Doping

  Doping is the process of introducing impurities (atoms with Z different from the basic element) into scintillating materials ( Scintillation Counter) or semiconductors ( Semiconductor Detectors), in order to improve their detection properties.

In semiconductors, doping typically produces a region with different charge carrier concentration, or modifies other properties of the bulk. Electrically active dopants belong to groups III and V of the Mendeleev table. For Si, they are usually boron and phosphorus (or arsenic), to produce p- and n-type material. Typical concentrations of dopants in detector grade silicon are in the range of 10¹² atoms/cm³ [Dreier90].

Other dopants (e.g. metals, increased carbon or oxygen concentrations) are used for special purposes, to modify the probability of recombination of different defects and the defects kinetics, in defect engineering.

Bulk doping is the result of the growth process of the monocrystalline material, and depends on technology and initial material. Highly doped shallow regions, e.g. the abrupt p-n junction in a semiconductor diode detector, are produced by ion implantation, diffusion or a combination of both techniques.

A basic reference to semiconductor devices is [Sze81]; a good introductory text is [Klanner85].