Question

Consider the following statements: A. The intrinsic concentration of carriers is independent of temperature B. Current due to carrier drift occurs in both semiconductor and metals C. Current due to carrier diffusion exists in both semiconductor and metals D. Metals are unipolar while semiconductors have bipolar nature

• A. A and B only
• B. B and D only
• C. A, C and D only
• D. A and D only

Hint:

Semiconductors → both drift and diffusion; Metals → mostly drift.

Answer 1

The Correct Option is B

Concept: Carrier transport in materials depends on drift and diffusion mechanisms.

Step 1: Statement A Intrinsic carrier concentration depends strongly on temperature: \[ n_i \propto e^{-E_g/2kT} \] \[ \Rightarrow \text{A is FALSE} \]

Step 2: Statement B Drift current occurs in both metals and semiconductors. \[ \Rightarrow \text{B is TRUE} \]

Step 3: Statement C Diffusion current is significant mainly in semiconductors, not metals. \[ \Rightarrow \text{C is FALSE} \]

Step 4: Statement D Metals → single carrier (electrons) → unipolar Semiconductors → electrons + holes → bipolar \[ \Rightarrow \text{D is TRUE} \] \[ \therefore \text{Correct answer is (B)} \]