Simulation of Coplanar Proximity Charge Sensing Electrodes in CZT Detectors

The concept of applying proximity charge sensing electrodes to semiconductor radiation detectors is a novel technique that has distinct advantages over directly deposited electrodes. This paper evaluates the application of proximity charge sensing onto a CdZnTe (CZT) semiconductor crystal using ANSYS Maxwell simulation software to calculate the weighting potential across the detector depth, the weighting potential across the detector width, and the electric field (E) generated inside the detector volume for multiple designs. To accomplish this goal, several variables are studied in the simulated designs: (1) a high resistivity thin-film material that is applied to the detector proximity surface from the anode side, (2) an appropriate metal that acts as an Ohmic contact to dissipate generated charges on the CZT anode side, and finally (3) an insulating layer (dielectric) to isolate the CZT detector body from the proximity electrodes. The results of the generated weighting potentials for both directly deposited electrodes and proximity-sensing electrodes, having the same electrode width and pitch, have been quantitatively compared using a figure of merit (FOM). The FOM compares the weighting potential created by each simulated design for weighting potential uniformity and weighting potential similarity.