Project

Charge transfer model for three N-type implant pinned-buried photodetector under uniform illumination condition was developed. According to this model the photodetector is divided into large number of small areas, and under the uniform illumination condition the initial charge on each small area is directly proportional to its area. Each small area is associated with a maximum effective diffusion length (after taking into account the fringing field drift). The diffusion equation and continuity equation give charge decaying equation for the small area. The total charge as a function of time is obtained by the superposition of charges of all small areas at time t. The total charge as a function of time for different electron mobility was obtained and compared with the experimental results of the Princeton Scientific Instrument PSI-2 Pixel Photodetector. The results obtained by this model for electron mobility of 700 cm2/V.sec, 600 cm2/V.sec, and 500 cm2/V.sec for first, second, and third implant regions respectively match with the experimental values.