Question

Doping a semiconductor with a trivalent impurity results in:

• A. p-type semiconductor
• B. n-type semiconductor
• C. intrinsic semiconductor
• D. perfect insulator

Hint:

Group 13 → p-type Group 15 → n-type

Answer 1

The Correct Option is A

Step 1: Understand doping.
Doping means adding a small amount of another element into a pure semiconductor like silicon or germanium to change how it conducts.

Step 2: Look at a trivalent impurity.
A trivalent atom, such as boron or aluminium, has only three valence electrons available for bonding.

Step 3: Compare with silicon's bonds.
Silicon needs four electrons to form four covalent bonds with its neighbours. The trivalent atom can only fill three of them.

Step 4: See what is missing.
One bond is left short of an electron. That empty spot behaves like a positive charge carrier called a hole.

Step 5: Identify the carrier type.
Because the main charge carriers are positive holes, the material is called a p-type semiconductor.

Step 6: State the answer.
Doping with a trivalent impurity makes a p-type semiconductor. \[ \boxed{\text{p-type semiconductor}} \]