What is an intrinsic semiconductor? How can this material be converted into (i) P-type (ii) N-type extrinsic semiconductor? Explain with the help of energy band diagram ?

Semiconductors that are chemically pure, in other words, free from impurities are termed as intrinsic semiconductors. The number of holes and electrons is therfore determined by the properties of the material itself instead of the impurities. In instrinsic semiconductors, the number of excited electrons is equal to the number of holes;n=p. They are also termed as undoped semiconductors or i-type semiconductors. Silicon and germanium are examples of i-type semiconductors. These elements belong to the IVth Group of the periodic table and their atomic numbers are 14 and 32 respectively.