question_answer

In semiconductors at a room temperature

A)  the valence band is partially empty and the conduction band is partially filled

B)  the valence band is completely filled and the conduction band is partially filled

C)  the valence band is completely filled

D)  the conduction band is completely empty

Correct Answer: A

Solution :

The energy band scheme of semiconductors is shown here. All the gates in the combination are NAND gates. In semiconductors, valence band and conduction band are separated by an energy gap called the forbidden energy gap. It is very small. At room temperature some electrons in valence band acquire thermal energy. This energy is more than forbidden energy gap\[{{E}_{g}}\], thus they jump into the conduction band and leaves their vacancy in the valence band which act as holes. Hence, at room temperature valence band is partially empty and conduction band is partially filled.