Device-level optimization of sensitivity in high-speed separated absorption, grading charge, and multiplication avalanche photodiodes

Abstract

Device-level optimization of sensitivity in separated absorption, grading charge, and multiplication avalanche photodiodes (SAGCM APDs) has been performed. The impulse response was derived using the modified random path length (RPL) model for nonuniform electric field. The impact ionization in the charge layer was also taken into consideration with a modified RPL model based on the ionization coefficients deduced from Monte Carlo simulation. The bit error rate was calculated based on the derived impulse response, considering tunneling current, intersymbol interference, and bandwidth-limited gain. The bandwidth has significant effect on response, and sensitivity of APDs was optimized.