CMOS-compatible planar silicon waveguide-grating-coupler photodetectors fabricated on silicon-on-insulator (SOI) substrates

We report planar silicon interdigitated p-i-n photodiodes with waveguide-grating couplers fabricated on silicon-on-insulator (SOI) substrates. The devices were fabricated in standard CMOS technology on 200-nm-thick SOI wafers with no additional fabrication steps. A waveguide-grating coupler with a period of 265 nm increased the quantum efficiency by a factor of four compared to a photodiode without a coupler. The dark current was 10 pA at -3-V bias and the bandwidth was 4.1 GHz (RC limited).