From the following, choose the element for impurity atoms with which pure silicon should be doped to make it a p-type semiconductor:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Boron
A p-type semiconductor is made by doping silicon (valency 4) with a trivalent impurity. Each impurity atom has only three valence electrons to bond with four silicon neighbours, so one bond is left with a hole; the impurity is called an acceptor.
Boron is in group 13 and is trivalent, so it gives p-type silicon.
Arsenic, phosphorus and antimony are in group 15 and are pentavalent. They give an extra electron (donors) and make n-type silicon.
NCERT (2026-27):
p-type Semiconductor – “This is obtained when Si or Ge is doped with a trivalent impurity like Al, B, In, etc. The dopant has one valence electron less than Si or Ge and, therefore, this atom can form covalent bonds with neighbouring three Si atoms but does not have any electron to offer to the fourth Si atom.”