Question

When the conductivity of a semiconductor is only due to the breaking of the covalent bonds, the semiconductor is called}

• A. donor
• B. intrinsic
• C. acceptor
• D. extrinsic

Hint:

Intrinsic means 'pure'; extrinsic means 'doped' with impurities (donors or acceptors).

Answer 1

The Correct Option is C

Concept:
Semiconductors are classified as:

• Intrinsic semiconductor: Pure semiconductor without impurity
• Extrinsic semiconductor: Semiconductor doped with impurity

Impurities added are of two types:

• Donor impurity $\Rightarrow$ gives n-type semiconductor
• Acceptor impurity $\Rightarrow$ gives p-type semiconductor

Step 1: Meaning of acceptor impurity
An acceptor impurity is a trivalent atom such as: \[ B,\ Al,\ Ga,\ In \] These atoms have only three valence electrons. When added to silicon or germanium, they accept an electron from neighboring atoms and create a hole.
Step 2: Type of semiconductor formed
Because holes are created as majority charge carriers: \[ \text{p-type semiconductor is formed} \] Thus, impurity responsible for creating holes is called acceptor impurity.
Step 3: Why other options are incorrect

• Donor impurity gives extra electrons.
• Intrinsic means pure semiconductor.
• Acceptor specifically creates holes.

Step 4: Final Answer
The correct answer is: \[ \boxed{\text{(C) Acceptor \] Quick Tip:
Trivalent impurity accepts electron $\Rightarrow$ creates hole $\Rightarrow$ p-type semiconductor.