ABSTRACT
Metals, semiconductors and insulators are classified by their electrical resistivity. The band gap indicates the energy difference between conduction band and valence band. Band theory of solids explains the behavior of metals, semiconductors and insulators. Extrinsic semiconductors of n and p type have been explained. The temperature dependence for a semiconducting material has been shown by figure. Interpretation of semiconductors has also been given by free electron theory. Brillouin zone has been explained and a mathematical interpretation of band theory has been dealt with.
