Abstract: In CMOS image sensors, forming a barrier with a Delta structure (Delta-doping) on the surface can effectively resolve the issues of performance changes in traditional CMOS image sensors under irradiation environment. The width and height parameters of the barrier directly affect the dark current on the surface of the CMOS image sensor as well as the efficiency of surface signal detection. This paper assumes that the total energy of electrons and the cross-sectional direction of tunneling satisfy the Schrödinger equation, calculating the probability of tunneling and the relationship between the tunneling height and width, resulting in the conclusion that the minimum width of the Delta-doped barrier should be above 1 nm. From there, one can design the doping structure and doping concentration. The discussion covers that CMOS with Delta doping features high efficiency, stability, and uniform quantum efficiency, which enhances low-energy electron detection and contributes to low-light imaging and space exploration.