Advances in chip-integrated silicon-germanium photodetectors

Optical communication links call upon higher transmission speeds and lower energy consumption while going down to shorter and shorter interconnect spans. This scaling arguably requires novel chip-scale components with high optoelectrical performances realized at a reduced price and high yield. Silicon photonics technology delivers such devices on group-IV semiconductor chips by leveraging mature fabrication processes adopted from modern microelectronics. In this environment, optical photodetectors, devices that transform optical signals into electrical ones, are integral building blocks for future on-chip communication links and interconnects. This chapter reviews recent advances in monolithically integrated silicon-germanium optical photodetectors. The chapter traces the progress and development in optical photodetectors based on two dominant group-IV elemental semiconductors, silicon, and germanium, including material processing, integration, and a variety of demonstrated device designs and profound light detection strategies.