This text covers the various material properties of bulk GaAs and related materials, and aspects of the physics of artificial semiconductor micro-structures - such as quantum wells and superlattices - made of these materials. A complete set of the material properties are considered in this book. They are: structural properties; thermal properties; elastic and lattice vibronic properties; collective effects and some response characteristics; electronic energy-band structure and consequences; optical, elasto-optic, and electro-optic properties and carrier transport properties. This work attempts to summarize, in graphical and tabular forms, most of the important theoretical and experimental results on these material properties. It contains a large number of references useful for further study. This book will be of interest to graduate students, scientists and engineers working on semiconductors.