Class 12 Physics Semiconductor Electronics Classification on the basis of energy bands

Classification on the basis of energy bands

  • Depending upon the relative position of the valence band and the conduction band, the solids can be classified into conductors, insulators and semiconductors

Conductors

  • The conduction band and the valence band partly overlop each other and there is no forbidden energy band gap in between
  • The electrons from the valence band can easily move into the conduction band
  • Hence, large number of electrons are available for conduction
  • The resistance of such materials is low and conductivity is high

Insulators

  • In case of insulators, a large energy gap exists between the valence band and the conduction band
  • The energy gap is so high that the electrons from the valence band cannot move to the conduction band by thermal excitation
  • As there is no electrons in the conduction band, electrical conduction is not possible

Semiconductors

  • A finite but a small energy gap exists between the valence band and the conduction band
  • At room temperature, some of the electrons from the valence band acquire energy and move into the conduction band
  • Hence, at high temperature, semiconductors have conductivity and resistance is also not as high as insulators

Types of semiconductors

  • There are two types – Intrinsic semiconductor and Extrinsic semiconductor

 

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