Charge transfer in a multi-implant pinned-buried photodetector

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.