Radiation Detection and Measurement

**67**

than 109

cm<sup>−</sup><sup>3</sup>

**Chapter 5**

**Abstract**

recently.

**1. Introduction**

High Purity Germanium: From

Gamma-Ray Detection to Dark

Matter Subterranean Detectors

*Nicolas Fourches, Magdalena Zielińska and Gabriel Charles*

High purity germanium remains the material of choice for the detection of photons in the range of MeV or higher, down to the hard X-ray range. Since the operation of HPGe-based detectors is possible only at or below the liquid nitrogen temperature, their advantage is mainly the resolution, which matches the Fano factor if appropriate cooled electronic readout is used. We focus here on present-day applications of HPGe detectors, which are now broader than ever despite the recent development of room-temperature photon detectors based on binary compounds. We present in particular dark matter detectors and γ-ray trackers as examples of the recent applications of HPGe as a detecting medium. More generally, we discuss the future of γ-ray detectors and the role that the semiconductor detectors will keep with respect to alternative detection materials. This chapter is an introduction to this general topic, and the reader is encouraged to refer to research and review articles on this subject published in the past or

**Keywords:** high purity germanium, traps and defects, gamma-ray detection,

This chapter provides a technical overview of HPGe detectors and their applications, both in science and day-to-day life. This overview covers the applications of HPGe as a material for γ-ray detection and its other more recent use in particle physics. It represents an introduction rather than a complete and exhaustive

Since the 1970s, photon detectors (γ and X) have been developed from high purity germanium [1]. The reason why HPGe has remained in use for such a long time as high-resolution γ- and X-ray detector material is mainly because it contains a very low concentration of electrically active defects [2, 3] which may be lower

for detector-grade silicon, the doping level is slightly higher. High electron density (Z = 32), together with low average energy, is needed for e-h pair generation. Above 1 keV of initial particle energy, germanium is a good choice for the detection of photon or ionizing particles. See **Table 1** and Refs. [4–10] for studies, both

. Such value is difficult to reach in compound semiconductors. Even

dark matter, nuclear spectroscopy, nuclear material monitoring

description of possible detector applications of HPGe.
