Non-uniformity effects in CdZnTe coplanar-grid detectors

We discuss the findings from our studies of the performance of commercial coplanar-grid CdZnTe detectors. The devices were investigated using a highly collimated X-ray beam available at Brookhaven's National Synchrotron Light Source, and by applying pulse-shape analysis to measure correlations between the signals read out from the devices. Although the operational principle of coplanar-grid (CPG) detectors is well known, we found some important new details that help to better clarify the performance limitations of this type of device. The correlation plots we present can also be used as diagnostic tools to characterize the behavior of the CPG devices and to help to improve the designs of electrodes. This work illustrates the typical limitations related to the geometry of the contacts in CPG devices and how material nonuniformities can amplify these problems.