Intrinsic semiconductors

Intrinsic semiconductors are pure, stoichiometric materials that have not been doped with additional compounds in order to modify their electrical conductivity. The band gap of these materials increases as we move from group IV materials like silicon and germanium to III-V (GaAs etc) and II-VI (ZnTe etc). We can see how each electron in the conduction band comes from creating a hole in the valence band. Both species become mobile in response to an applied electric field. We can calculate the overall electrical conductivity by considering the number of intrinsic carriers and multiplying this by the charge of an electron and the mobility of each species.