Power semiconductor devices are attracting increasing attention as key components in a variety of power electronic systems. The major applications of power devices include power supplies, motor controls, renewable energy, transportation, telecommunications, heating, robotics, and electric utility transmission/distribution. The utilization of semiconductor power devices in these systems can enable significant energy savings, increased conservation of fossil fuels, and reduced environmental pollution.

Power electronics has gained renewed attention in the past decade due to the emergence of several new markets, including converters for photovoltaic and fuel cells, converters and inverters for electric vehicles (EVs) and hybrid-electric vehicles (HEVs), and controls for smart electric utility distribution grids. Currently, semiconductor power devices are one of the key enablers for global energy savings and electric power management in the future.

Silicon power devices have improved significantly over the past several decades, but these devices are now approaching performance limits imposed by the fundamental material properties of silicon, and further progress can only be made by migrating to more robust semiconductors. Silicon carbide (SiC) is a wide-bandgap semiconductor with superior physical and electrical properties that can serve as the basis for the high-voltage, low-loss power electronics of the future.

SiC is a IV–IV compound semiconductor with a bandgap of 2.3–3.3 eV (depending on the crystal structure, or polytype). It exhibits about 10 times higher breakdown electric field strength and 3 times higher thermal conductivity than silicon, making it especially attractive for high-power and high-temperature devices. For example, the on-state resistance of SiC power devices is orders-of-magnitude lower than that of silicon devices at a given blocking voltage, leading to much higher efficiency in electric power conversion. The wide bandgap and high thermal stability make it possible to operate certain types of SiC devices at junction temperatures of 300 °C or higher for indefinite periods without measurable degradation. Among wide-bandgap semiconductors, SiC is exceptional because it can be easily doped either p-type or n-type over a wide range, more than five orders-of-magnitude. In addition, SiC is the only compound semiconductor whose native oxide is SiO₂, the same insulator as silicon. This makes it possible to fabricate the entire family of MOS-based (metal-oxide-semiconductor) electronic devices in SiC.

Since the 1980s, sustained efforts have been directed toward developing SiC material and device technology. Based on a number of breakthroughs in the 1980s and 1990s, SiC Schottky barrier diodes (SBDs) were released as commercial products in 2001. The market for SiC SBDs has grown rapidly over the last several years. SBDs are employed in a variety of power systems, including switch-mode power supplies, photovoltaic converters, air conditioners, and motor controls for elevators and subways. Commercial production of SiC power switching devices, primarily JFETs (junction field-effect transistors) and MOSFETs (metal-oxide-semiconductor field-effect transistors), began in 2006–2010. These devices are well accepted by the markets and many industries are now taking advantage of the benefits of SiC power switches. As an example, the volume and weight of a power supply or inverter can be reduced by a factor of 4–10, depending on the extent to which SiC components are employed. In addition to the size and weight reduction, there is also a substantial reduction in power dissipation, leading to improved efficiency in electric power conversion systems due to the use of SiC components.

In recent years, the SiC professional community has grown rapidly in both academia and industry. More and more companies are developing SiC wafer and/or device manufacturing capabilities and the population of young scientists and engineers is increasing. Unfortunately, very few textbooks are yet available that cover the broad spectrum of SiC technology from materials to devices to applications. Thus, those scientists, engineers, and graduate students are potential readers of this text. The authors hope this book will be timely and beneficial for such readers, and will enable them to rapidly acquire the essential knowledge to practice in this field. Since this book covers both fundamentals and advanced concepts, a minimum knowledge of semiconductor physics and devices is assumed, but a graduate student majoring in material science or electrical engineering will have no difficulty in reading this book.

The main topics described in this book include SiC physical properties, bulk and epitaxial growth, characterization of electrical and optical properties, extended and point defects, device processing, design concepts of power rectifiers and switching devices, physics and features of unipolar/bipolar devices, breakdown phenomena, high-frequency and high-temperature devices, and system applications of SiC devices. Both fundamental concepts and state-of-art implementations are presented. In particular, we try to explain all the subjects with an in-depth treatment, including basic physics, present understanding, unaddressed issues, and future challenges.

Finally the authors acknowledge a number of colleagues and pioneers in this field, especially Prof. W. J. Choyke (University of Pittsburgh), Emeritus Prof. H. Matsunami (Kyoto University), the late Dr G. Pensl (University of Erlangen-Nürnberg), Prof. E. Janzén (Linköping University), and Dr J. W. Palmour (Cree) for their valuable contributions to the field and to our understanding. We also thank Mr. James Murphy and Ms. Clarissa Lim of Wiley for their guidance and patience. At last, we thank our family for their kind encouragement and support in writing this book. Without their support and understanding, this book would not have been published.

Kyoto and West Lafayette, September 2013
Tsunenobu Kimoto
James A. Cooper