Study on the spectrum improvement of a capacitive Frisch grid structure for CdZnTe Detector

Abstract

The design and fabrication of a capacitive Frisch grid structure for CdZnTe (CZT) detector have been investigated in this paper. The simulation results show that a bigger ratio of L/H (metal screen ring length/device height) with the ratio of ɛr/d at 20 mm−1 (relative dielectric constant/the thickness of insulation layer) helps to compress the weighting potential towards the anode, and therefore to improve the energy resolution as showed by the experimental results. The capacitive Frisch grid structures significantly improve spectroscopic performance of planar CZT detectors. In particular, a passivation layer obtained by two-step passivation processing, combined with a Teflon tape was used for an insulated layer of the capacitive Frisch grid detector which can be applied at high voltage. A typical FWHM energy resolution of 4.58% at 662 keV was obtained for a device with dimensions of 5 × 5 × 10 mm3.