Numerical modeling of charge sharing in CdZnTe pixel detectors

In this paper, we describe charge collection in CdZnTe pixel detectors, with emphasis on events split between multiple pixels (charge-sharing events). We describe the design of the CdZnTe pixel sensors, being developed for the balloon-borne High-Energy Focusing Telescope (HEFT), and discuss investigations of charge sharing between pixels. We have developed a numerical model that emulates the physical processes of charge transport within the CdZnTe crystal. We discuss this numerical model in detail here. With this model, we are able to reproduce the general features of charge-sharing events. We have found that the amount of charge loss is very sensitive to the surface mutau (the product of charge mobility and trapping time), and we present estimates of (mutau)(surface) derived from our model. Further work will focus on more detailed analysis of diffusion in order to gain a complete understanding of these charge-sharing events in CdZnTe pixel detectors.