A VLSI-compatible high-speed silicon photodetector for optical data link applications

A novel silicon photodetector suitable for high-speed, low-voltage operation at 780- to 850-nm wavelengths is reported. It consists of an interdigitated p-i-n detector fabricated on a silicon-on-insulator (SOI) substrate by using a standard bipolar process. Biased at 3.5 V, this device attains a -3-dB bandwidth in excess of 1 GHz at λ=840 nm. The dc responsivity measured at λ=840 nm on nonoptimized structures ranges from 0.05 to 0.09 A/W, depending on the finger shadowing factor. A new approach for improving the responsivity is proposed and quantitatively analyzed. The fabricated devices exhibit extremely low dark currents, small capacitance, large dynamic range, and no evidence of low-frequency gain. The overall performance and process compatibility of these photodetectors make them viable candidates for the fabrication of silicon monolithic receivers for fiber-optic data links