Photonic-electronic integration with polysilicon photonics in bulk CMOS

Here, I review the development of a polysilicon photonic platform that is optimized for integration with electronics fabricated on bulk silicon wafers. This platform enables large-scale monolithic integration of silicon photonics with microelectronics. A single-polysilicon deposition and lithography mask were used to simultaneously define the transistor gate, the low-loss waveguides, the depletion modulators, and the photodetectors. Several approaches to reduce optical scattering and mitigate defect state absorption are presented. Waveguide propagation loss as low as 3 dB/cm could be realized in front-end polysilicon with an end-of-line loss as low as 10 dB/cm at 1280nm. The defect state density could be enhanced to enable all-silicon, infrared photodetectors. The resulting microring resonant detectors exhibit over 20% quantum efficiency with 9.7 GHz bandwidth over a wide range of wavelengths. A complete photonic link has been demonstrated at 5 Gbps that transfers digital information from one bulk CMOS photonics chip to another.