Question: Q. 1. (i) Distinguish between $n$-type and $p$-type semiconductors on the basis of energy band diagrams.
(ii) Compare their conductivities at absolute zero temperature and at room temperature.
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Solution:
Ans. (i)
R [Delhi1, II, III 2015]
| $n$-type semiconductor | $p$-type semiconductor |
|---|---|
| In this, an extra energy level known as donor energy level is produced below the bottom of the conduction band. |
In this, extra energy band known as acceptor energy level is produced above the top of valence band. |
| In this, most of the electrons come from the donor impurity. |
In this, density of holes in valence band is predominantly due to impurity in extrinsic semiconductors. |
 |
 |
| $n_{e}>n_{h}$ | $n_{h}>n_{e}$ |
[Any one of the above, or any one, other correct distinguishing feature]
(ii) At absolute zero temperature conductivities of both type of semiconductors will be zero.
1 For equal doping, an $n$-type semi conductor will have more conductivity than a $p$-type semiconductor, at room temperature.
$$ 1 $$
