Abstract—A dependency of quantum efficiency of nn+pp+ silicon complementary metal–oxide–semiconductor integrated lightemitting devices on the current density through the active device areas is demonstrated. It was observed that an increase in current density from 1 6 10+2 to 2 2 10+4 A cm 2 through the active regions of silicon n+pp+ light-emitting diodes results in an increase in the external quantum efficiency from 1 6 10 7 to 5 8 10 6 (approximately two orders of magnitude). The light intensity correspondingly increase from 10 6 to 10 1 W cm 2 mA (approximately five orders of magnitude). In our study, the highest efficiency device operate in the p-n junction reverse bias avalanche mode and utilize current density increase by means of vertical and lateral electrical field confinement at a wedge-shaped n+ tip placed in a region of lower doping density and opposite highly conductive p+ regions.

Implementation of a control system for an active camouflage system based on thermal elements and LED technology.

2008年以來，發光二極體(Light Emitting Diode, LED)照明已儼然成為大部分國家積極推展的新光源，蔚為未來照明市場主流相當明確。各大廠莫不加速步伐，積極切入爭取市場需求，期望在此新興高速成長市場上，有決定性的開始。但也因產業鏈上的巨大變化，如何在價值鏈上找出自己的定位，執行何種營運模式，做出差異化，成為勝敗關鍵之ㄧ。 個案公司為台灣LED產業之代表性企業，在台灣LED照明的發展也具指標性意義。本研究就以個案公司為研究對象，經由訪談及資料蒐集，做內外的競爭生態和價值鏈上的分析，再用五力模型探討個案公司在價值鏈上的競合模型與策略發展。 經過研究結果顯示，因LED照明產業廠家數目倍增，使得既有廠商直接競爭激烈，個案公司在客戶關係、核心競爭力，以及供應商結構，皆有相當的開發優勢，個案公司避免流於一般在供應鏈上的營運模式，結合其既有的核心競爭力和合作夥伴，定義需要的競合模型及策略步驟，順利踏入對其為新領域的照明產業，並成功的踏出第一步。 LED照明產業在高投資環境，高競爭態勢，專利及新應用上的限制，除了在產品技術上和成本控管上之競爭力，如能在價值鏈上如何做出應有的價值定位，配合發展策略，使其生意模式在價值鏈上產生差異化，擴大上中下游合作機會，甚至轉競爭為合作，共同擴大出海口，更是創造營收與利潤的決勝關鍵。

Submitted by Hiolanda Rêgo (hiolandar@gmail.com) on 2013-05-06T19:04:29Z No. of bitstreams: 1 Dissertação_ODONTO_ Gardênia Paraguassú.pdf: 5642146 bytes, checksum: 2008162ae377984ab098ded644cdb235 (MD5) / Approved for entry into archive by Flávia Ferreira(flaviaccf@yahoo.com.br) on 2013-05-07T19:23:06Z (GMT) No. of bitstreams: 1 Dissertação_ODONTO_ Gardênia Paraguassú.pdf: 5642146 bytes, checksum: 2008162ae377984ab098ded644cdb235 (MD5) / Made available in DSpace on 2013-05-07T19:23:06Z (GMT). No. of bitstreams: 1 Dissertação_ODONTO_ Gardênia Paraguassú.pdf: 5642146 bytes, checksum: 2008162ae377984ab098ded644cdb235 (MD5) / FASPESB; CNPQ / A deficiência de hormônio tireoidiano tem sido associada a distúrbios no metabolismo corporal, incluindo o processo de cicatrização de feridas. Alternativas terapêuticas como as fototerapias Laser e LED têm evidenciado resultados positivos no reparo tecidual, mas a sua associação a distúrbios metabólicos como o hipotireoidismo não tem sido observada na literatura. Este estudo avaliou, através da análise histológica e imuno-histoquímica, a influência das fototerapias Laser e LED no processo de cicatrização de feridas excisionais em ratos hipotireoidianos e eutireoidianos. Para tanto, 72 ratos Wistar albinus machos foram aleatoriamente distribuídos em dois grupos (Eutireoidiano e Hipotireoidiano) com 36 animais cada, e estes subdivididos em 3 subgrupos: Grupos controles Eutireoidiano (EC) e Hipotireoidiano (HC), nos quais não foi realizado nenhum tipo de tratamento; Grupos Laser Eutireoidiano (EL) e Hipotireoidiano (HL), irradiados com luz Laser (GaAlAs, 660nm, 40mW, CW, 0,04cm², 24J/cm2 por sessão, Twin Flex Evolution ®, MMoptics) e Grupos LED Eutireoidiano (ED) e Hipotireoidiano (HD), cujas feridas foram irradiadas com luz LED (InGaAlP, λ630±20nm, 150mW, CW, 0,5cm², 24J/cm² por sessão, FisioLED®, MMoptics). Feridas cirúrgicas padronizadas (1cm2) foram confeccionadas no dorso dos animais e submetidas à irradiação imediatamente após o procedimento cirúrgico, sendo repetidas a cada 48 horas, até a morte dos animais (sete e 14 dias). Os espécimes foram processados usando as técnicas de coloração HE e Picrosírius, e técnica imuno-histoquímica para avaliação de colágeno I e III, e avaliados por microscópica óptica. Os dados foram estatisticamente analisados. Os resultados demonstraram que nos grupos não irradiados, o hipotireoidismo dificultou a repavimentação epitelial (Exato de Fisher, p<0,05). Os grupos irradiados com Laser ou LED apresentaram melhores resultados quando comparados aos grupos não irradiados, sendo as variáveis reepitelização, proliferação fibroblástica, distribuição colagênica e imunoexpressão dos colágenos tipo I e III, as que mostraram diferenças estatísticas mais marcantes (Exato de Fisher, p<0,05). De modo geral, dentro dos parâmetros utilizados, as fototerapias Laser e LED foram capazes de melhorar o processo cicatricial, nestes animais. / Salvador

In this work, we propose a model to address the challenge of droop in internal quantum efficiency in InGaN/GaN Multiple Quantum Well LEDs. Efficiency droop limits the performance of high brightness LEDs as they operate at currents greater than 350mA. The efficiency droop is a multi-physics problem posed by various entities such as (1) dislocation recombination, (2) Auger recombination in active region, (3) non-radiative recombination, and (4) current overflow in the active region. This work aims at reducing the droop associated with non-radiative recombination by engineering the quantum well barrier thickness and materials. The goals are three-fold, namely: (1) To explore the role of barriers in determining the droop in internal quantum efficiency and to justify the use of multiple barriers to increase the carrier density and reduce the leakage current thereby increase the radiative recombination at higher current densities ; (2) Propose optimum barrier specifications such as number, material combination, and thickness for downscaling the efficiency droop, and thereby improving the device efficiency; and (3) Finally, obtain improved efficiency by engineering the barrier in a realistically-sized device by considering the effects of long-range strain fields in the device.

The thesis aims to analyze the current situation regarding the marketing mix in the selected company. Based on this analysis it was found that the current marketing mix should be adjusted in an attempt to increase sales and brand awareness. It was suggested solutions to improve the situation, which consists of improvement proposals. These proposals focus according to the results of the SWOT analysis to improve brand image and expand its presence among the customers. It is also trying to solve the problem with the purchasing power of customers, not least the problem of obtaining customers. Two selected suggestions, which attempts to solve the problem of obtaining customers and also partly to raise awareness about the company and its operations were subsequently tested market.

No description available.

No description available.

UV and deep-UV emitters based on AlGaN/AlN heterostructures are very inefficient due to the high lattice mismatch of these films with sapphire substrates, leading to high dislocation densities. This thesis describes the characterisation of the nanostructures of a range of UV structures, including c-plane (polar) AlGaN epilayers grown on AlN template, and nonpolar GaN/AlGaN MQWs grown on a-plane GaN template. The results are based primarily on transmission electron microscopy (TEM), cathodoluminescence in the scanning electron microscope (SEM-CL), high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) measurements. The structural and optical properties of various types of defect were examined in the c-plane AlGaN epilayers. Strain analysis based on in-situ wafer curvature measurements was employed to describe the strain relief mechanisms for different AlGaN compositions and to correlate the strain to each type of defect observed in the epilayers. This is followed by the investigation of AlN template growth optimisation, based on the TMA pre-dose on sapphire method to enhance the quality and the surface morphology of the template further. The initial growth conditions were shown to be critical for the final AlN film morphology. A higher TMA pre-dose has been shown to enable a better Al coverage leading to a fully coalesced AlN film at 1 μm thickness. An atomically smooth surface of the template was achieved over a large 10 x 10 μm AFM scale. Finally, the investigation of UV emitters based on nonpolar crystal orientations is presented. The SiNx interlayer was able to reduce the threading dislocation density but was also found to generate voids with longer SiNx growth time. The relationship between voids, threading dislocations, inversion domain boundaries and their associated V-defects and the variation in MQW growth rate has been discussed in detail.

Ultraviolet (UV) group III-Nitride-based light emitters have been used in various applications such as water purification, medicine, lighting and chemical detection. Despite attractive properties such as bandgap tunability in the whole UV range (UV-C to UV-A), high chemical stability and relative low cost, the low quantum efficiency hamper the full utilization. In fact, external quantum efficiencies of UV devices are below 10 % for emission wavelength shorter than 350 nm. This thesis aims to show alternative solutions to such problems by employing nanowires (NWs) structures, and target the eventual application of reliable and high power NWs-based light-emitting devices, enabling large-scale production using the established silicon foundry processes. Here, we present the improvement of injection current and optical power of AlGaN NWs LEDs by involving a metal bilayer thin film with a dual purpose: eliminate the potential barrier for carrier transport, and inhibit the formation of silicide. We then study the AlGaN/GaN UV LED design to optimize the device structure and improve the LED performance. We compared multiple devices having different active region and graded layers’ thicknesses. Improvement on the output power was achieved for larger p-AlGaN graded layer and thinner p-GaN contact layer structure due to the better hole injection and lower p-GaN absorption. The junction temperature of AlGaN-based NWs LEDs on metal bi-layer and silicon is also presented as a crucial parameter affecting the device efficiency, chromaticity and reliability. In this regard, by using the forward-voltage and peak-shift method we extracted the junction temperature values and confirmed the better heat dissipation in NWs grown on metal substrate. Finally, the origin of single and ensemble NWs current injection and injection efficiency are studied by treating the AlGaN NWs with KOH solution. Measurements based on conductive atomic force microscopy enabled a fast feedback cycle without fabricating the device. Despite the NWs technology is still at its infancy compared to the matured planar, we believe that this research effort will give important insight in advancing the AlGaN NWs devices for future industrial employment.