Epitaxial Growth of Aligned AlGalnN Nanowires by Metal-organic Chemical Vapor Deposition PDF Download
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Languages : en
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Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. 1010 M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.
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Languages : en
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Book Description
Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. 1010 M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.
Author: Sema Ermez
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Languages : en
Pages : 143
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III-V semiconductor epitaxial nanowires have gained significant attention in recent years, as they showcase an opportunity to combine III-V material properties with a non-planar morphology. To date, semiconductor devices have been continuously engineered to realize optoelectronic devices with ever smaller size, higher efficiency, and lower power consumption. However, many device improvements have reached fundamental physical limitations. One way to address these challenges is to adapt a non-planar device structure. Nanowires are onedimensional structures that can be grown on a substrate with epitaxial relationship using traditional vapor deposition techniques such as metal-organic chemical vapor deposition (MOCVD). Therefore, the novelty of non-planar morphology can be achieved using industrial scale high throughput deposition techniques. To realize the full potential of nanowires as building blocks in a range of different devices, growth of nanowire arrays with controlled density, morphology, composition and alignment is necessary. In this thesis, we demonstrate controlled growth of self-seeded III-V binary and ternary nanowires by MOCVD. First, self-seeded binary III-V nanowire growth is demonstrated for gallium (Ga)-seeded gallium arsenide (GaAs) nanowires. High yield of vertical nanowires are grown reproducibly by a two-step approach: in situ deposition of Ga seed particles at high temperatures (500°C - 600°C), followed by GaAs nanowire growth at lower temperatures (420°C - 435°C). The fabricated GaAs nanowires show a single crystalline structure at the base and occasional twin planes along the nanowire growth direction. We develop a growth model based on incorporation and extraction of Ga from seed particle to explain the observed tapering of nanowires. Second, control over the density and diameter of nanowire arrays is achieved by controlling seed deposition conditions. We demonstrate that higher seed deposition temperatures or changing the GaAs substrate orientation from (11 )A to (110) and (11 1)B yield reduced areal density and larger nanowire diameters. Seed deposition temperature affects the surface diffusion of Ga adatoms, whereas substrate orientation affects the nucleation of seed particles due to varied chemical potential of Ga adatoms and surface energies on different surface orientations. Lastly, controlled self-seeded ternary III-V nanowire growth is realized in the case of Ga-seeded GaAs1-xPx nanowire growth on GaAs substrates. Composition control for x = 0 - 0.3 and growth of GaP nanowires are demonstrated by varying group-V precursor percentage. It was found that strain due to lattice mismatch between GaAs substrate and GaAsP nanowires can be released due to nanowire geometry. Cathodoluminescence measurements have shown emission of light in GaAsP band gap energies, confirming the successful growth of nanowires in this ternary material system. The methods developed for self-seeded growth of GaAs and GaAsP nanowires, as well as density and diameter control of self-seeded growth are extendable to other self-seeded III-V nanowire material systems.
Author: Toshio Kanno
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Languages : ja
Pages : 18
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Author: Nan Zheng
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Category : Energy conversion
Languages : en
Pages : 292
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The goal of this dissertation is to advance photovoltaics via two possible approaches: (1) technologies that have the potential to increase energy conversion efficiency; and (2) substitutes for single-crystal wafers to lower the areal production costs. Short-period superlattices are proposed candidates for next-generation photovoltaics with higher theoretical efficiency. In this work, we report the metalorganic chemical vapor deposition (MOCVD) and characterization of epitaxial nanowires self-assembled in GaAs/GaAsP short-period superlattices grown on lattice-mismatched GaAsP compositional grade on 6°-111B miscut GaAs substrates. The nanowires extend along 110A and have a lateral spacing of ~70-90 nm and a height of ~4 nm. In addition to the anisotropy observed in 110A and 110B, transmission electron microscopy (TEM) plan-view and atomic force microscopy examinations confirmed the nanowire morphology observed in TEM cross-section. These nanowires may simultaneously enable both electronic miniband formation and lateral charge transport.
Author: Seth A. Fortuna
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Languages : en
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The semiconductor nanowire has been widely studied over the past decade and identified as a promising nanotechnology building block with application in photonics and electronics. The flexible bottom-up approach to nanowire growth allows for straightforward fabrication of complex 1D nanostructures with interesting optical, electrical, and mechanical properties. III-V nanowires in particular are useful because of their direct bandgap, high carrier mobility, and ability to form heterojunctions and have been used to make devices such as light-emitting diodes, lasers, and field-effect transistors. However, crystal defects are widely reported for III-V nanowires when grown in the common out-of-plane 111B direction. Furthermore, commercialization of nanowires has been limited by the difficulty of assembling nanowires with predetermined position and alignment on a wafer-scale. In this thesis, planar III-V nanowires are introduced as a low-defect and integratable nanotechnology building block grown with metalorganic chemical vapor deposition. Planar GaAs nanowires grown with gold seed particles self-align along the 110 direction on the (001) GaAs substrate. Transmission electron microscopy reveals that planar GaAs nanowires are nearly free of crystal defects and grow laterally and epitaxially on the substrate surface. The nanowire morphology is shown to be primarily controlled through growth temperature and an ideal growth window of 470 +- 10 °C is identified for planar GaAs nanowires. Extension of the planar growth mode to other materials is demonstrated through growth of planar InAs nanowires. Using a sacrificial layer, the transfer of planar GaAs nanowires onto silicon substrates with control over the alignment and position is presented. A metal-semiconductor field-effect transistor fabricated with a planar GaAs nanowire shows bulk-like low-field electron transport characteristics with high mobility. The aligned planar geometry and excellent material quality of planar III-V nanowires may lead to highly integrated III-V nanophotonics and nanoelectronics.
Author: Kamran Matthew Varahramyan
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Category :
Languages : en
Pages :
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Author: Jyh-Chia Chen
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Category : Compound semiconductors
Languages : en
Pages : 165
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Author: Timothy David Veal
Publisher: CRC Press
ISBN: 1439859612
Category : Technology & Engineering
Languages : en
Pages : 707
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Written by recognized leaders in this dynamic and rapidly expanding field, Indium Nitride and Related Alloys provides a clear and comprehensive summary of the present state of knowledge in indium nitride (InN) research. It elucidates and clarifies the often confusing and contradictory scientific literature to provide valuable and rigorous insight into the structural, optical, and electronic properties of this quickly emerging semiconductor material and its related alloys. Drawing from both theoretical and experimental perspectives, it provides a thorough review of all data since 2001 when the band gap of InN was identified as 0.7 eV. The superior transport and optical properties of InN and its alloys offer tremendous potential for a wide range of device applications, including high-efficiency solar cells and chemical sensors. Indeed, the now established narrow band gap nature of InN means that the InGaN alloys cover the entire solar spectrum and InAlN alloys span from the infrared to the ultraviolet. However, with unsolved problems including high free electron density, difficulty in characterizing p-type doping, and the lack of a lattice-matched substrate, indium nitride remains perhaps the least understood III-V semiconductor. Covering the epitaxial growth, experimental characterization, theoretical understanding, and device potential of this semiconductor and its alloys, this book is essential reading for both established researchers and those new to the field.
Author: Francis Gudyanga
Publisher: CRC Press
ISBN: 1000730239
Category : Technology & Engineering
Languages : en
Pages : 306
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Book Description
Africa’s dire need to industrialize is universally acknowledged and it is evident that the continent’s vast mineral resources can catalyze that industrialization. This requires the promotion of local beneficiation and value addition of minerals to yield materials on which modern Africa’s industry and society can rely. This book is, therefore, about transforming Africa’s comparative advantages in minerals into the continent’s competitive edge regarding materials. Mineral beneficiation and value addition form the basis and provide opportunities for mineral-driven Africa’s industrialization. The scope of the book is three-fold with inter-connected relationships: Information, Technical, and Policy oriented. It will be a useful reference material for mining undergraduate students on beneficiation and value addition of each of the minerals found in Africa. The book, while presenting a broad overview of beneficiation and value addition of Africa’s minerals, provides crucial starting material for postgraduate research students and R&D institutions who wish to delve into more advanced methods of extraction and utilization of mineral-derived materials that are in Africa for the purpose of industrialization of the continent.
