The impurity atoms with which pure silicon may be doped to make it a p-type semiconductor are those of
A. Phosphorous
B. Boron
C. Antimony
D. Aluminum
E. Graphite
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → B and D only
A p-type semiconductor is made by doping silicon (valency 4) with a trivalent impurity, whose atoms have one valence electron too few and so create holes.
A. Phosphorous — Incorrect. It is pentavalent (group 15), a donor that gives an n-type semiconductor.
B. Boron — Correct. It is trivalent, an acceptor impurity.
C. Antimony — Incorrect. It is pentavalent, a donor that gives an n-type semiconductor.
D. Aluminum — Correct. It is trivalent, an acceptor impurity.
E. Graphite — Incorrect. It is carbon, which is tetravalent like silicon, so it creates neither extra electrons nor holes.
NCERT (2026-27):
Extrinsic Semiconductor – “… There are two types of dopants used in doping the tetravalent Si or Ge: (i) Pentavalent (valency 5); like Arsenic (As), Antimony (Sb), Phosphorous (P), etc. … (ii) Trivalent (valency 3); like Indium (In), Boron (B), Aluminium (Al), etc. … Therefore, extrinsic semiconductors doped with trivalent impurity are called p-type semiconductors.”