High speed polysilicon CMOS photodetector for telecom and datacom
Absorption by mid bandgap states in polysilicon or heavily implanted silicon has been previously utilized to implement guided wave infrared photodetectors in CMOS compatible photonic platforms. Here, we demonstrate a resonant guided wave photodetector based on the polysilicon layer that is used for the transistor gate in a microelectronic SOI CMOS process without any change to the foundry process flow "zero change" CMOS) Through a combination of doping mask layers, a lateral pn junction diode in the polysilicon is demonstrated with a strong electric field to enable efficient photo carrier extraction and high speed operation. This photodetector has a responsivity of more than 0.14 A/W from 1300 to 1600 nm, a 10 GHz bandwidth, and 80 nA dark current at 15 V reverse bias.