Numerical modelling of charge-sharing in CdZnTe pixel detectors

In this paper, we describe our study of charge-sharing events in CdZnTe detectors being developed for the HEFT telescope. We specify the detector design, and discuss an experiment we have performed to investigate charge sharing between pixels. We have also developed a numerical model to study the charge transport in the detector. It emulates the physical processes of charge transport within the CdZnTe crystal, especially the process of drift. We discuss this numerical model of the detector in detail. With our numerical model, we are able to reproduce the general features of the charge-sharing events. We have found that the amount of charge loss is very sensitive to the surface μτ, the product of charge mobility and trapping time, of CdZnTe; we present estimates of (μτ)_surface 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