Light emitting diodes (LEDs) are already used in traffic signals, signage lighting, and automotive applications. However, its ultimate goal is to replace traditional illumination through LED lamps since LED lighting significantly reduces energy consumption and cuts down on carbon-dioxide emission. Despite dramatic advances in LED technologies (e.g., growth, doping and processing technologies), however, there remain critical issues for further improvements yet to be achieved for the realization of solid-state lighting. This book aims to provide the readers with some contemporary LED issues, which have not been comprehensively discussed in the published books and, on which the performance of LEDs is seriously dependent. For example, most importantly, there must be a breakthrough in the growth of high-quality nitride semiconductor epitaxial layers with a low density of dislocations, in particular, in the growth of Al-rich and and In-rich GaN-based semiconductors. The materials quality is directly dependent on the substrates used, such as sapphire, Si, etc. In addition, efficiency droop, growth on different orientations and polarization are also important. Chip processing and packaging technologies are key issues. This book presents a comprehensive review of contemporary LED issues. Given the interest and importance of future research in nitride semiconducting materials and solid state lighting applications, the contents are very timely. The book is composed of chapters written by leading researchers in III-nitride semiconducting materials and device technology. This book will be of interest to scientists and engineers working on LEDs for lighting applications. Postgraduate researchers working on LEDs will also benefit from the issues this book provides.

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.