The unique materials properties of GaN-based semiconductors have stimulated a great deal of interest in research and development regarding nitride materials growth and optoelectronic and nitride-based electronic devices. High electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown field, and low thermal impedance of GaN-based films grown over SiC or bulk AlN substrates make nitride-based electronic devices very promising. The chemical inertness of nitrides is another key property.This volume, written by experts on different aspects of nitride technology, addresses the entire spectrum of issues related to nitride materials and devices, and it will be useful for technologists, scientists, engineers, and graduate students who are working on wide bandgap materials and devices. The book can also be used as a supplementary text for graduate courses on wide bandgap semiconductor technology.
This book on gallium nitride (GaN) and associated materials focuses on advances in basic science, as well as the rapidly maturing technologies involving blue/green light emitters, detectors and high-power electronics. A highlight is a report on wide-bandgap semiconductor research done in Europe. Also reported is the commercialization of a laser operating at 405nm wavelength with a 4000-hour device lifetime. At 450nm emission wavelength, significant reductions in lifetime were found, and are believed to arise from nonideal properties of the InGaN alloy used in the active layer of the device. Additional topics include: the significant success of transistors for microwave applications; improvements in the epitaxy of GaN, using both selective area growth techniques (lateral epitaxy overgrowth) and introducing low-temperature intralayers in the films; advances in both molecular beam epitaxy and metal-organic vapor phase epitaxy, including several studies of quantum dot formation in strained alloys and improvements in hydride vapor phase epitaxy, particularly for providing very thick films.
This dissertation employs doping to investigate basic gallium nitride (GaN) crystal properties and to solve challenges of the hydride vapour phase epitaxy (HVPE) growth process. Whereas the first chapter is a short introduction to the history of the GaN single crystal growth, the 2nd chapter introduces to current crystal growth techniques, discusses properties of the GaN material system and the resulting influence on the applicable crystal growth techniques. HVPE, as a vapour phase epitaxy crystal growth method will be explained in greater detail, with focus on the used vertical reactor and its capabilities for doping. The 3rd chapter then focusses on point defects in GaN, specifically on intentionally introduced extrinsic point defects used for doping purposes, i.e. to achieve p-type, n-type or semi-insulating behaviour. Different dopants will be reviewed before the diffusion of point defects in a solid will be discussed. The in-situ introduction of iron, manganese, and carbon during crystal growth is employed in chapter 4 to compensate the unintentional doping (UID) of the GaN crystals, and therefore to achieve truly semi-insulating behaviour of the HVPE GaN. However the focus of this chapter lies on the characterisation of the pyroelectric coefficient (p), as semi-insulating properties are a necessary requirement for the applied Sharp-Garn measurement method. The creation of tensile stress due to in-situ silicon doping during GaN crystal growth is the topic of the 5th chapter. The tensile stress generation effect will be reproduced and the strain inside the crystal will be monitored ex-situ employing Raman spectroscopy. The n-type doping is achieved by using a vapour phase doping line and a process is developed to hinder the tensile strain generation effect. The 6th chapter concentrates on the delivery of the doping precursor via a solid state doping line, a newly developed doping method. Similar to chapter 5, the doping line is characterised carefully before the germanium doping is employed to the GaN growth. The focus lies on the homogeneity of the germanium doping and it is compared compared to the silicon doping and the vapour phase doping line. Benefits and drawbacks are discussed in conjunction with the obtained results. The germanium doping via solid state doping line is applied to the HVPE GaN growth process to measure accurately growth process related properties unique to the applied set of GaN growth parameters.
The field of organic optical materials is rapidly growing, and advances are being made both in attaining a deeper understanding of device phenomena and in designing improved materials for thin films, fibers and waveguides. This book offers an interdisciplinary discussion of research on electronic and photonic devices made with organic and polymeric materials. The 1999 MRS Spring Meeting was highlighted by several major advances in fields ranging from nonlinear absorbers and electro-optic polymers, to photorefractive polymers, organic transistors and electroluminescent materials and devices for displays. This book highlights developments in materials chemistry and physics relevant to such devices and strikes a balance between basic science and technology. Topics include: nonlinear optical materials; photorefractive polymers; and electronic and light-emitting materials.
Optical methods for investigating semiconductors and the theoretical description of optical processes have always been an important part of semiconductor physics. Only the emphasis placed on different materials changes with time. Here, a large number of papers are devoted to quantum dots, presenting the theory, spectroscopic investigation and methods of producing such structures. Another major part of the book reflects the growing interest in diluted semiconductors and II-IV nanosystems in general. There are also discussions of the fascinating field of photonic crystals. `Classical' low dimensional systems, such as GsAs/GaAlAs quantum wells and heterostructures, still make up a significant part of the results presented, and they also serve as model systems for new phenomena. New materials are being sought, and new experimental techniques are coming on stream, in particular the combination of different spectroscopic modalities.
This book contains the proceedings of two symposia - 'Integration of Dissimilar Materials in Micro- and Optoelectronics' and 'III-V and SiGe Group IV Device/IC Processing Challenges for Commercial Applications'. The publication stems from the desire to achieve new levels of device functionality and higher levels of performance via integration of devices based on dissimilar semiconductors, where the constraint of lattice-matching on the breadth of attainable devices can be reduced. It covers fundamental topics germane to integration of a wide range of dissimilar materials spanning wide-bandgap III-V nitrides, III-V/Si integration, II-VI and II-VI/III-V compounds, heterovalent structures, oxides, photonic bandgap structures and others. Topics such as compliancy, dislocation control, selective area growth, bonding methodologies, etc. are featured. It also addresses processing issues in the manufacturing of III-V and Si-based heterostructures for commercial products. Here, the success enjoyed by silicon germanium technology is contrasted by the promise of silicon-carbon alloys which have opportunities and challenges for the new generation of process developers.
Luminescent materials are of interest to members of the spectroscopic, basic science, engineering and display communities. This book presents a wide range of topics from basic research of fluorescence to applications-driven research on phosphors and scintillators. Papers on various luminescent, fluorescent or phosphorescent mechanisms arising in inorganic crystalline and noncrystalline materials, as well as in organic materials, are featured. The use of fluorescence as a sensing technique has emerged as a sensitive and noninvasive way to probe biological activity or measure physical phenomena. To that end, progress in understanding fluorescence, the development of novel applications of fluorescence, and novel material structures are addressed. Phosphors for the emerging flat-panel-display industry are also highlighted. Topics include: inorganic phosphors; thin-film phosphors; synthesis, processing and characterization; mechanisms and defects; organic luminescence and theory and luminescence sensors.
Liquid crystal (LC) materials and devices play a central role in numerous established and emerging technologies. This book focuses on several large areas of research including polymer-dispersed liquid crystal technology and twisted smectic materials and applications, as well as nontraditional LC materials and applications. Various aspects of liquid crystal composite technology are featured. Of note is the work concentrating on the use of holography to imprint information into thin films of these systems. Three different approaches for employing holography with liquid crystal materials are discussed. In the ferroelectric liquid crystal arena, the intricacies of different chiral smectic-C architectures are described using detailed X-ray structural experiments on freestanding films. The differences between a molecule and a phase are explored. A number of nondisplay applications using this class of materials are presented and include topics such as adaptive optics, real-time holography and fiber-to-fiber interconnects. Also discussed are glass-forming liquid crystalline films and their ability to polarize photoluminescent emission, their utility in the fabrication of mid-wavelength infrared polarizers, and their utility in the fabrication of bistable electro-optical elements and broadband reflectors.
