Research of different structure integrated photodetectors in standard CMOS technology

Abstract

Three kinds of structure photodetectors, N⁺/N-Well/P-Substrate, P⁺/N-Well/P-Substrate and finger N⁺/N-Well/P-Substrate, have been fabricated in CSMC 0.5μm CMOS process. The characteristics of different photodetectors are comparatively tested. The N⁺/N-Well/P-Substrate photodetector is choosed for construction of novel Spice model and fabrication of OEIC chip, considered about both high responsivity and good response speed. A novel Spice model of photodetector is introduced for compatible-design of OEIC. At 780nm and 2.5V reverse bias, the simulated responsivity based on the Spice model is 0.251A/W, close to the measured value 0.253A/W. Finally, a full CMOS monolithic OEIC is successfully accomplished with a gain of 38.1mV/μW in 780nm for optical-disc signal pickup.