Solid state electronics is undergoing rapid changes driven by heteroepitaxy, lithography, and new device concepts. While ten years ago Si was the material of choice in solid state electronics, now Ga As, In Ga As , Al As, In P, Ge, etc. have all become quite important. The advent of semiconductor lasers and integrated optoelectronic circuits has led to a flurry of activities in compound semiconductors. Additionally, the remarkable advances in the thin film epitaxy have allowed active semiconductor devices with sub-three-dimensional properties and built-in controlled biaxial strain due to lattice mismatch. This book addresses three main areas of interest: i) electronic and optical properties oflow- dimensional semiconductor materials; ii) principal physics of quantum electronic devices, iii) principal physics of quantum optical devices. These areas will provide readers with an intimate knowledge of the new material properties on which novel solid state electronic devices such as quantum diode, and small size transistor, high electron mobility transistor are based, leading to the very front of the development of material and device research. The link between basic physics on which the real devices are based and the output from the real devices is closely observed in the book. Chapter 1 Elemental and compound semicond uctors 1. 1 Crystalline nat ure of solids The intrinsic property of a crystal is that the environment around a given atom or group of atoms is exactly the same as the environment around another atom or similar group of atoms.