Intrinsic Silicon

1. Intrinsic silicon or crystal of pure contains a regular lattice structure. Whereas the atoms are held at their set positions by bonds, known as Covalent bonds, composed by four valence electrons connected with four each silicon atom.
2. At adequately low temperature these covalent bond are unbroken and not (very few) free electrons are available for conduct electric current.
3. Thermal ionization product in free electrons and holes in equivalent numbers and therefore equal concentrations. These holes & free electrons move arbitrarily through silicon crystal structure, and in this procedure some electrons can fill some holes. This procedure is  called upon RECOMBINATION
4. It consequence in disappearance of holes and free electrons. The recombination rate is proportional to the number of holes and free electrons, which in turn is finding out by ionization rate.