Area-dependent photodetection frequency response characterization of silicon avalanche photodetectors fabricated with standard CMOS technology

We investigate the area-dependent characteristics of photodetection frequency responses of 850-nm silicon avalanche photodetectors (APDs) fabricated with standard complementary metal-oxide-semiconductor (CMOS) technology. CMOS-compatible APDs (CMOS-APDs) based on a p⁺ /n-well junction with four different device areas are used for the investigation, and we identify factors that influence photodetection frequency responses with the goal of achieving optimal photodetection bandwidth performance. Their current-voltage characteristics, electrical reflection coefficients, and photodetection frequency responses are measured, and the characteristics of the CMOS-APD photodetection frequency responses are analyzed using equivalent circuit models. From this, it is clarified how the four different factors of photogenerated-carrier transit time, device RC time constant, inductive-peaking effect, and parasitics contribute to the photodetection frequency responses and how their contribution changes with device areas. Among the four types of CMOS-APDs investigated in this study, the 10 \times \hbox{10}\ \mu\hbox{m} ² CMOS-APD has the largest 3-dB photodetection bandwidth of 7.6 GHz.