1600 cm2V/s, with dislocation densities less than 109/cm2. Increases in device performance with improved materials have now been associated with an increase in power dissipation (>1kW/cm2) that is limiting further development. In the following work thermophysical material of III-V semiconducting thin films and associated substrates are presented. Numerical modeling coupled with optical (micro-IR imaging and micro-Raman Spectroscopy) methods was utilized in order to study the heat carrier motion and the temperature distribution in an operating device. Results from temperature mapping experiments led to an analysis for design of next generation advancements in electronics packaging.

In the study, conductive distributed Bragg reflectors (DBRs) fabricated at room temperature based on porous indium tin oxide (ITO) on dense ITO bilayers were proposed for resonant cavity organic light emitting diodes (RCOLEDs). In the fabrication of the ITO DBRs, the low refractive index porous ITO films were obtained by applying supercritical CO2 treatment at different temperature and pressures on the spin-coated sol-gel ITO films. On the other hand, the high refractive index ITO films were grown at room temperature by long-throw reactive ratio-frequency magnetron sputtering. The refractive index of the porous ITO film and ITO films were 1.54 and 2.0, respectively. For the DBR with 4 pairs ITO bilayers, the optical reflectance of more than 70 % was achieved. The stop band and the average resistivity is 140 nm and 2.2¡Ñ10-3 £[-cm, respectively. Finally, electrical and optical characteristics of the RCOLEDs fabricated on the ITO DBR were investigated and compared with those of the conventional OLEDs. The maximum luminous efficiency of 3.79 cd/A was obtained at 347 mA/cm2 for the RCOLED. This luminous efficiency was 26 % higher than that of the conventional OLED.

Luminescent emission of non-fully conjugated homopolymers was successfully demonstrated as light emitting diodes (LEDs) in this research. Coil-like heterocyclic aromatic poly[2,2-(2,5-dialkyloxyphenylene)-4-4¡¦-hexafluoroisopropanebibenzoxazo- les] (6F-PBO-CnOTpA, with n = 10, 15, and 20) was synthesized, and polymer composites of 6F-PBO-CnOTpA was in-situ synthesized with acidified multi-wall carbon nanotube (MWNT- COOH). The non-fully conjugated coil-like heterocyclic aromatic homopolymer was synthesized by reacting 2,2,bis-(3-amino-4-hydroxy[henyl]-hexafluoropropane with 2,5-dialkyloxyterephthalic acid (CnOTpA) for 6F-PBO-CnOTpA, with n = 10, 15, and 20. In addition, MWNT was acidified for connecting the carboxylic group (-COOH) to reduce its aspect ratio and entropy induced aggregation. MWNT-COOH was analyzed using elemental analysis (EA) and viscometry to validate the effects of acidification period. The EA result seemed to suggest that the oxygen content increased, and the carbon and the hydrogen contents decreased with acidification period. The inherent viscosity (£binh) decreased according to acidification period suggesting that the aspect ratio was indeed decreased. A hole transport layer of PEDOT¡GPSS was applied for multi-layer LEDs,. The LEDs all showed a threshold voltage about 4 V also for the composites of 6F-PBO-CnOTpA in-situ polymerized with MWNT-COOH. The 6F-PBO-CnOTpA LEDs with and without MWNT-COOH showed an electroluminescence emission range of 400 to 750 nm.

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.

Optical beam induced current (OBIC) mapping has found wide-spread applications in characterizing semiconductor devices and integrated circuitry. In this study, we have used a two-photon scanning microscope to investigate InGaN light emitting diodes (LED). The defects induced by electrostatic discharge (ESD) can be clearly identified by DC-OBIC images. Additionally, we have combined an E-O modulator and a high frequency phase sensitive lock-in amplifier to conduct time-resolved study on the dynamical properties of the LEDs. The defects also exhibit different delay time when compared with the normal parts.

Recently, as a result of people around the world to actively encourage the creation of new businesses, so that the field of entrepreneurship research has become a field of study of foreign enterprises, the fastest growing part. In particular, Taiwan is now suffering because of the financial turmoil triggered by the economic recession crisis, global competition and rapidly changing industrial structure, but also to the urgent need to develop new industries to provide more employment opportunities. And as a result of the rise of emerging markets, a substantial increase in demand for the material, particularly in the industrial development of the oil must be used is in great demand, resulting in global crude oil stocks continued to decline. In addition, the sharp increase in carbon dioxide emissions, causing global warming, the greenhouse effect serious environmental problems are also plaguing the world, it is "the United Nations Framework Convention on Climate Change's Kyoto Protocol," signed. Under the influence of many factors in the world are looking into the use of resources in alternative energy and energy-efficient power-saving environmental protection products, including solar industry and light-emitting diode (LED) industry the most popular, so many of the new company set up R & D and production of related products. In this study, the production of LED Wafer and Chip professional manufacturer G company for the study, using SWOT Analysis, Five Forces analysis, expert interviews as research methods, analysis of LED current industry conditions and to explore the company's first business process and key success factors, and then find out the case, how can manufacturers in the highly competitive environment, the establishment of a unique business advantage to the follow-up for people wishing to enter the LED reference industrial companies. The case study found that the G company success and have the following six key factors: (1) business and industry pre-market assessment of the right; (2) a clear position; (3) product differentiation (niche products); (4) has a strong start-up team; (5) personality traits entrepreneurs; (6) of prudent financial control, and the scholars referred to the key factors of success in good agreement, therefore, present or future intention to enter the LED after industry into the role of manufacturers with a reference indicator .

Light-emitting diodes (LED) illumination takes considerable applications in nowadays daily lives due to the improvement on efficiency of the LED modules. The connections between the reliability and the lifetime, power efficiency, optical spectrum, and structure design of the LED modules are the major research topics. In this study, high-power LED modules encapsulated with different lens shapes after a thermal-aging test were studied experimentally and numerically. The results showed that the LED modules encapsulated with a hemispherical-shaped plastic lens exhibited a better lifetime due to their better thermal dissipation than those with cylindrical- or elliptical-shaped plastic lenses. In the case of 80¢J aging test, the lifetime of hemispherical-shaped lens was 1.5 times better than the cylindrical- or elliptical-shaped lenses. Decay of radiation pattern and optical spectrum of high-power LED modules fabricated by different manufacturers after a thermal-aging test were investigated experimentally and numerically. The results showed that the radiation pattern of the LED modules at the two view angles of ¡Ó (15o~75o) decreased more than the other angles as aging time increased. Due to the degradation of lens material after thermal aging, the center wavelength of the LED spectrum shifted 5 nm. Furthermore, the radius curvature of plastic lens was observed 6-70 £gm contraction as aging times increased. Both experimental and simulated results clearly indicated that improving the lens structure and lens material is essential to extend the operating life of the high-power LED modules. High-power phosphor-converted white-light-emitting diodes (PC-LEDs) with selected concentration and thickness of Ce:YAG phosphor-doped silicones were investigated to study the thermal degradation effect of the Ce:YAG phosphor-silicone layer. The experimental results showed that the lumen loss, chromaticity (CIE shift), and spectrum intensity reduction increased as the concentration of Ce:YAG phosphor doped silicone increased. We showed that 94% lumen loss was attributed to 5.5 wt% Ce:YAG doping and only 6% of the lumen loss was due to a 1mm thickness of silicone degradation. From practical points of view, we found that a lower doping concentration of the Ce:YAG phosphor in thin silicone is a better choice in terms of having less thermal degradation for use in packaging of the high-power PC-LEDs modules and is essential to extend the operating lifetime of the phosphor-based white LED modules.

This thesis describes the development of III-Nitride materials for light emitting applications. The goals of this research were to create and optimize a green light emitting diode (LED) and laser diode (LD). Metalorganic chemical vapor deposition (MOCVD) was the technique used to grow the epitaxial structures for these devices. The active regions of III-Nitride based LEDs are composed of InₓGa₁₋ₓN, the bandgap of which can be tuned to attain the desired wavelength depending on the percent composition of Indium. An issue with this design is that the optimal growth temperature of InGaN is lower than that of GaN, making the growth temperature of the top p-layers critical to the device performance. Thus, an InGaN:Mg layer was used as the hole injection and p-contact layers for a green led, which can be grown at a lower temperature than GaN:Mg in order to maintain the integrity of the active region. However, the use of InGaN comes with its own set of drawbacks, specifically the formation of V-defects. Several methods were investigated to suppress these defects such as graded p-layers, short period supper lattices, and native GaN substrates. As a result, LEDs emitting at ~532 nm were realized. The epitaxial structure for a III-Nitride LD is more complicated than that of an LED, and so it faces many of the same technical challenges and then some. Strain engineering and defect reduction were the primary focuses of optimization in this study. Superlattice based cladding layers, native GaN substrates, InGaN waveguides, and doping optimization were all utilized to lower the probability of defect formation. This thesis reports on the realization of a 454 nm LD, with higher wavelength devices to follow the same developmental path.

Conducting metallopolymers have been investigated for a variety of applications due to their ability to take advantage of both the mechanical processability of the polymer material, as well as the optical and electronic properties of the metal. Our project goal is to design, synthesize and characterize novel iridium(III)-containing conducting metallopolymers for use as the active layer in polymer light-emitting diodes. We have utilized thiophene functionalized ligands that can be readily electropolymerized into conducting polymer thin films and can be easily incorporated into a device structure. Iridium(III) was chosen as the metal center due to its promising photophysical properties, as similar complexes have demonstrated high luminescent quantum yields and short phosphorescent lifetimes. The coordination environment around the metal can be altered synthetically to tune the emission wavelength across the visible spectrum. The synthetic control over the polymer backbone, as well as the iridium(III) ligand environment, allowed us to independently vary each component, which has provided a variety of materials. The materials are characterized through 1H and 13C NMR, mass spectrometry, elemental analysis, electrochemistry, X-Ray diffraction and X-Ray Photoelectron Spectroscopy. The photophysical properties of the materials are studied through UVvii Visible absorption spectroscopy, UV-Vis-NIR spectroelectrochemistry and steadystate/ time-resolved emission spectroscopy. / text

Solution deposition of thin film photovoltaic materials leads to large variations in the morphological and chemical compositions of the film. In order to improve device functionality, it is important to understand how morphology and chemical composition affects charge generation, separation, and collection. This PhD work will first study bulk methods in order to characterize materials in solution and films. The results are then correlated with microscopy studies examining morphology. Other methods used in this PhD work will directly couple spectra and microscopy. Microscopic regions of such films and devices can be illuminated using scanning confocal microscopy or near-field scanning optical microscopy (NSOM), which allows for one to directly probe regions of the film at or below the optical diffraction limit. By scanning the sample over a fixed laser spot we can simultaneously create image maps of the topographical, electrical and optical properties. This technique, known as laser beam induced current (LBIC) allows one to directly probe a local area of a device with 100-300nm resolution. Along with bulk device efficiency studies, near field and confocal data of inorganic and organic materials are investigated. These include devices fabricated with a blend of P3HT (poly[3-hexylthiophene]) and perylene diimide derivatives, and Cu(InxGa1-x)Se2 [CIGS] nanoparticle devices. Finally, we use a new device architecture, a lateral organic photovoltaic (LOPV) in order to spatially resolve transport in functional organic devices. / text