The Significance of High-Level Carrier Generation Conditions for Charge Collection in Irradiated Devices

Pulsed-laser induced charge-collection measurements in a bulk silicon diode are used to investigate charge collection mechanisms during high-level carrier generation conditions. The recently developed Ambipolar Diffusion with a Cutoff (ADC) model for charge collection is used to emphasize the significance of the carrier densities, electric fields, and potential throughout the entire device in response to high-level carrier generation events. Device-level simulations are used to show that for high carrier density, short-track events, carriers are confined close to the junction by a strong electric field that forms underneath the region of high carrier density. These simulations are used to explain why, for some of the experimental data shown here, almost all of the generated charge can be collected, even if the peak carrier generation is located several micrometers away from the depletion region boundary. The physical framework for charge collection provided by the ADC model is compared to other analytical charge collection models, such as the funnel model, to emphasize that the more general approach it provides makes it well suited to situations where other analytical charge-collection models cannot be directly applied.