Light-Emitting Devices

Abstract

Photonic devices play an important role in a wide variety of applications in areas of optical communications, optical computing and interconnects, data transmission and signal processing, optical storage, sensors and optical imaging, solid-state lamps, and displays. Recent advances in III-V compound semiconductor growth and processing technologies have enabled these applications to become a reality. As a result, various photonic devices such as light-emitting diodes (LEDs), laser diodes (LDs), modulators, and photodetectors using III-V semiconductors have been developed for a wide variety of commercial applications. The LEDs are p-n junction diodes made from III-V and II-VI compound semiconductors that emit incoherent light under forward-bias conditions, while the LDs are p-n junction diodes with higher doping densities that emit coherent light for use in space and fiber-optic communications and data transmission, laser printers, CDs, and DVDs. In addition to high performance, low cost, and reliability, another factor in favor of LEDs is their compatibility with modern electronic devices as well as the increasingly important applications in visual displays. Low power, low operating voltage, small size, fast switching speed, and long life are some attractive features of LEDs. It is noted that the manufacturing technology for LEDs is compatible with silicon-integrated circuit technology. Depending on the complexity of visual tasks, LEDs are being used as solid-state lamps, symbolic and picture displays, data transmission, and in optical communications. LEDs coupled with silicon photodiodes can be used as optically isolated switches and sensing elements.With the technology breakthrough and cost reduction, the flat panel picture display using LEDs will soon become a reality for commercial applications. In this chapter the basic device physics and structures, operation principles, and general characteristics of various LEDs and LDs fabricated from III-V and II-VI compound semiconductors are discussed.