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An intrinsic semiconductor is a pure semiconductor, i.e., a sample without any impurity. At absolute zero it is essentially an insulator, though with a much smaller band gap. However, at any finite temperature there are some charge carriers are thermally excited, contributing to conductivity. Semiconductors such as silicon and germanium, which belong to Group IV of the periodic table are covalently bonded with each atom of Si(or Ge) sharing an electron with four neighbours of the same specis. A bond picture of silicon is shown in the figure where a silicon atom and its neighbour share a pair of electrons in covalent bonding. |
