Question

When a hole is produced in P-type semiconductor, there is
A. Extra electron in valence band
B. Extra electron in conduction band
C. Missing electron in valence band
D. Missing electron in conduction band

Answer 1

Hint: Firstly, we could understand what actually a hole physically is. You may also recall what these p-type semiconductors are by giving a brief description of its formation. Also, remember that these holes are known to be positive charge carriers, so you could be sure that they aren’t extra electrons.

Complete solution:
In the question, we are asked to find the implication of production of a hole in p-type semiconductor.
You may recall that the holes have positive charge and electrons are known to have negative charge. A hole is never produced by itself but is the indication of absence of electrons in the valence band. So, we could say that production of holes means there is a missing electron in the valence band.

Hence, option C is found to be the correct answer.

Additional information:
Now have a brief discussion on p-type semiconductors. They are formed by doping trivalent impurities like Boron, Aluminium, etc to silicon and Germanium. We know that silicon and germanium has a valency of 4. So, the addition of trivalent impurities may cause a deficiency of an electron in the valence shell of each atom. Hence, these p-type semiconductors have holes as majority carriers.
The neighboring electron moves to this hole and produces a hole in its initial position. Though the movement is actually that of the electron, it appears as if the hole has moved.

Note:
Another type of semiconductors are the n-type semiconductors. They are formed as the result of doping pentavalent impurities into silicon and Germanium. As a result of this doping process, an excess of electrons occurs in them and thus we could say that electrons are the majority charge carriers in n-type semiconductors.