This work presents a charge transfer model for a multi-implant (graded) pin
ned-buried photodetector for high frame rate imaging applications. The mode
l takes into account the initial charge of each implanted region which is d
ivided into a large number of small areas and the maximum effective transit
length of the far and near electrons by taking into account the fringing f
ield effect due to graded implants under uniform illumination condition. Th
e model predicts 1.5 mus for a single-implant and 500 ns for a three-implan
t photodetector for collection of 90% of the initial charge. The computed v
alues agree well with the experimental results for a three-implant 70 mum x
45 mum photodetector measured at a rate of 10(6) frames/s with uniformly i
lluminated by 100 ns LED pulses.