Semiconductor detectors

Semiconductor Ge and Si detectors have served the scientific community for many years. Recent advances as well as emerging new applications demand a deeper understanding of gamma ray spectrometry. Besides Ge and Si, the CdZnTe («CZT») semiconductor detectors are being increasingly used in many applications. Some general properties of Ge, Si, and CZT are reviewed. A second section is devoted to Ge detectors. The complexity of a gamma ray spectrum, the influence of factors such as energy resolution and efficiency, background radiation, and the minimum detectable activity (MDA) are discussed. The third section is devoted to Si detectors: Si(Li) detectors are similar to Ge detectors in many aspects. The modern version of charged particle detectors are the passivated implanted planar silicon (PIPS) detectors. Special types find application in continuous air monitoring and high-energy physics applications. Efficiency, resolution, and stability, as well as background issues and the resulting MDA, are discussed. The silicon drift detector (SDD) technology, which is ideal for low-energy X-ray spectroscopy and electron spectroscopy, is also discussed in the third section of the chapter. The fourth section of the chapter describes the characteristics of CZT detectors. Crystal growth techniques are described. Limitations due to poor hole mobility and techniques to mitigate these limitations are described. The fifth section of the chapter goes into the details of spectroscopic analysis with semiconductor detectors. Sample preparation is explained in great detail. The sixth and seventh sections of this chapter are devoted to discussing the advances made in Ge detector technology that have enabled their use in gamma ray imaging and nuclear physics applications. Segmented Ge detectors are discussed. Experiments conducted by Majorana and GERDA international research collaborations to search for neutrinoless double beta decay are described.