Light emitting diodes (LEDs) are devices that are used in a myriad of applications, such as indicator lights in instruments, signage, illuminations, and communication. This graduate textbook covers all aspects of the technology and physics of infrared, visible-spectrum, and white light-emitting diodes (LEDs) made from III-V semiconductors. It reviews elementary properties of LEDs such as the electrical and optical characteristics. Exercises and illustrative examples reinforce the topics discussed.