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Nuclear Safeguards Education Portal
  

Introduction

Diagram of a semiconductor detector.
Diagram of a semiconductor detector.  

Semiconductor detectors are solid-state devices that operate essentially like ionization chambers. The charge carriers in semiconductors are not electrons and ions, as in gas counters, but electrons and holes. Radiation incident upon the semiconducting junction produces electron-hole pairs as it passes through it. Electrons and holes are swept away under the influence of the electric field, and the proper electronics can collect the charge in a pulse. The sensitive volume of a semiconductor detector, which is also known as the depleted region, is an electronically conditioned region in the semiconductor material in which liberated electrons and holes move freely.

What Is a Semiconductor?

A semiconductor is a solid material that has electrical conductivity between a conductor and an insulator. Insulators have larger band gaps (energies that electrons must acquire to be free to move from atom to atom). When a semiconductor is at room temperature, very few electrons gain enough thermal energy to leap the band gap, which is necessary for electrons to be available for electric current conduction. The smaller bandgaps of semiconductors, however, allow for other means besides temperature to control their electrical properties

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Examples of some Semiconductor Detectors are:

  • High-Purity Germanium (HPGe) detectors
  • Germanium Lithium-drifted (GeLi) detectors
  • Silicon Lithium-drifted (SiLi) detectors
  • Cadmium Telluride (CdTe) detectors
  • Cadmium Zinc Telluride (CdZnTe) detectors
  • Mercury Iodide (HgI2) detectors

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