High-speed III-V based avalanche photodiodes for optical communications—the forefront and expanding applications

Avalanche photodiodes (APDs), i.e., semiconductor devices, which convert and amplify optical signals into electrical signals, are used for optical communications and for imaging and medical applications. The major requirements for APDs in optical communications are high-speed operation for high data rates and high-sensitivity operation for extending the transmission reach. This paper overviews the achievements of high-speed APDs for 100-Gbit/s optical communications, focusing on III-V material systems, which are advantageous in terms of band engineering. The outlook for APDs in future optical communications is also described.