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Dispositivos fotovoltaicos híbridos baseados em polímeros conjugados e semicondutores inorgânicos estão sendo utilizados nos últimos anos para a produção de células de energia solar com baixo custo. Para que haja uma alta eficiência é necessária dissociação eficiente de éxcitons, por isso é importante conhecer os níveis de energias dos componentes do dispositivo fotovoltaico. O presente estudos mostra que o sistema híbrido formado por nanofios cilíndricos preparados com heteroestrutura radial de camadas alternadas de GaAs/AlGaAs/GaAs recobertas com polímero conjugado poli-fenileno vinileno (PPV) forma uma opção alternativa para a fabricação de dispositivos fotovoltaicos. Os nanofios foram fabricados por Epitaxia por Feixe Molecular (MBE). Tanto potencial interno radial e modulação energética axial produzem a separação eficiente de elétrons e buracos fotoexcitados, que gera emissões de natureza e origem distintas e singulares nos nanofios: emissões envolvendo a impurezas aceitadoras no centro do núcleo de GaAs, bem como éxcitons indiretos presos a interface WZ e BZ e a interface da barreira estreita de AlGaAs na casca do nanofio. Medidas do decaimento temporal da emissão mostram uma forte dependência tempo de vida com o comprimento de onda, o que está associado com o afunilamento e distribuição energética destes estados emissivos. Medidas da emissão com a temperatura dão forte evidencia experimental de que a energia de ligação das impurezas tem uma forte dependência na direção radial. Este sistema híbrido funciona como coletor eficaz de luz tanto no visível quanto no infravermelho próximo. O trabalho demonstra também por espectroscopia resolvida no tempo que éxcitons são dissociados nas interfaces formadas por filmes ultrafinos de polímeros conjugados e nanofios e que esse material à base de arseneto de gálio (GaAs) atua como um forte receptor e separador de elétrons (alta afinidade eletrônica). / Hybrid photovoltaic devices based on conjugated polymers and inorganic semiconductors are being used in recent years to the production of solar cells at low cost. So there is a high efficiency is required efficient exciton dissociation, so it´s important to know the levels of energy of the components of the photovoltaic device. The present studies show that the hybrid system formed by cylindrical radial heterostructure nanowires prepared from alternating layers of GaAs / AlGaAs / GaAs covered with the conjugated polymer poly-phenylene vinylene (PPV) forms an alternative option for the manufacture of photovoltaic devices. Nanowires were manufactured by Molecular Beam Epitaxy (MBE). Both radial and axial inner potential energy modulation produce the efficient separation of electrons and photoexcited holes, which generates distinct and unique nature and source emissions in nanowires: emissions involving the acceptor impurities in the center core of GaAs and indirect excitons attached to the interface WZ and BZ and narrow barrier interface of AlGaAs on the shell of the nanowire. Measures the time decay of the issue show a strong dependence lifetime with the wavelength, which is associated with the bottleneck and energy distribution of emissive states. Emission measurements with temperature provide strong experimental evidence that the impurity binding energy has a strong dependence on the radial direction. This hybrid system works as an efficient collector of light both in the visible and near infrared. The work also shows for time resolved spectroscopy that excitons are dissociated at the interfaces formed by ultrathin conjugated polymers and films and nanowires that this material based on gallium arsenide (GaAs) acts as a strong receiver and electrons separator (high electron affinity ).

The need of the everyday user to transfer large amounts of data is driving the need for larger data transfer capacity. Optical communication networks can satisfy this need. To be economically viable, optical transceivers must be integrated onto chips at low cost, using relatively cheap semiconductor processes. The optical preamplifier (transimpedance amplifier) receives optical information and converts it to a useful electrical form. It must operate at high speed, contribute little distortion to the input signal, and add little electrical noise to the incoming signal. This thesis investigates the design techniques in the literature, and proposes new architectures. Two high performance preamplifiers are designed, one using GaAs HEMTs, and the other using GaAs HBTs, each with different circuit techniques. The HEMT preamplifier has a transimpedance gain of 1.4 kΩ, the highest in the literature for 10 Gb/s operation, along with a low input referred noise current of about 15 pA/Hz1/2 at a bandwidth of 6.3 GHz. The HBT preamplifier also has a transimpedance gain of 1.5 kΩ, with a low input referred noise current of about 7 pA/Hz1/2. Both have clear, open eye-diagrams with a 10 Gb/s bit stream input, and are suitable for integration on a chip. The HEMT preamplifier was implemented as a common-gate, common-source amplifier cascade with a darlington output driver for a 50 Ω load. The HBT preamplifier was implemented as common-emitter darlington amplifier with shunt peaking, and a simple emitter degenerated output driver for a 50 Ω load. Both implementations exceeded the bandwidth, transimpedance gain and noise performance typically expected of the transistor technologies used. It is shown that the transimpedance limit can be circumvented by the use of novel architectures and shunt peaking.

砷化鎵基板對大多數人而言，是陌生的半導體材料，但隨著智慧型手機(Smartphone)及發光二極體(Light Emitting Diode)的普及，砷化鎵已悄悄地來到大家身邊，舉凡智慧型手機的功率放大器，3C產品的LED背光源，LED街道交通號誌，LED汽車車燈，甚至紅外線遙控器電子元件，都是使用砷化鎵作為半導體材料而開發出來的。 根據產業研究報告，砷化鎵基板在行動通訊需求成長及LED滲透率提高的帶動下，2012年至2017年的年複合成長率將以每年11%向上攀升，2017年總產值達到6.5億美元，市場成長可期。個案S公司是砷化鎵基板領導生產商，市場佔有率40%，品質穩定，技術領先其他競爭對手，但近年來新進入市場的砷化鎵基板生產商採用低價策略搶攻市場，使得S公司成長受限，市場領導地位岌岌可危。 本研究是以S公司為例，比較S公司在四元LED市場環境中，與主要競爭對手C公司、A公司的策略差異，首先運用五力分析，分析四元LED市場五種力量的差異，接著以核心競爭力模型，識別出S公司的核心競爭力；用價值鏈模型，說明S公司的價值活動，最後，以策略行銷4C架構，分析比較S公司與C公司、A公司的外顯單位效益成本及內隱交換成本，找出S公司在行銷策略犯的錯誤，建議S公司重新區隔市場，瞄準目標客戶，規劃出S公司定位，提出S公司4P行銷策略-產品策略: 維持供應台灣及中國大陸的砷化鎵基板生產線，不可因為中國大陸生產成本低，就關閉台灣產線，移往中國大陸。定價策略: 追隨競爭者定價策略，迫使C公司與S公司競爭內隱交換成本。通路策略: 保持現有的通路，繼續由台灣當地子公司銷售產品給台灣四元LED磊晶廠。推廣策略: 降價以降低外顯單位效益成本；免費提供測試樣品，降低資訊搜尋成本；運用月暈效應及提供賠償保證，降低道德危機成本；設法要求四元LED磊晶廠更改磊晶機台參數設定，以及為四元LED磊晶廠介紹客戶，建立專屬資產。

Semiconductor band-gap energy can be measured by using photoreflectance (PR) spectroscopy. It used a pump-beam and a probe-beam and measure modulated reflectance (DR) of the probe-beam by chopping on and off the pump-beam. The photon-energy of the pump-beam has to be greater than the band-gap energy of the sample so that electron-hole pair can be produced in the sample. The electron-hole pairs are separated by built-in electric field (Fbi) of the sample and thus reduce strength of Fbi. In this work the Hg lamp was used for the pump beam to observe E_1 and E_1+∆E_1 transitions of GaAs, and its photon energy is greater than E_1 and E_1+∆E_1 bandgaps. We also used the purple, green and red laser to observe GaAs, and their photon energy are greater than E_0 but smaller than E_1gaps. Finally, we will compare the amplitude of the PR spectra with the strength of the Fbi reduced by the pump-beam.

We discove the decrement,comparing the Electroreflectance spectroscopy of theforward biased voltage is 0.5V after the photon energy is 1.8eV.We discuss the case from Asymptotic form and the sample.

The electroreflectance (ER) of surface-intrinsic-n+ type doped GaAs has exhibited many Franz-Keldysh oscillations to enable the application of fast Fourier transform to separate the heavy and light-hole transitions. In this work, we can get the dependence of surface electric field on external biased voltage from analyzing the Franz- Keldysh oscillations and the way of fast Fourier transform on condition that weakly modulated field, further more we can get the dependence of effective reduced mass on changed photon energy.

Any object can emit infrared radiation if their temperature higher than 0K.Because of this,the photodetectors for infrared radition is very important in application. First,this paper will introduce the kinds and properties of infrared photodetectors but most important is the quantum dot infrared photodetectors.In second chapter,we use the basic physic concepts and mathematical equations to infer the photocurrent and dark current formula. According to the formula,we can see the relationship between current and quantum dot density,bias,donorconcentration, Temperature. After we get the relationship,we can discuss the detectivity,noise properties, optical gain responstivity, differential photoconductivity. According to our research,the electron will be heated at very high ,bias and make the photoconductivity fairly smooth.Moreover,an increase in the effective temperature can result in the occurrence of the voltage range,where differential photoconductivity, is negative. It is important for a infrared photodetector to have high responsivity,detectivity,high working temperature,low dark current and low noise.Excepting this,to comprise a best infrared photodetector must have a good control on growth condition. Because of this,this paper will discuss the relationship between quantum dot and temperature,GRI time, growth thickness,deposited QD material.Finally,this paper find the best growth condition to form a quantum dot infrared photodetector.