The best way to understand a semiconductor is to consider the band
structure of the material.
The conduction and
valence bands are separated by a
forbidden gap called the 'band
size of which determines whether the material is classified as:
The interaction of a gamma-ray with semiconductor material can
produce primary electrons with energies considerably larger than
thermal energies. These interactions can raise electrons from deep
occupied bands into energy levels well above the base of the
conduction band. The resulting deeply embedded holes and the excited
electrons will tend to redistribute themselves among the available
energy levels until:
- the electrons lie at the bottom of the conduction band;
- the holes lie at the top of the valence band.
The simulation illustrates the three types of material and the direction
of travel of electrons and holes in these materials.
It is important to understand that the mobility of electrons and
holes both contribute to conductivity, for further explanation see here...