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The epitaxial growth of GaN and A1GaN/GaN Heterostructure Field Effect Transistors (HFET) on Lithium Gallate (LiGaO₂) substratesKang, Sangbeom 12 1900 (has links)
No description available.
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Deep-Ultraviolet Optoelectronics Based on GaN Quantum Disks and Bio-Inspired NanostructuresSubedi, Ram Chandra 11 1900 (has links)
Optoelectronics in the deep-ultraviolet (DUV) regime is still a growing research field that requires significant effort to understand the material properties and optimize the device structures to realize efficient DUV devices. Aluminum gallium nitride (AlGaN) is perhaps the most studied semiconductor to replace the environmentally hazardous mercury lamps; however, the external quantum efficiency of AlGaN based DUV devices is insufficient to replace the existing old-fashioned mercury UV lamps. Despite the tunability in the bandgap of AlGaN, the excessive strain accumulation associated with increased alloying of Al in AlGaN and the poor dopant activation due to the relatively large ionization energy of the donors and acceptors are not favorable for realizing efficient DUV emitters. In addition, the crossover among the light hole, heavy hole and split-off bands in the valance band for Al-rich AlGaN suppresses the transverse-electric polarization, which further worsens the external quantum efficiency. Furthermore, for DUV photodetection, commercially available Si-photodetectors suffer from poor responsivity for wavelengths shorter than 400 nm in contrast to the visible spectrum. Hence, the-state-of-art photodetectors in the DUV regime also need a significant upgrade, particularly for high-speed applications.
Firstly, we utilized the high quantum confinement in plasma-assisted MBE grown ultrathin GaN QDisks to realize DUV (λ ≈ 260 nm) emission using a binary compound (GaN) in contrast to conventionally used ternary compound (AlGaN). More importantly, we experimentally demonstrated TE-dominant DUV emission, unlike Al-rich AlGaN, illustrating a unique pathway for realizing efficient DUV vertical emitters. Secondly, inspired by the light manipulation technique practiced in nature, we presented iridocytes on giant clams (Tridacna maxima), known for their symbiotic relationship with algae as a color downconverting material for DUV photodetection. Investigating the structural and optical properties of iridocytes found in Tridacna maxima, we established a robust UV communication allowing the data transfer rate of 100 Mbit/s within the forward error correction limit for modulated 375 nm-laser diode. Using a similar matrix implemented to 375 nm-laser, with high-power UV-C LED (λ ≈ 278 nm), we could establish an optical wireless communication that could allow a data-transmission rate of tens of Mbit/s within the forward error correction limit.
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Study of HfN as seed layer for next generation of BAW RF filters : synthesis, characterization, and investigation of piezoelectric performanceLlorens Balada, Eduard January 2020 (has links)
Micro-electro-mechanical systems (MEMS) have become an essential component of a wide range ofelectronic devices over the last decades such as accelerometers, microphones, gas sensors, and filters.During this new millennium, a new radio frequency (RF) technology has been developed to satisfy thetough demands that arose due to the implementation of 5G wireless communication: bulk acoustic wave(BAW) filters.BAW devices use the piezoelectric effect, converting mechanical vibrations to electrical signals, topower wireless devices. BAW filters can operate between 3.5 GHz and 6 GHz, therefore, within therange of the new 5G. BAW technology offers lower insertion loss, higher heat dissipation, andperformances at higher power and frequency which increases the data speed considerably.This thesis will be focused on the study of the materials used in BAW devices. A common BAW filteris made from different layers distributed in a stack, from the bottom to the upper part, the BAW filteris composed of a substrate, a transducer layer made of a piezoelectric layer in between of two electrodes,and intermediate layers that can enhance the addition of the deposited layers on top called buffer layers,or the crystal quality of the films on top called seed layers.The main characteristic that a buffer layer must possess is an intermediate lattice parameter betweenthat of the substrate and the top layer. When these two layers present a high lattice mismatch, theinterface quality is rather poor. By using a buffer layer, and therefore, by adding two different interfaces,the crystal quality is improved by decreasing the internal stress and the crystal distortion. Buffer layermaterials depend on the type of materials that will be in contact with them.A seed layer is usually used to improve the crystal quality of a layer that requires extreme sputteringparameters to be used to be deposited possessing a high crystal quality and a preferred orientation. Seedlayers used in BAW devices, whose piezoelectric layer is made of AlScN or AlN, are usually made ofhighly c-axis oriented and highly crystalline AlN.The objective of this study is to analyze the deposition of AlN and HfN by means of reactive radiofrequency magnetron sputtering and reactive pulsed-direct current magnetron sputtering, respectively.AlN is largely used as a buffer layer and as a seed layer, however, the new approach of this report is tostudy the sputtering of HfN and compare it as a possible candidate to replace AlN as a seed layer.
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Electronic structures and optical properties of Sn(II) ternary oxides / 二価スズ複合酸化物の電子構造と電気・光学特性Katayama, Shota 23 March 2015 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18982号 / 工博第4024号 / 新制||工||1620(附属図書館) / 31933 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 酒井 明, 教授 邑瀬 邦明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
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Epitaxial Growth and Superconducting Properties of 1212 Copper Oxides / 1212型銅酸化物のエピタキシャル成長とその超伝導特性Komori, Sachio 23 March 2016 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19720号 / 工博第4175号 / 新制||工||1644(附属図書館) / 32756 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 川上 養一, 教授 田中 勝久, 准教授 掛谷 一弘 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
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Crystalline properties of gallium oxide thin films epitaxially grown by mist chemical vapor deposition / ミスト化学気相法によるエピタキシャル成長酸化ガリウム薄膜の結晶特性に関する研究Lee, Sam-Dong 23 March 2016 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19721号 / 工博第4176号 / 新制||工||1644(附属図書館) / 32757 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 藤田 静雄, 教授 髙岡 義寛, 准教授 須田 淳 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
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Vapor-Liquid-Solid Growth of Semiconductor SiC Nanowires for Electronics applicationsThirumalai, Rooban Venkatesh K G 17 August 2013 (has links)
While investigations of semiconductor nanowires (NWs) has a long history, a significant progress is yet to be made in silicon carbide (SiC) NW technologies before they are ready to be utilized in electronic applications. In this dissertation work, SiC NW polytype control, NW axis orientation with respect to the growth substrate and other issues of potential technological importance are investigated. A new method for growing SiC NWs by vapor-liquid-solid mechanism was developed. The method is based on an in-situ vapor phase delivery of a metal catalyst to the growth surface during chemical vapor deposition. This approach is an alternative to the existing seeded catalyst method based on ex-situ catalyst deposition on the target substrate. The new SiC NW growth method provided an improved control of the NW density. It was established that the NW density is influenced by the distance from the catalyst source to the substrate and is affected by both the gas flow rate and the catalyst diffusion in the gas phase. An important convenience of the new method is that it yields NW growth on the horizontal substrate surfaces as well as on titled and vertical sidewalls of 4H-SiC mesas. This feature facilitates investigation of the NW growth trends on SiC substrate surfaces having different crystallographic orientations simultaneously, which is very promising for future NW device applications. It was established that only certain orientations of the NW axes were allowed when growing on a SiC substrate. The allowed orientations of NWs of a particular polytype were determined by the crystallographic orientation of the substrate. This substrate-dependent (i.e., epitaxial) growth resulted in growth of 3C-SiC NWs in total six allowed crystallographic orientations with respect to the 4H-SiC substrate. This NW axis alignment offers an opportunity to achieve a limited number of NW axis directions depending on the surface orientation of the substrate. The ease of controlling the NW density enabled by the vapor-phase catalyst delivery approach developed in this work, combined with the newly obtained knowledge about how to grow unidirectional (wellaligned) NW arrays, offer new opportunities for developing novel SiC NW electronic and photonic devices.
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[pt] CRESCIMENTO EPITAXIAL SELETIVO DE ESTRUTURAS SEMICONDUTORAS III-V VISANDO A INTEGRAÇÃO OPTOELETRÔNICA / [en] SELECTIVE AREA EPITAXIAL GROWTH OF III-V SEMICONDUCTOR STRUCTURES FOR OPTOELECTRONIC APPLICATIONSFRANCISCO JUAN RACEDO NIEBLES 07 December 2005 (has links)
[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.
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Low Carbon n-GaN Drift Layers for Vertical Power Electronic DevicesCarlson, Eric Paul 14 July 2023 (has links)
GaN holds significant potential as a material for vertical p-n diodes, enabling the realization of devices with reverse breakdown voltages of 5 kV or higher. Carbon serves as the primary compensating dopant in the growth process, incorporated into GaN during metalorganic chemical vapor deposition (MOCVD) growth. The level of carbon incorporation depends on several factors, including growth rate, ammonia flow, temperature, pressure, and trimethylgallium (TMGa) flow. Through guided empirical modeling, it was demonstrated that the carbon incorporation in GaN growth could be predicted using a single parameter based on the ratio of ammonia flow to the growth rate. This model accurately predicts carbon concentrations ranging from 1x1017 to 5x1014 cm-3 while allowing for maximized growth rates. Other extrinsic dopants have either been reduced below the threshold of consideration or modeled using similar single-parameter relationships. By identifying the dominant extrinsic dopants and accounting for them, an intrinsic defect with a concentration of 2.2x1015 cm-3 was identified. By combining these relationships, growth conditions for n-GaN were optimized, resulting in electron concentrations as low as 1x1015 cm-3. Leveraging these techniques, p-n diodes were grown, achieving a reverse breakdown voltage as high as 3.1 kV. / Doctor of Philosophy / Power electronic devices based on vertical GaN have the potential to revolutionize applications such as electric vehicles, solar charging systems, and the smart grid. However, there are significant materials challenges that need to be addressed in order to realize these devices. They must be extremely pure and extremely thick. Unfortunately, the primary source of these materials also contains carbon, which can negatively impact purity. To overcome this challenge, an empirical model for the growth process has been developed. This model enables independent control over the carbon source and the removal of carbon, using a single parameter. By leveraging this model, it becomes possible to optimize the trade-off between high purity, high growth rates, and ideal electronic properties. Using these techniques, devices were grown with next-generation levels of performance at minimal time and cost.
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Effect of fluid dynamics and reactor design on the epitaxial growth of gallium nitride on silicon substrate by metalorganic chemical vapor depositionGao, Yungeng January 2000 (has links)
No description available.
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