Low-Noise Avalanche Photodiode With Graded Junction in 0.15- $\mu{\rm m}$ CMOS Technology

This letter presents the experimental characterization and noise modeling of a CMOS avalanche photodiode with pwell/n-iso active junction fabricated in a 0.15-μm standard CMOS process. The device exhibits a remarkably low excess noise factor F = 6 at a gain M = 50 in the blue spectral region, and F = 12 at M = 50 in the near-infrared. Gain and noise characteristics are accurately predicted using Hayat dead-space model applied to a linearly graded junction doping profile.