The fundamentals of semiconductors encompass a broad array of principles, phenomena, and applications that are critical to modern electronics. This book delves deeply into the intrinsic properties of semiconductors, beginning with their crystal structure and the formation of energy bands. Understanding the energy bands is essential as they define the behavior of charge carriers-electrons and holes-that facilitate electrical conduction. The book also covers intrinsic semiconductors, which are pure forms of the material, and extrinsic semiconductors, where impurities or doping elements are introduced to modify electrical properties. The book also explores various semiconductor devices, each leveraging the fundamental properties of the materials to perform specific functions. Diodes, for instance, exploit the p-n junction. Understanding the quantum behavior of electrons in semiconductors is crucial for the development of modern devices such as quantum dots, which have applications in quantum computing and advanced imaging techniques.