Charge transfer in a multi-implant pinned-buried photodetector

This work presents a charge transfer model for a multi-implant (graded) pinned-buried photodetector for high frame rate imaging applications. The model takes into account the initial charge of each implanted region which is divided 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 field effect due to graded implants under uniform illumination condition. The model predicts 1.5 μs for a single-implant and 500 ns for a three-implant photodetector for collection of 90% of the initial charge. The computed values agree well with the experimental results for a three-implant 70 μm×45 μm photodetector measured at a rate of 10⁶ frames/s with uniform illumination by 100 ns LED pulses