This book sets out the fundamental quantum processes that are important in the physics and technology of semiconductors in a relatively informal style that graduate students will find very attractive‎.‎ The fifth edition includes new chapters that expand the coverage of semiconductor physics relevant to its accompanying technology‎.‎ One of the problems encountered in high‎-power transistors is the excessive production of phonons and the first new chapter examines the hot‎-phonon phenomenon and the lifetime of polar optical phonons in the nitrides‎.‎ In the burgeoning field of spintronics a crucial parameter is the lifetime of a spin‎-polarised electron gas‎,‎ and this is treated in detail in the second of the new chapters‎.‎ The third new chapter moves from the treatment of bulk properties to the unavoidable effects of the spatial limitation of the semiconductor‎,‎ and to the influence of surface states and the pinning of the Fermi level‎.‎ As with previous editions the text restricts its attention to bulk semiconductors‎.‎ The account progresses from quantum processes describable by density matrices‎,‎ through the semi‎-classical Boltzmann equation and its solutions‎,‎ to the drift‎-diffusion description of space‎-charge waves‎,‎ the latter appearing in the contexts of negative differential resistance‎,‎ acoustoelectric and recombination instabilities‎.‎ Besides being a useful reference for workers in the field‎,‎ this book will be a valuable text for graduate courses‎.‎