Since the early 1990s when highly efficient gallium nitride blue and ultraviolet LEDs and laser diodes were first demonstrated, the world market for such devices has rapidly expanded. Based on its outstanding properties, including a wide energy band gap, high thermal conductivity, and high electron drift velocity, GaN is uniquely suited for many novel devices including solar-blind UV light detectors, high power microwave transistors, and cold cathode electron emitters. The widening range of applications are generating an 80% p.a. growth in R&D. This book covers the basic physical and chemical properties, surveys existing processing technology, and presents summaries of the current state-of-the-art of devices.This book is an excellent reference for authoritative reviews of all aspects relevant to current devices, and for developing new devices.