Question: Q. 2. (i) Draw the energy band diagrams of (a) $n$-type (b) $p$-type semiconductor at temperature, $T>0 K$.
(ii) In the case $n$-type semiconductor, the donor energy level is slightly below the bottom of conduction band whereas in $p$-type semiconductor, the acceptor energy level is slightly above the top of the valence band. Explain what role these energy levels play in conduction and valence bands.
U [OD I, II, III 2015]
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Solution:
Ans. (i) Try yourself, Similar to Q. 2 Short Answer Type-I.
(ii) In case of $n$-type semiconductor, electrons from donor impurity atoms will move into conduction band with very small supply of energy. Hence, the conduction band will therefore have electrons as majority charge carriers.
In case of $p$-type semiconductor, very small supply of energy can cause an electron from its valence band to jump to the acceptor energy level. Hence, the valence band will have dominant density of holes which shows that holes are the majority charge carriers in $p$-type semiconductor.
