Question

In extrinsic semiconductors :

• A. the conduction band and valence band overlap
• B. the gap between conduction band and valence band is near about $16eV$
• C. the gap between conduction band and valence band is near about $1eV$
• D. the gap between conduction band and valence band will be $100eV$ and more
  

Answer 1

The correct option is C the gap between conduction band and valence band is near about $1eV$

In extrinsic semiconductors, formation of donor or acceptor level takes place in forbidden energy gap. Thus, some of the electrons in valance band acquire enough energy to jump to donor level or acceptor level present in forbidden energy gap. Thus, to obtain large number of electrons in conduction band some energy to be supplied to the electrons in valance band. For extrinsic semiconductors, it is nearly equal to $1eV$.