Question

For a p-type semiconductor, which of the following statements is true?
A. Electrons are the majority carriers and trivalent atoms are the dopants.
B. Holes are the majority carriers and trivalent atoms are the dopants.
C. Holes are the majority carriers and pentavalent atoms are the dopants.
D. Electrons are the majority carriers and pentavalent atoms are the dopants.

Answer 1

Hint: The p-type semiconductor has majority positive charge dominating over the negative charge. An intrinsic semiconductor can be converted into a p-type semiconductor by adding a dopant which is a lesser number of valence electrons than the atom from which the semiconductor is made.

Complete step by step answer:
An intrinsic semiconductor is characterized by the fact that it contains equal concentration of negatively charged electrons and positively charged holes. These semiconductors are mostly made of silicon or germanium which are tetravalent atoms.
We can dope an intrinsic semiconductor in two ways: We can either add a trivalent atom to it or we can add a pentavalent atom to it.
When we add a trivalent atom to the intrinsic semiconductor, then one positively charged vacancy is created due to every dopant atom added to the lattice of the intrinsic semiconductor, which is known as hole. These holes act as the majority charge carriers and since holes are positively charged, this type of semiconductor is known as p-type semiconductor.

So, the correct answer is “Option B”.

Note:
1. It should be noted that if we use a pentavalent atom as a dopant for an intrinsic semiconductor then we will obtain one extra electron from each dopant atom and the electrons will be the majority charge carriers and such type of semiconductor is known as n-type semiconductor.
2. If we add a tetravalent atom to the intrinsic semiconductor then we do not get any majority of charge carriers as they create neither a vacancy or an excess electron in the lattice of the semiconductor, so the number of holes remain the same as the number of electrons in this case.