CZT virtual Frisch-grid detector: Principles and applications

Abstract

Abstract-Cadmium Zinc Telluride (CdZnTe or CZT) is a very attractive material for using as room-temperature semiconductor detectors, because it has a wide bandgap and a high atomic number. However, due to the material's poor hole mobility, several special techniques were developed to ensure its suitability for radiation detection. Among them, the virtual Frisch-grid CZT detector is an attractive option, having a simple configuration, yet delivering an outstanding spectral performance. The goal of our group in Brookhaven National Laboratory (BNL) is to improve the performance of Frisch-ring CZT detectors; most recently, that effort focused on the non-contacting Frisch-ring detector, allowing us to build an inexpensive, large-volume detector array with high energy-resolution and a large effective area. In this paper, the principles of virtual Frisch-grid detectors are described, especially BNL's innovative improvements. The potential applications of virtual Frisch-grid detectors are discussed, and as an example, a hand-held gamma-ray spectrometer using a CZT virtual Frischgrid detector array is introduced, which is a self-contained device with a radiation detector, readout circuit, communication circuit, and high-voltage supply. It has good energy resolution of 1.4% (FWHM of 662-keV peak) with a total detection volume of ~20 cm 3 . Such a portable inexpensive device can be used widely in nonproliferation applications, non-destructive detection, radiation imaging, and for homeland security. Extended systems based on the same technology have potential applications in industrial-and nuclear-medical-imaging.

Characterization of a CdZnTe detector for a low-power CubeSat application

“…At the same time, the wider band gap and low leakage currents are favourable for low noise measurement and promise an excellent energy resolution performance at room temperature. In the current state of technology CdZnTe detectors can be produced with high quality up to few cm 3 in volume. Therefore CdZnTe detectors are well suited for the development of compact and reliable radiation detection systems, and appealing for a large variety of applications, from nuclear medicine and radiation monitoring, to X-ray and gamma-ray astronomy.…”

“…In order to operate the detectors with optimal performance, special electrode configurations which rely on the electron charge collection and are insensitive to the hole contribution, need to be implemented. Such configurations, also referred to as single charge carrier devices, include the virtual Frisch grid [3], small pixel arrays or strips [4], the co-planar grid [5,6] and orthogonal strips [7] geometries. A complete review of these configurations and principle of operation can be found, for example, in Ref.…”

Characterization of a CdZnTe detector for a low-power CubeSat application

“…In order to operate the detectors with optimal performance, special electrode configurations which rely on the electron charge collection and are insensitive to the hole contribution, need to be implemented. Such configurations, also referred to as single charge carrier devices, include the virtual Frisch grid [3], small pixel arrays or strips [4], the co-planar grid [5,6] and orthogonal strips [7] geometries. A complete review of these configurations and principle of operation can be found, for example, in [8] or [9].…”

Influence of Ring Length on Electric Field Distribution in CdZnTe Frisch-Ring Detector

“…Compared with planar CZT device, single-charge-carrier device designs alleviate many of the problems caused by hole trapping, among the recent single-charge-carrier devices, CZT Frisch-ring detector with its simple configuration and outstanding spectral performance attracts many attention [3,4] . The virtual CZT Frisch-ring detector is inexpensive, easy to fabricate, and readily integrated into large-area array [5] .…”