Integrated silicon optical receiver with avalanche photodiode

An optical receiver consisting of an avalanche photodiode integrated with a trans-impedance amplifier is reported. The optical receiver was fabricated on a 2 μm thick SOI substrate in a 130nm unmodified CMOS process flow. The unity gain external quantum efficiency of the photodetectors was ∼10% at 850 nm. Optimum sensitivity was achieved for an avalanche gain M=8. This gain accounted for 5 dB improvement in receiver sensitivity at 2 Gbit/s. Operation at 8 Gbit/s was achieved only when the photodetector was biased in the avalanche gain regime.