Monte Carlo simulation of gain, noise, and speed of low-noise and high-speed avalanche photodiodes

A Monte Carlo simulation model is developed. The low-noise behavior of AlGaAs/GaAs avalanche photodiodes (APDs) is successfully simulated and is explained as spatial localization of impact ionization events. The noise is sensitive to initial carrier energy and we point out that energetic and hot electrons should be distinguished. This model also successfully explains the measured exponential gain curve and “noiseless” behavior of HgCdTe APDs. I demonstrate that this model can aid the design of high-speed InGaAs/InAlAs APDs. Model parameters are constrained with low-temperature measurements of APD gain and noise in this work. I have also suggested a new shot noise suppression mechanism associated with multiplication gain.