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Author: Jack Lee Owsley (III)
Publisher:
ISBN:
Category : Electrical engineering
Languages : en
Pages : 44
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Book Description
In this thesis the characteristics of five bulk semi-insulated doped gallium nitride samples provided by Kyma Technologies, Inc were explored. The five GaN samples were grown on sapphire substrates by hydride vapor phase epitaxy (HVPE) and doped with different concentrations of iron, hydrogen, carbon, oxygen and silicon. The first step of characterization was measuring the optical absorption of all the samples using a UV-NIR fiber spectrometer. Through this procedure it was found that they all showed a strong absorption at 518 nm. Thus, time-resolved differential transmission measurements were conducted at this wavelength using the second harmonic generation (SHG) of a femtosecond ytterbium-doped fiber amplifier (YDFA), mode-locked laser. Relaxation times between 24 and 433 picoseconds were obtained. Finally, four point probe measurements were performed in the order to determine the bulk resistivity of the GaN samples. The measured values are within the order of 106[omega]*m for all samples.
Author: Jack Lee Owsley (III)
Publisher:
ISBN:
Category : Electrical engineering
Languages : en
Pages : 44
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Book Description
In this thesis the characteristics of five bulk semi-insulated doped gallium nitride samples provided by Kyma Technologies, Inc were explored. The five GaN samples were grown on sapphire substrates by hydride vapor phase epitaxy (HVPE) and doped with different concentrations of iron, hydrogen, carbon, oxygen and silicon. The first step of characterization was measuring the optical absorption of all the samples using a UV-NIR fiber spectrometer. Through this procedure it was found that they all showed a strong absorption at 518 nm. Thus, time-resolved differential transmission measurements were conducted at this wavelength using the second harmonic generation (SHG) of a femtosecond ytterbium-doped fiber amplifier (YDFA), mode-locked laser. Relaxation times between 24 and 433 picoseconds were obtained. Finally, four point probe measurements were performed in the order to determine the bulk resistivity of the GaN samples. The measured values are within the order of 106[omega]*m for all samples.
Author: Wang Rui
Publisher:
ISBN:
Category :
Languages : en
Pages : 130
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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: David M. Gibbons
Publisher:
ISBN:
Category :
Languages : en
Pages : 48
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GaN:Er is an attractive material for room temperature 1.54 pm luminescence enhancement devices for use in telecommunications because it does not experience thermal quenching at room temperature like Si:Er and can be electronically pumped. GaN:Er layers grown by molecular beam epitaxy (MBE) on single crystal substrates have shown excellent room temperature 1.54 [mu]m luminescence, but to integrate GaN:Er into microresonator devices it is necessary to grow a good quality GaN:Er film on an amorphous substrate. This thesis examines the optical properties and morphology of GaN:Er layers grown on Si3N4 and SiO2 substrates, and evaluates two microresonator devices with incorporated GaN:Er layers. GaN:Er layers grown by MBE on SiO2 and Si3N4 substrates were shown to give room temperature luminescence comparable to that of GaN:Er grown on (11 1)Si. GaN:Er layers grown on a buffered oxide etched Si3N4 substrate showed the best luminescence. The ability to grow good quality layers on amorphous substrates allows GaN:Er to be used in waveguide devices, the first of which studied was the microring resonator. Microring resonators were made by depositing a blanket GaN:Er layer on patterned Si3N4 microring structures. These structures were damaged, and transmission measurements were not possible. When looking at surface roughness measurements it appears that channel waveguide structures are unsuitable for GaN:Er grown on amorphous substrates, and so a ridge waveguide structure is proposed to lower this surface roughness scattering loss. A microcavity with a GaN:Er defect layer and a-Si/a-SiO2 stacks was fabricated and tested for luminescence enhancement. The refractive index of GaN:Er was determined by reflectance measurements to be 2.1. The layer was not of uniform thickness which led to a broad resonance peak, but a distortion of the spectrum including a lower luminescence at the 1517 nm peak and a higher luminescence at the 1557 nm peak were observed, which suggests enhancement by the microcavity.
Author: David Constantine Radulescu
Publisher:
ISBN:
Category : Doped semiconductors
Languages : en
Pages : 578
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Author: Alaa Ahmad Kawagy
Publisher:
ISBN:
Category : Epitaxy
Languages : en
Pages : 190
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The aim of this research is to investigate and characterize the quality of commercially obtained gallium nitride (GaN) on sapphire substrates that have been grown using hydride vapor phase epitaxy (HVPE). GaN substrates are the best choice for optoelectronic applications because of their physical and electrical properties. Even though HVPE GaN substrates are available at low-cost and create the opportunities for growth and production, these substrates suffer from large macro-scale defects on the surface of the substrate. In this research, four GaN on sapphire substrates were investigated in order to characterize the surface defects and, subsequently, understand their influence on homoepitaxial GaN growth. Two substrates were unintentionally doped (UID) GaN on sapphire, and the other two were semi-insulating (SI) GaN on sapphire which were doped with iron (Fe) in order to compensate the background doping inherent in GaN. Several characterization techniques were performed. Atomic force microscopy, scanning electron microscopy, and optical microscopy were performed to characterize the surface morphology. X-ray diffraction, cathodoluminescence, transmission measurements, and optical transmission electron microscopy were applied to study the bulk structural and optical properties. The investigation of the surface of GaN substrates exposed various defects that are associated with defects in the structure such as dislocations, as well as vacancies and point defects. The UID GaN substrates suffered from hexagonal V-shape pits with pits densities of approximately 107 and 108 cm-2, whereas, the SI GaN substrates exhibited much larger macro-scale pits with areal densities of about 102 cm-2. X-ray diffraction results were deconvoluted in order to characterize the screw and mixed (edge and screw) dislocation densities for the studied substrates. The UID substrates exhibited screw dislocation densities of 107 and 108 cm-2 and mixed dislocation densities of 109 and 1010 cm-2. The SI substrates, however, exhibit generally lower densities of dislocations of 109 and 108 cm-2 for screw and mixed, respectively. Cathodoluminescence measurements demonstrated interesting results for the UID and SI substrates with energies of 4 and 3.5 eV, respectively. The transmission measurements for the UID substrates showed that the bandgap energy was 3.39 eV.
Author: John Tarje Torvik
Publisher:
ISBN:
Category : Gallium nitride
Languages : en
Pages : 256
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Author: Chi Hang Ko
Publisher:
ISBN:
Category :
Languages : en
Pages : 170
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Book Description
Nitride based semiconductors have a unique combination of properties that make them especially suitable for many of the new challenges and applications of the twenty-first century, The group III nitride semiconductors, aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN) form a complete series of ternary alloys (InGaN, InAlN, and AlGaN) whose direct band gaps range from 1.9 to 6.2 eV. These compound semiconductors far exceed the physical properties of silicon, and GaN is the most dynamic of them. GaN is often referred to as the "final frontier of semiconductors", Its high thermal conductivity, high melting temperature, low dielectric constant and high breakdown voltage make it an attractive semiconductor for many electronic and optoelectronic devices such as light emitting diodes, laser diodes, radiation detectors, high power and high frequency devices capable of operating at high temperatures, and in hostile chemical environments and so on, GaN thin films, either intrinsic or doped with silicon or magnesium, were grown on silicon(lll) substrates with AIN buffer layers by Molecular Beam Epitaxy (MBE) under a broad range of growth parameters in this study. The samples were characterized using Filmetrics thin film analyzer, Atomic Force Microscopy (AFM), Photoluminescence Spectroscopy, hot probe, and four-point probe. Material growth began with deposition of a 0.3 monolayer (ML) of Al on the SiC 111) 7x7 surface leading to fully passivated Si(111) [square root]3x[square root]3-Al surface, on which AlN buffer layers and then the GaN layers were deposited. X-ray diffraction measurements indicated growth of single-crystalline hexagonal GaN(00l) while PL measurement demonstrated a peak position corresponding to bulk hexagonal GaN, Sample surface morphology, roughness, and resistivity showed a strong dependence on growth conditions and dopant types. The percent roughness/thickness on the GaN fIlms decreased linearly with increasing Si dopant temperature and increased exponentially to the first order with increasing Mg dopant temperature. P-type doping was achieved using Mg and the resistivity of both Si- and Mg-doped GaN samples showed an inverse linear relationship with the dopant temperatures.
Author: Stephen Pearton
Publisher: Elsevier
ISBN: 0128145226
Category : Technology & Engineering
Languages : en
Pages : 507
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Book Description
Gallium Oxide: Technology, Devices and Applications discusses the wide bandgap semiconductor and its promising applications in power electronics, solar blind UV detectors, and in extreme environment electronics. It also covers the fundamental science of gallium oxide, providing an in-depth look at the most relevant properties of this materials system. High quality bulk Ga2O3 is now commercially available from several sources and n-type epi structures are also coming onto the market. As researchers are focused on creating new complex structures, the book addresses the latest processing and synthesis methods. Chapters are designed to give readers a complete picture of the Ga2O3 field and the area of devices based on Ga2O3, from their theoretical simulation, to fabrication and application. Provides an overview of the advantages of the gallium oxide materials system, the advances in in bulk and epitaxial crystal growth, device design and processing Reviews the most relevant applications, including photodetectors, FETs, FINFETs, MOSFETs, sensors, catalytic applications, and more Addresses materials properties, including structural, mechanical, electrical, optical, surface and contact
Author: Masataka Higashiwaki
Publisher: Springer Nature
ISBN: 3030371530
Category : Technology & Engineering
Languages : en
Pages : 768
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This book provides comprehensive coverage of the new wide-bandgap semiconductor gallium oxide (Ga2O3). Ga2O3 has been attracting much attention due to its excellent materials properties. It features an extremely large bandgap of greater than 4.5 eV and availability of large-size, high-quality native substrates produced from melt-grown bulk single crystals. Ga2O3 is thus a rising star among ultra-wide-bandgap semiconductors and represents a key emerging research field for the worldwide semiconductor community. Expert chapters cover physical properties, synthesis, and state-of-the-art applications, including materials properties, growth techniques of melt-grown bulk single crystals and epitaxial thin films, and many types of devices. The book is an essential resource for academic and industry readers who have an interest in, or plan to start, a new R&D project related to Ga2O3.
Author: James D. Oliver
Publisher:
ISBN:
Category :
Languages : en
Pages : 66
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