Electronic Devices And Circuit Theory

the discovery of semiconductors have ushered in a new era of technology.the smart phones, the led`s that we see around us today are simply an application of this wonderful device..so what is a semiconductor??a semiconductor can be thought of as a material which possesses properties in between that of a conductor and an insulator.every material has an energy band.free electrons in the material are let`s say trapped in the valence band and in order for them to conduct electricity, they need to jump to the conduction band.so, as you see there are two bands in a material: 1. conduction band 2. valence band the energy gap in between these two bands is extremely large in case of insulators and this being the prime reason why the free electrons present in the insulators can`t conduct very easily, please note the use of the term very easily, meaning to say that insulators can also conduct but only when extremely high amount of energy is provided to them, in case of semiconductors the energy gap is very less of the order of 2MeV so a little amount of energy is required.semiconductors are of two types extrinsic semiconductors and intrinsic semiconductors.the extrinsic semiconductors are doped with impurities whereas intrinsic semiconductors are not.the extrinsic semiconductors are furthur classified into n type and p type semiconductors.the n type semiconductors are doped with impurities that provide an extra electron thus imparting a negative charge to the semiconductor material and the p type are doped with impurities that provide positive charge to the material i.e. p for positive.the element Si and Ge are the most popular semiconductors available.