Abstract:An avalanche photodiode (APD) with p+/n-well diode structure was proposed based on 0.35μm CMOS process, and p well guard ring (GR) was used to prevent premature breakdown. The properties of the proposed APD including the electric field intensity, the response rate, quantum efficiency and frequency characteristic were simulated and analyzed. The results show that: with p well GR, this premature edge breakdown is alleviated and sufficient avalanche gain is obtained, the avalanche breakdown voltage of CMOS APD is 9.2V, the responsivity is 0.65A/W, the maximum internal quantum efficiency is about 90%, the detected signal bandwidth can reach 6.3GHZ, and the working wavelength is from 400~900nm.