We have measured the dark current (Id) and noise equivalent power (NEP) of four large-area (~0.8 cm2) avalanche photodiodes (APD) to determine their sensitivity limit for detecting weak optical communication signals. We found that from room temperature down to about -10°C the Id decreased by one-half for every 8-deg drop in temperature and the NEP decreased by one-half for every 16-deg drop in temperature. Below this temperature, the NEP leveled off at somewhat less than 5 pW in a 100-kHz bandwidth. We describe the measurement technique, present an analysis of the data, and discuss the statistical properties of these APDs according to the model developed by McIntyre et al.
"Measurements of the operating characteristics of a large-area avalanche photodiode," Optical Engineering 31(1), (1 January 1992). https://doi.org/10.1117/12.56040