Advanced technologies such as autonomous driving, cloud computing, Internet of Things, and artificial intelligence have considerably increased data demand. Real-time interactions further drive the development of high-speed, high-capacity networks. Advancements in communication systems depend on developing high-speed optoelectronic devices. Optical communication systems are rapidly evolving, with data rates advancing from 800 Gbps to 1.6 Tbps and beyond, driven by the development of high-performance photodetectors, high-speed modulators, and advanced RF devices. Avalanche photodetectors (APDs) are used in long-distance applications owing to their high internal gain and responsivity. This paper reviews the structural designs of APDs based on various materials for high-speed communication and provides an outlook on developing APDs based on advanced materials.