In complementary metal-oxide-semiconductor (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. It was assumed that the total energy of electrons and the cross-sectional direction of tunneling satisfied the Schrodinger equation, calculating the probability of tunneling and the relationship between the tunneling height and width, and resulting in the conclusion that the minimum width of the Delta-doped barrier should be above 1 nm, thereby designing the doping structure and doping concentration. It was discussed that CMOS with Delta doping had the feature of high-efficient, stable, and uniform quantum efficiency, which enhanced low-energy electron detection and contributed to low-light imaging and space exploration.