Question

Doping silicon with boron produces a:
A) n-type semiconductor
B) p-type semiconductor
C) metallic conductor
D) insulator

Answer 1

We know that boron is a chemical element which belongs to the third group of the periodic table. Boron contains three electrons in its valence shell. Thus, boron is a trivalent element.

Complete step by step answer: We know that the valence shell of boron has three electrons. And the valence shell of silicon has four electrons. These electrons are known as valence electrons.
When silicon is doped with boron, the three electrons of boron bond with the three electrons of silicon. The bond between the electrons is the covalent bond.
One valence electron of silicon remains free. To bond with this one free electron of silicon one electron from the neighbouring silicon atom is taken. This creates a hole or vacancy in the conductor.
Thus, a hole or vacancy is created. As a result, a p-type semiconductor is formed. ‘p’ in p-type semiconductor stands for positive.
In a p-type semiconductor, the number of holes is very large as compared to the number of electrons
Thus, the holes are the major charge carrier and the electrons are the minor charge carriers for the p-type semiconductor.
Thus, doping silicon with boron produces a p-type semiconductor.
Thus, the correct option is (B) p-type semiconductor.

Note: n-type semiconductors are formed when silicon is doped with a pentavalent element like arsenic, phosphorous, etc. On doping with pentavalent elements there remains one free electron. Thus, for n-type semiconductors, electrons are the major charge carriers and holes are the minor charge carriers. ‘n’ in n-type semiconductor stands for negative.