Analytical charge collection and MTF model for photodiode-based CMOS imagers

An analytical charge collection model is derived to assess the impact of the photodiode size, doping profile and surface recombination velocity on the modulation transfer function (MTF) and the charge collection efficiency of CMOS imagers. The effects of the microlens and optical isolation are also quantitatively analyzed. The calculated MTF results agree well with measured data of fabricated imagers based on three different pixel designs.