Monte Carlo Simulation of Photoresponse in Silicon Photodiodes with p-n-Junction and p-i-n-Structure

Abstract

Numerical modeling of semiconductor photodiodes’ electrical characteristics is an important task at the stage of their development and design. In this regard, it should be noted that one of the most promising methods that can be used for this purpose is the ensemble Monte Carlo method, which allows including, along with the dominant mechanisms of charge carriers’ scattering in the device structure, also the processes of impact ionization, which is very important for adequate modeling of a wide class of silicon photodiodes operating in the reverse bias mode. The aim of the work was to study the influence of the impact ionization process on the electrical characteristics of silicon photodiodes with a p-n-junction and a p-i-n-structure operating in the reverse bias mode under the influence of picosecond pulses of visible radiation. Using selfconsistent simulation by the ensemble Monte Carlo method, the electron ionization coefficient in bulk silicon at a crystal lattice temperature of 300 K was calculated and compared with known experimental data. Photoresponse in silicon submicron photodiodes with a p-n-junction and photodiodes with a p-i-n-structure was calculated for different thicknesses of the undoped i-region. It was shown that use of simple models similar to the Keldysh model with constant values of the threshold energy and other parameters for calculating the rate of the impact ionization process did not allow obtaining values of the ionization coefficient matched with experimental data in a wide range of electric field strengths. This result raises the question on the adequacy of the device structures’ electrical characteristics modeling with a non-uniform electric field when using such simple impact ionization models.