[pt] A integração monolítica de um modulador com um guia de onda é de muito interesse para aplicação em comunicações ópticas pelo fato de que podemos diminuir as perdas por acoplamento óptico entre os dois dispositivos e usar moduladores curtos que operem em altas taxas de transmissão de dados. O crescimento epitaxial seletivo é uma das técnicas mais promissoras na atualidade para aplicação na integração monolítica de dispositivos semicondutores. Esta técnica permite controlar a espessura e a tensão das camadas crescidas seletivamente permitindo otimizar a integração e as características das estruturas dos dispositivos. A tese trata da implementação, do estudo e da aplicação do crescimento epitaxial seletivo por MOCVD de estruturas casadas e tensionadas de poços quânticos múltiplos de InGaAs/InAlAs para a fabricação de moduladores de amplitude baseados no efeito Stark e sua integração com guias de onda. O desempenho dos moduladores, baseados em estruturas de poços quânticos múltiplos de InGaAs/InAlAs que operam em 1,55 ym, é notavelmente melhorado quando é introduzida uma composição de 52% de Ga na liga e se tem um poço de ~100 A de espessura. Nesse caso, os moduladores possuem uma elevada figura de mérito e podem ser insensíveis à polarização. Nesse estudo foram crescidas várias amostras onde foi analisado o aumento na taxa de crescimento e a variação na composição das ligas de InGaAs e InAlAs em material bulk e em poços quânticos de InGaAs/InAlAs em função da geometria da máscara utilizada, i.e. diferentes larguras do dielétrico e largura da janela onde ocorre o crescimento fixo. Finalmente foram processados guias de onda cujas estruturas foram crescidas com a técnica de crescimento seletivo. Esses guias foram caracterizados por técnicas de campo próximo. / [en] The monolithic integration of a modulator with a waveguide is a lot of interest for application in optical communications for the fact in that can decrease the losses for optical joining between the two devices and to use short modulators that operate in high rates of transmission data. The selective growth is at the present time, one the more promising technique for application in the monolithic integration of semiconductors device. This technique allows to control the thickness and the stress of the grown layers allowing to improve the integration and the characteristics of the devices structures. These thesis is about the implementation, study and application of the selectuve growth by MOCVD of both match and tensile structures of multi quantum wells of inGaAs/InAlAs for the production of the amplitude modulators based on the Stark effect and its integration with waveguide. The performance of the modulators based on structures of multi quantum wells of InGaAs/InAlAs operating in 1,55 um, is notably improved whena Ga composition of 52% is used and the thickness of a quantum well is near to ~100 A. In that case, the modulators have a high figured of merit and they can be insensitive to the polarization. In this study, several samples was grown and the growing rate increase was analyzed and the variation of the composition in InGaAs and InAlAs in bulk alloys and in quantum wells of InGaAs/InAlAs in function of the window where the growth is spent. Finally, waveguides were processed whose structures were grown with the technique of selective growth. Those guides were characterized by the near field technique.

Superior properties of Silicon Carbide (SiC), such as wide bandgap, high breakdown field and high thermal conductivity, have made it the frontrunner to replace Silicon for applications requiring high breakdown strength, mechanical and radiation hardness. Commercial SiC devices are already available, although their expected performance has not yet been realized due to a few problems related to device fabrication technologies, such as selective doping. This work explores non-traditional techniques for SiC doping (and selective doping in particular) based on previously unknown types of defect reactions in SiC and novel epitaxial growth techniques, which offer advantages over currently available technologies. Recent developments in SiC epitaxial growth techniques at MSU have enabled the growth of high quality SiC epitaxial layers at record low temperatures of 1,300°C. Lower growth temperatures have enabled highly doped epilayers for device applications. Prototypes of SiC PiN diodes fabricated, demonstrated low values of the series resistance associated with anodes grown by the low temperature epitaxial growth technique. At room temperature, 100 ìm-diameter diodes with a forward voltage of 3.75 V and 3.23V at 1,000 A/cm2 before and after annealing were achieved. The reverse breakdown voltage was more than 680 V on average, even without surface passivation or edge termination. Reduced growth temperatures also enabled the possibility of selective epitaxial growth (SEG) of SiC with traditional masks used in the SEG in Si technology. Previously, SEG of SiC was impossible without high temperature masks. Good quality, defect free, selectively grown 4H-SiC epilayers were obtained using SiO2 mask. Nitrogen doped selectively grown epilayers were also obtained, which were almost completely ohmic, indicating doping exceeding 1x1019 cm-3. Moreover, conductivity modulation via defect reactions in SiC has been reported as a part of this work for the first time. The approach is based on a new phenomenon in SiC, named Recombination Induced Passivation (RIP), which was observed when hydrogenated SiC epilayers were subjected to above bandgap optical excitation. Additional acceptor passivation, and thereby modification of the conductivity of the epilayer, was observed. Results of investigations of the RIP process are presented, and conductivity modulation techniques based on the RIP process are proposed.

Neste trabalho, estudamos o crescimento de camadas semicondutoras de compostos III-V pela técnica de epitaxia por feixe molecular (MBE). Um grande esforço foi inicialmente realizado para entender o funcionamento do sistema inteiro e otimizar o uso de cada instrumento disponível para a caracterização in situ. Demos uma ênfase particular ao estudo da dopagem homogênea de camadas do tipo p usando duas novas técnicas e, pela primeira vez, obtivemos com sucesso camadas do tipo p crescidas pela co-evaporação de átomos de Si sobre susbtratos de GaAs (001). Finalmente, camadas de alta mobilidade eletrônica foram conseguidas, assim como espelhos de Bragg (DBRs) de alta refletividade. Estes dois tipos de estrutura possuem numerosas aplicações na indústria de microeletrônica e optoeletrônica / In this work, we studied the growth o f III-V semiconductor compounds by molecular beam cpitaxy (MBE). Much efTort was initially spem to understand the functioning of the whole system and optimize the use o f some specific instruments available for m si tu characterization. We gave some emphasis to the homogeneous doping o f p-type layers using two new techniques and, for the fírst time, a thick p-type GaAs layer was successfully grown using co-evaporation o f Si atoms on top o f (00 I) GaAs substrates. Finally, layers with high electron mobility were obtained, as well as distributed Bragg reflectors (DBRs) showing high retlectivity. These two types of structures have many applications in microelectronics and optoelectronics industry.

Neste trabalho, estudamos o crescimento de camadas semicondutoras de compostos III-V pela técnica de epitaxia por feixe molecular (MBE). Um grande esforço foi inicialmente realizado para entender o funcionamento do sistema inteiro e otimizar o uso de cada instrumento disponível para a caracterização in situ. Demos uma ênfase particular ao estudo da dopagem homogênea de camadas do tipo p usando duas novas técnicas e, pela primeira vez, obtivemos com sucesso camadas do tipo p crescidas pela co-evaporação de átomos de Si sobre susbtratos de GaAs (001). Finalmente, camadas de alta mobilidade eletrônica foram conseguidas, assim como espelhos de Bragg (DBRs) de alta refletividade. Estes dois tipos de estrutura possuem numerosas aplicações na indústria de microeletrônica e optoeletrônica / In this work, we studied the growth o f III-V semiconductor compounds by molecular beam cpitaxy (MBE). Much efTort was initially spem to understand the functioning of the whole system and optimize the use o f some specific instruments available for m si tu characterization. We gave some emphasis to the homogeneous doping o f p-type layers using two new techniques and, for the fírst time, a thick p-type GaAs layer was successfully grown using co-evaporation o f Si atoms on top o f (00 I) GaAs substrates. Finally, layers with high electron mobility were obtained, as well as distributed Bragg reflectors (DBRs) showing high retlectivity. These two types of structures have many applications in microelectronics and optoelectronics industry.

Vertical cavity surface emitting lasers (VCSELs) are today a commodity on the short wavelength laser market due to the ease with which they are manufactured. Much effort has in the last decade been directed towards making long wavelength VCSELs as successful in the marketplace. This has not been achieved due to the much more difficult fabrication technologies needed for realising high performance long wavelength VCSELs. At one point, GaInNAs quantum wells gain regions grown on GaAs substrates seemed to be the solution as it enabled all-epitaxial VCSELs that could make use of high contrast AlGaAs-based distributed Bragg reflectors (DBRs) as mirrors and lateral selective oxidation for optical and electrical confinement, thereby mimicking the successful design of short wavelength VCSELs. Although very good device results were achieved, reproducible and reliable epitaxial growth of GaInNAs quantum wells proved difficult and the technology has not made its way into high-volume production. Other approaches to the manufacturing and material problems have been to combine mature InP-based gain regions with high contrast AlGaAs-based DBRs by wafer fusion or with high contrast dielectric DBRs. Commonly, a patterned tunnel junction provides the electrical confinement in these VCSELs. Excellent performance has been achieved in this way but the fabrication process is difficult. In this work, we have employed high strain InGaAs quantum wells along with large detuning between the gain peak and the emission wavelength to realize GaAs-based long wavelength VCSELs. All-epitaxial VCSELs with AlGaAs-based DBRs and lateral oxidation confinement were fabricated and evaluated. The efficiency of these VCSELs was limited due to the optical absorption in the doped DBRs. To improve the efficiency and manufacturability, two novel optical and electrical confinement schemes based on epitaxial regrowth of current blocking layers were developed. The first scheme is based on a single regrowth step and requires very precise processing. This scheme was therefore not developed beyond the first generation but single mode power of 0.3 mW at low temperature, -10ºC, was achieved. The second scheme is based on two epitaxial regrowth steps and does not require as precise processing. Several generations of this design were manufactured and resulted in record high power of 8 mW at low temperature, 5ºC, and more than 3 mW at high temperature, 85ºC. Single mode power was more modest with 1.5 mW at low temperature and 0.8 mW at high temperature, comparable to the performance of the single mode lateral oxidation confined VCSELs. The reason for the modest single mode power was found to be a non-optimal cavity shape after the second regrowth that leads to poor lateral overlap between the gain in the quantum wells and the intensity of the optical field. / QC 20100825

No description available.

The objective of this research was to perform a systematic investigation of the unique structural and electrical properties of epitaxial graphene at the nanoscale. As the semiconductor industry faces increasing challenges in the production of integrated circuits, due to process complexity and scaling limitations, new materials research has come to the forefront of both science and engineering disciplines. Graphene, an atomically-thin sheet of carbon, was examined as a material which may replace or become integrated with silicon nanoelectronics. Specifically, this research was focused on epitaxial graphene produced on silicon carbide. This material system, as opposed to other types of graphene, holds great promise for large-scale manufacturing, and is therefore of wide interest to the academic and industrial community. In this work, high-quality epitaxial graphene production was optimized, followed by the process development necessary to fabricate epitaxial graphene nanoribbon transistors for electrical characterization. The structural and electrical transport properties of the nanoribbons were elucidated through a series of distinct experiments. First, the size-dependent conductivity of epitaxial graphene at the nanoscale was investigated. Next, the alleviation of the detrimental effects revealed during the size-dependent conductivity study was achieved through the selective functionalization of graphene with hydrogen. Finally, two techniques were developed to allow for the complementary doping of epitaxial graphene. All of the experiments presented herein reveal new and important aspects of epitaxial graphene at the nanoscale that must be considered if the material is to be adopted for use by the semiconductor industry.

The present study aims at clarifying the effects of processing parameters and substrate orientation on the epitaxial growth of Ni on polycrystalline Cu by electrodeposition from a sulfamate solution. The deposits were analyzed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), auger electron spectroscopy (AES) and transmission electron microscopy (TEM). Two morphologies: rough and smooth, of the substrate surface were introduced by electropolishing. Auger electron spectroscopy showed that Ni was deposited on both areas without preference. However, the deposition rate for the rough area was slightly higher at a low current density of 0.01 A/dm2. At higher current densities, both areas possessed the same rate of deposition. In-plane TEM results demonstrated that Ni deposited on Cu epitaxially regardless the orientation of the Cu grains, electrolyte temperature and current density. EBSD analysis indicated that the Ni epilayer with an orientation of <001>//ND grew epitaxially to as thick as 12 £gm, whereas randomly oriented Ni nucleated on the epilayer having orientations of <011>//ND or <-111>//ND on prolonging deposition at current of 10 A/dm2. In other words, the epitaxial growth of Ni on Cu cannot be sustained to a thickness of hundreds of micrometers without a <001>//ND orientation.

In the past several years, epitaxial graphene on silicon carbide has been transformed from an academic curiosity of social scientists to a leading candidate material to replace silicon in post-CMOS electronics. This has come with rapid development of growth technologies, improved understanding of epitaxial graphene on the polar faces of silicon carbide, and new device fabrication techniques. The contributions of this thesis include refinement and improved understanding of graphene growth on the silicon- and carbon-faces in the context of managed local silicon partial pressure, high-throughput epitaxial graphene thickness measurement and uniformity characterization by ellipsometry, observations of nearly ideal graphene band structures on rotationally stacked carbon-face multilayer epitaxial graphene, presentation of initial experiments on localized in situ chemical modification of epitaxial graphene for an alternate path to semiconducting behavior, and novel device fabrication methods to exploit the crystal structure of the silicon carbide substrate. The latter is a particularly exciting foray into three dimensional patterning of the substrate that may eliminate the critical problem of edge roughness in graphene nanoribbons.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14050号 / 工博第2962号 / 新制||工||1439(附属図書館) / 26329 / UT51-2008-F442 / 京都大学大学院工学研究科電子物性工学専攻 / (主査)教授 鈴木 実, 教授 髙岡 義寛, 教授 藤田 静雄 / 学位規則第4条第1項該当