Germanium Gate PhotoMOSFET Integrated to Silicon Photonics

This paper presents a novel germanium gated NMOS phototransistor integrated on a silicon photonics platform on silicon-on-insulator (SOI) substrate. The phototransistor is fabricated with a modified NMOS process flow, with germanium which is recrystallized using rapid melt growth during the source/drain activation anneal step. The resulting device, with 1-μm channel length, and 8-μm channel width, demonstrates a responsivity of over 18 A/W at 1550 nm with 583 nW of incident light. By increasing the incident power to 912 μW, the device operates at 2.5 GHz. Miniaturization is expected to improve both responsivity and speed in future devices.