The Effects of Rare Earth Doping on Gallium Nitride Thin Films PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download The Effects of Rare Earth Doping on Gallium Nitride Thin Films PDF full book. Access full book title The Effects of Rare Earth Doping on Gallium Nitride Thin Films by Stephen R. McHale. Download full books in PDF and EPUB format.
Author: Stephen R. McHale
Publisher:
ISBN:
Category : Rare earths
Languages : en
Pages : 318
Get Book Here
Book Description
Author: Stephen R. McHale
Publisher:
ISBN:
Category : Rare earths
Languages : en
Pages : 318
Get Book Here
Book Description
Author: Wang Rui
Publisher:
ISBN:
Category :
Languages : en
Pages : 130
Get Book Here
Book Description
Rare Earth (RE) doped III-nitrides are being widely investigated for potential applications in optical communication and displays, due to the wide and direct energy bandgap of GaN resulting in low thermal quenching of RE ion sharp emission from ultraviolet (UV) through visible to infrared (IR) region. The UC Nanolab has been conducting RE doped GaN research for more than 10 years and many achievements were obtained, ranging from material growth to device fabrication. This dissertation studied RE emission in GaN material, focusing on the effects of electronic impurity (Si) co-doping on RE luminescence. Advanced RE doped GaN electroluminescent devices (ELDs) were also designed and fabricated. Detailed device characterization was carried out and the effect of co-dopant was investigated. Eu-doped GaN thin films were grown on sapphire wafers by molecular beam epitaxy (MBE) technique and the growth conditions were optimized for the strongest Eu luminescence. It was found that GaN thin film quality and Eu doping concentration mutually affected Eu luminescence. High quality GaN:Eu thin films were grown under Ga rich condition (III/V>1), but the strongest Eu luminescence was obtained under slightly N rich condition (III/V1). The optimum Eu doping concentration is ~0.1-1.0at.%, depending on the GaN:Eu thin film quality. Higher growth temperature (750°C) was also found to enhance Eu luminescence intensity (~10x) and efficiency (~30x). The effect of Si co-doping in GaN:RE thin films was investigated. Eu photoluminescence (PL) was enhanced ~5-10x by moderate Si co-doping (~0.05at.%) mostly due to the increase of Eu PL lifetime, but decreased very fast at high Si co-doping concentration (>0.08at.%). The increase of Eu PL lifetime is possibly due to the incorporation of Si uniformly distributing Eu ions and shielding Eu-Eu interactions. Combined with the increase in excitation cross section and carrier flux, there is a significant enhancement on Eu PL intensity. The electrical properties of GaN:RE thin films were changed from high resistive to weakly n-type due to increased electron concentration introduced by Si co-doping. GaN:RE ELDs were fabricated and the electrical and optical properties were studied by I-V and electroluminescence (EL) measurements. A hetero-junction PIN structure was designed on n-GaN:Si/GaN:RE/p-Si, employing p-Si substrates as p-type conductive layer. RE ions EL emission was found to be much stronger under forward bias than under reverse bias. The Si co-doping was also studied in GaN:RE ELDs. It was found that Er EL had strong visible & IR emission under forward bias, while there is little or no emission under reverse bias. A pn hetero-junction structure formed between p-Si and n-GaN:(Si, Er) layers was proposed to be responsible for the emission control. GaN:(Si, Eu) AC thin film ELDs were also fabricated and shown that the Si co-doping increased the Eu ions emission intensity and efficiency.
Author: Jonathan Huai-Tse Tao
Publisher:
ISBN: 9781124339528
Category :
Languages : en
Pages : 165
Get Book Here
Book Description
A three-step solution-based process had been used synthesize powders of GaN, AlN and their alloys. The complete solid solubility and tunable nature of these nitride band gaps in the visible spectrum were the motivation of these studies due to their application in solid state lighting. Energy dispersive X-ray spectroscopy confirmed the reduction in oxygen content for the GaN powders to as low as 4 atom % with an 8 % oxygen to nitrogen ratio. Relative to commercial GaN powders, the bandedge of the powders synthesized by such approach also shifted to higher energy, which indicated fewer defects, as observed from reflectance measurements. Inspired by the use of rare-earth elements as color emitters in fluorescent lamp phosphors, these elements were also used as activators in our nitride material. Visible emission was demonstrated through photoluminescence measurements in AlN powders activated with rare-earth elements Eu3, Tb3, Tm3+. These ions showed emission in the red, green and blue regions of the visible spectrum, respectively. Eu3+ and Tb3+ co-activation was also observed in an AlN sample that indicated successful energy transfer from the host to sensitizer, and subsequently to another activator. Tb3+ emission was observed under cathodoluminescence in GaN powders synthesized by the same method, and a concentration study showed no effect of concentration quenching up to 8 atom %. Using the same source powder, a pulsed-laser deposited thin film was fabricated that showed both band gap emission and activator-related emission, suggesting a reduction of defects when the powders were deposited as thin films. Additionally, GaN:Tb3+ films were also fabricated using metallorganic vapor phase epitaxy using precursors with and without oxygen ligands. Tb3+ emission was only observed in the sample fabricated from the precursor with oxygen ligand, suggestion that oxygen may be required for effective rare earth luminescence. Finally, Ga1-xAl/xN alloy powders (x = 0.5) and Ga1-x-yAl/xDy/yN (x = 0.10, 0.30, y = 0.01) powders were synthesized using the solution method while incorporating a stainless steel pressure vessel, which increased the synthesis pressure and aided the formation of a single phase hydroxide precursor. This in turn produced a single phase alloy nitride in the final step. Dy3+ emission that was not observed in GaN powders was also observed in the Ga1-x-yAl/xDy/yN powder. This suggested that the incorporation of aluminum enabled rare-earth emission in the nitrides synthesized for these experiments. However, attempts to sputter nitride alloy thin films via radio frequency sputtering were unsuccessful; only very minor peak shifts in the X-ray diffraction patterns were observed. Nevertheless, energy dispersive X-ray spectroscopy indicates the presence of Al in the Ga0.5Al0.5N film deposited on a Si substrate. This suggested that Al atoms may have segregated from the alloy lattice during the deposition process, with only a small amount of Al atoms incorporated into the GaN lattice.
Author: V. Dierolf
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 318
Get Book Here
Book Description
This book brings together more than 100 specialists from around the world to examine the status and emerging trends in the field of rare-earth-doped materials. These materials are used and/or are potential candidates for applications as lasers, light-emitting diodes, phosphors, displays and other photonic applications. Progress in growth, doping methods, characterization and device applications are reviewed. Topics include: rare-earth doping in nitrides; rare-earth doping in silicon-related materials; mechanisms and laser materials and phosphors and scintillators.
Author: Alaa Eldin Giba
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Author: Xingmin Cai
Publisher: Open Dissertation Press
ISBN: 9781361238172
Category :
Languages : en
Pages :
Get Book Here
Book Description
This dissertation, "Growth, Doping and Nanostructures of Gallium Nitride" by Xingmin, Cai, 蔡興民, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled GROWTH, DOPING AND NANOSTRUCTURES OF GALLIUM NITRIDE Submitted by Cai Xing Min for the degree of Doctor of Philosophy at The University of Hong Kong in September 2005 Due to its exceptional properties, such as the direct and wide band gap and high thermal stability, gallium nitride (GaN) is widely used in optoelectronics and high temperature/high power devices. Moreover, GaN has great potential for spintronic and nanoelectronic applications. Hence research on the nanostructures and doping of GaN has become intensive in recent years. Theoretical calculations predict that Mn doped GaN has Curie temperatures above room temperature. However, experimental results have not been consistent and a wide range of magnetic properties was reported for GaN: Mn. In this work, doping by thermal diffusion and doping during molecular beam epitaxy (MBE) growth were investigated. It was found that GaN wafers doped with Mn and Cr by thermal diffusion were ferromagnetic at 300 K, while for the MBE grown GaMnN samples, ferromagnetism up to 56 K was observed. This illustrates the importance of the material quality and the doping mechanism on the magnetic properties of the sample. One possible way to achieve improved material quality of GaN is to fabricate nanowires instead of thin films. Due to the lack of lattice matched substrates for GaN, it is difficult to grow epitaxial layers with low concentration of defects. On the other hand, GaN nanowires with good crystalline quality could be grown on a wider range of substrates. Therefore, systematic investigation of GaN nanowire growth has been performed. The effects of catalyst, temperature, and Ga to N ratio on the obtained morphology of GaN were studied. It was found that metallic Ni and Au were suitable catalysts for GaN nanowire growth, while nickel nitrate resulted in the growth of SiO nanowire bunches. The effect of the Ga/N ratio on the morphology of GaN nanowires was studied in detail for Ni catalyzed growth. It was found that the morphology of GaN nanowires strongly depended on the Ga/N ratio. In relatively Ga rich condition, smooth-surfaced GaN nanowires grew along [1010], while in relatively N rich condition, a mixture of smooth-surfaced and stacked-cone GaN nanowires growing along [0001] was obtained. In addition, in the N rich condition, lateral growth of GaN nanowires and a completely new morphology were observed. The growth mechanisms responsible for the different morphologies were discussed. In addition, growth of InN and In Ga N nanostructures was also studied. x 1-x Different catalysts were tested for growing InN nanowires, and successful fabrication of nanowires was achieved for Au and Ag. Both hexagonal and cubic InN nanorods with polyhedral ends were obtained and their formation mechanism was discussed. In Ga N nanowires with a core/shell structure were successfully fabricated. Free x 1-x standing In Ga N nanocoils and In Ga N nanowires coiled around one another x 1-x x 1-x were observed with longer growth time and on substrates with thicker gold layers. DOI: 10.5353/th_b3580639 Subjects: Semiconductor doping Nanostructures Gallium nitride
Author: Volkmar Dierolf
Publisher: Woodhead Publishing
ISBN: 008100060X
Category : Science
Languages : en
Pages : 472
Get Book Here
Book Description
Rare Earth and Transition Metal Doping of Semiconductor Material explores traditional semiconductor devices that are based on control of the electron’s electric charge. This book looks at the semiconductor materials used for spintronics applications, in particular focusing on wide band-gap semiconductors doped with transition metals and rare earths. These materials are of particular commercial interest because their spin can be controlled at room temperature, a clear opposition to the most previous research on Gallium Arsenide, which allowed for control of spins at supercold temperatures. Part One of the book explains the theory of magnetism in semiconductors, while Part Two covers the growth of semiconductors for spintronics. Finally, Part Three looks at the characterization and properties of semiconductors for spintronics, with Part Four exploring the devices and the future direction of spintronics. Examines materials which are of commercial interest for producing smaller, faster, and more power-efficient computers and other devices Analyzes the theory behind magnetism in semiconductors and the growth of semiconductors for spintronics Details the properties of semiconductors for spintronics
Author: Junxia Shi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
As an essential component for all power electronic systems, power semiconductor devices have a major impact on the economy, determining the cost and efficiency of the power electronic systems. As Si based devices have approached their theoretical material limits, wide bandgap materials such as GaN and SiC are attracting a lot of interests for drastic performance improvements to meet the severe operation requirements in the future. In addition, optical applications based on group-III nitrides have attracted tremendous interests in recent years, along with the material growth advancements. This dissertation focuses on high voltage GaN-based field effect transistors for high voltage, low loss power switching applications, as well as rare earth doping in GaN particles for optical applications. AlGaN/GaN heterostructure field effect transistors were designed, fabricated, and characterized to systematically study the effects of the key design parameters on current density and off-state breakdown voltage. However, the breakdown criterion of 1 mA/mm is impractical for real applications, because of the unacceptably high power consumption at the off state. Moreover, the lack of an appropriate surface passivation has long been a bottleneck for the GaN high voltage switching research community. To solve these problems, AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors were designed, fabricated and characterized, with HfO2 as the gate insulator and surface passivation. These devices exhibited breakdown voltages of 1035 V for a gate-drain spacing of 10 [MICRO SIGN]m, specific on-resistances of 0.9 m[OMEGA]-cm2, ultra-low gate and drain leakage currents, and minimized current slump under pulse measurements. This is the best performance ever reported on GaN-based powerswitching devices, which efficiently combines device forward, reverse, and switching characteristics. The performance of GaN devices is evidenced for the first time to go beyond the theoretical material limit of SiC. Eu doping in GaN for optical applications was also investigated in this dissertation. The effect of growth temperature on crystallinity, Eu incorporation and luminescence was investigated, and the Eu doping concentration was extracted nondestructively by strain analysis of the correlated Raman and X-ray Diffraction data. Furthermore, electrophoretic deposition was developed to fabricate thin films out of the nanoparticles.
Author: Nathaniel T. Woodward
Publisher:
ISBN: 9781124657868
Category :
Languages : en
Pages : 186
Get Book Here
Book Description
Understanding the excitation mechanisms of rare earth ions in materials used for optoelectronic applications is key to achieving more efficient and versatile devices based on these material systems. Of particular importance to applications involving light emission is identifying the most efficient excitation pathways of the rare earth dopant. Such a task is complicated by the presence of multiple rare earth environments often observed in such materials which have the potential to have drastically different relative excitation characteristics. Furthermore, due to the recent interest in dilute ferromagnetic semiconductors, the three systems studied have shown to all exhibit room temperature ferromagnetic behavior. This has led to several questions on the mechanism behind the interaction of ions which cause the ferromagnetism, and by which our spectroscopic techniques allow for unique investigations.
Author: Richard J. Molnar
Publisher:
ISBN:
Category : Gallium
Languages : en
Pages : 316
Get Book Here
Book Description
