Optimization of shielding electrode lengths of virtual Frisch-grid CdZnTe radiation detector for gamma-ray detection

Room-temperature semiconductor radiation detectors (RTSDs) such as cadmium zinc telluride (CZT) have been under development for several decades to provide a high performance for gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. However, the performance of CZT is limited in terms of the energy resolution by an incomplete charge collection owing to the slow mobility of the hole and polarization effects. To overcome such limitation, a virtual Frisch-grid CZT detector using a single polarity charge sensing method has been introduced. In this paper, we optimized the shielding electrode length of a virtual Frisch-grid to enhance the energy resolution and detection efficiency. In addition, the applied bias can be decreased by using the relatively thin (40 μm) encapsulate materials to reduce the system power consumption. The detector was fabricated using 5 × 5 × 14 mm3 CZT from Redlen, and the fabrication process used to make the virtual Frisch-grid CZT radiation detector is described. Characteristics such as the current-to-voltage curve, energy resolution, electron mobility life-time products, and intrinsic detection efficiency are compared by varying the shielding electrode lengths of the virtual Frisch-grid CZT detector. The results from these measurements will give us an optimal shielding electrode length and achieve a higher performance for a room-temperature radiation detector.