Physics and Engineering of Radiation Detection

5.1. Semiconductor Detectors 271

Table 5.1.4: Common donor and acceptor elements used to dope silicon. Also given
are their ionization energies (47).

Doping Agent Symbol Type Ionization Energy (eV)

Arsenic As Donor 0.054

Phosphorus P Donor 0.045

Antimony Sb Donor 0.043

Aluminum Al Acceptor 0.072

Boron B Acceptor 0.045

Gallium Ga Acceptor 0.074

Indium In Acceptor 0.157

and producing the related quantities for use in computations required for detector
development and operation (see Table 5.1.5).

Table 5.1.5: Mobilities (μe,μh,) velocities (ve,vh), and diffusion coefficients (De,Dh)
of electrons and holes in silicon (47).

Property Symbol Value

Electron Mobility μe ≤ 1400 cm^2 V−^1 s−^1

Hole Mobility μh ≤ 450 cm^2 V−^1 s−^1

Electron Thermal Velocity ve 2. 3 × 105 ms−^1

Hole Thermal Velocity vh 1. 65 × 105 ms−^1

Electron Diffusion Coefficient De ≤ 36 cm^2 s−^1

Hole Diffusion Coefficient Dh ≤ 12 cm^2 s−^1

The reader might be wondering as to why in Table 5.1.5 only the upper bounds
on the diffusion coefficient and mobility values have been given in Table 5.1.5. The
reason is that these parameters depend on various factors, such as temperature,
impurity type and concentration, and doping. This can be appreciated by looking
at figures 5.1.11 and 5.1.12, which are the plots of electron and ion mobilities versus
donor density. The plots have two interesting features. One is their non-linearity