question_answer

Distinguish between intrinsic and extrinsic semiconductors on the basis of energy-band diagram.                                            Or                     Distinguish between n-type and p-type semi- conductors on the basis of energy band diagram.                                       

Answer:

                    In intrinsic semiconductors, there are only few free electrons in conduction band and an equal number of holes in valence band [Fig. (a)] In n-type extrinsic semiconductors, the number of free electrons in conduction band is much more than the number of holes in valence band. The donor energy level lies just below the conduction band [Fig. (b)]. In p-type extrinsic semiconductors, the number of holes in valence band is much more than the number of free electrons in conduction band. The acceptor energy level lies just above the valence band [Fig. (c)].