Exploration of the epitaxial layer affecting behaviors of CMOS photodiodes

In this paper the method to deposit an epitaxial layer on the substrate of silicon-based image sensor to overcome the higher resposivity (A/W) at the infrared region due to energy gap, 1.12eV, of the silicon is explored. The measurement results demonstrate that the CMOS photodiode without epitaxial layer have the maximum responsivity at the infrared region but the photodiode with epitaxial layer reduces the responsivity at the infrared region efficiently. The model of the CMOS photodiode is utilized to analyze the characteristics of the epitaxial layer. The simulation results of the photo-responses of the epitaxial layers are also presented.