Preface

Since the invention of the solid-state transistors, the semiconductor technologies have advanced at an exponential pace and become the foundation for numerous industries, e.g. computing, communication, consumer electronics, autonomous systems, and defense. Guided by Moore's law, the scaling of transistors has provided new generations of chips every one to two years, with ever-increasing density and better performance. Today, silicon transistors are approaching some fundamental limits of dimensional scaling. The semiconductor industry has also transformed through several phases and foundational technologies. The emergence of Internet of Things (IoT), big data, artificial intelligence (AI), and quantum computing has created new opportunities for advanced semiconductor technologies. The complementary metal-oxide-semiconductor (CMOS) technology dominates the semiconductor industry today, but there are numerous technologies and active research beyond conventional CMOS. Although semiconductors are often associated with high-performance computing chips such as central processing unit (CPU) and graphics processing unit (GPU), there is a wide range of applications beyond computing for semiconductor products, e.g. sensors, displays, and power electronics. Silicon (Si) is the most important semiconductor, but the semiconductor research also covers a variety of materials, e.g. germanium (Ge), III-V compounds, organic materials, carbon nanotube, 2D materials, magnetic materials, and topological materials.

This book is a collection of articles reviewing advanced semiconductor technologies beyond conventional Si CMOS for various applications. These articles written by the experts in the fields can be read independent of each other. The variety of topics reflects the breadth of the semiconductor R&D and applications today, but these articles only cover a very small fraction of semiconductor technologies.

With the transistor scaling approaching the fundamental limits, heterogeneous integration is a promising direction to sustain the improvement of performance and functionalities without relying on reducing transistor sizes. Chapter 1, "Heterogeneous Integration at Scale," provides a comprehensive review of technologies, design/architecture considerations, reliability issues, applications, and future directions of large-scale heterogeneous integration.

While technology innovation has been a primary driver for the semiconductor industry, the future of semiconductor systems will increasingly resort to novel computing paradigms. Chapter 2, "Hyperdimensional Computing: An Algebra for Computing with Vectors," presents an example of entirely new ways of computing inspired by the information processing in the brain. Instead of traditional model of computing with numbers, hyperdimensional (HD) computing encodes information in a holographic representation with wide vectors and unique operations. HD computing is extremely robust against noise, matches well with 3D circuits, and is uniquely suitable to process a variety of sensory signals without interference with each other.

The majority of semiconductor chips are digital circuits; however, analog and mixed-signal circuits are crucially important. The physical world is analog; therefore, analog circuits are always needed to connect digital chips with real world, e.g. sensory data, power management, and communication. Although digital circuit design is highly automated, analog circuit design still relies on manual effort. Chapter 3, "CAD for Analog/Mixed-Signal Integrated Circuits," reviews the progress toward automated computer-aided design (CAD) of analog and mixed-signal circuits.

Modern computers are built based on the von Neumann architecture with separate logic/computing units and memory/storage units. Emerging memory devices not only provide new technologies to improve memory systems but also enable novel computing architectures, e.g. in-memory computing. One of the most promising emerging memories is based on magnetic materials and properties. Chapters 4 and 5 focus on a so-called magnetoelectric field effect transistor (MEFET) based on the programming of the polarization in a 2D semiconductor channel with large spin-orbit coupling, via the proximity effect of a magnetoelectric gate. Chapter 4, "Magnetoelectric Transistor Devices and Circuits with Steering Logic," presents various logic gate designs based on a one-source two-drain MEFET configured with a steering function. Chapter 5, "Nonvolatile Memory Based Architectures Using Magnetoelectric FETs," describes MEFET memory designs with the performance and size suitable to fulfill the application space between static random-access-memory (SRAM) and dynamic random-access-memory (DRAM).

Novel materials beyond Si, Ge, and III-V compounds may enable new semiconductor products and applications. Among them, organic semiconductors are promising materials for low-cost, flexible, and bio-compatible electronics. Chapter 6, "Organic Electronics," discusses the opportunities of organic semiconductors for large-area flexible electronics, including organic light-emitting diode (OLED), organic displays, organic solar cells, and thin-film transistors. Chapter 7, "Active-Matrix Electroluminescent Displays," delves into the details of flat panel electroluminescent displays based on light-emitting diodes (LEDs) that have been utilized in a wide range of applications including smart phones, tablets, laptops, and TVs. Various underlying LED technologies, associated circuits, and design considerations are reviewed. Another interesting application of organic materials is memory. Chapter 8, "Organic and Macromolecular Memory - Nanocomposite Bistable Memory Devices," discusses the mechanisms, characteristics, and current status of organic memories. One of the advantages of organic materials is their low-cost processing and the potential to stack up multiple layers. Chapter 9, "Next Generation of High-Performance Printed Flexible Electronics," summarizes different printing technologies for flexible electronics, showcases the state-of-the-art printed flexible electronic circuits, and discusses the challenges and future directions of large-scale cost-effective printed electronics. The vision of integrating electronic components onto polymer foils leads to the flexible electronics version of systems-on-chip (SoC), known as systems-in-foil (SiF). A wide range of applications can benefit from SiF, e.g. smart labels, intelligent electronic skin, and implanted devices. Chapter 10 "Hybrid Systems-in-Foil" reviews the opportunities of SiF and challenges in materials, integration, and testing.

The electronic systems need an interface with the physical world. Semiconductor chips rely on sensors to "see," "hear," and "smell." Optical sensing is utilized in a wide range of applications, e.g. camera, fiber optics and communication, light source and laser, data storage, medical monitoring and diagnostics, and manufacturing. Chapter 11, "Optical Detectors," reviews the photodiodes based on Si, III-V, and emerging materials as the essential components for highly sensitive detectors for a broad spectrum of wavelengths. Chapter 12, "Environmental Sensing," covers comprehensively different air pollution sources, air quality metrics, and various sensing approaches for particulate matters and volatile organic compounds. The advancement of semiconductor technologies contributes to the miniaturization of the sensing equipment and the improvement of their performance.

Unlike computer chips operating with very low voltage and current, power electronics handle very high voltage (e.g. thousands of volt or higher) and current required to operate machinery, vehicles, appliances, etc. Special device designs and unique material properties are required to sustain such high voltage and current in semiconductor chips. Chapter 13, "Insulated Gate Bipolar Transistors (IGBTs)," reviews an important high-power device known as Si insulated gate bipolar transistors (IGBTs). IGBT not only dominates power electronics today but also continues to be innovated for further gains in power density and efficiency. At the same time, significant progress has been made on wide bandgap semiconductors. Chapter 14, "III-V and Wide Bandgap," reviews promising materials (e.g. diamond, GaN) and their applications in high-frequency power conversion and high-temperature electronics. While wide bandgap power modules may be combined with Si-based control circuits in near-term solutions, considerable effort is made to advance integrated circuits based on wide bandgap semiconductors. Chapter 15, "SiC MOSFETs," reviews SiC-based power semiconductor devices including diodes and transistors. SiC is well positioned to fulfill the requirements of power...