Question

When a forward bias is applied to a p-n junction diode, then (A) majority carrier current becomes zero. (B) potential barrier is raised. (C) width of the depletion layer reduces. (D) junction resistance increases. Choose the correct answer from the options given below:

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

Hint:

For a forward-biased p-n junction: \[ \text{Barrier Potential} \downarrow \] \[ \text{Depletion Width} \downarrow \] \[ \text{Junction Resistance} \downarrow \] \[ \text{Current} \uparrow \] Remember: Forward bias assists the flow of majority carriers.

Answer 1

The Correct Option is B

Concept: In forward bias:
• The positive terminal is connected to the p-side.
• The negative terminal is connected to the n-side.
• The potential barrier decreases.
• The depletion region narrows.
• Junction resistance decreases.
• Majority carriers easily cross the junction.

Step 1:Check statement (A). Majority carriers are responsible for the forward current. Hence, majority carrier current does not become zero. \[ {\text{Statement (A) is false.}} \]

Step 2: Check statement (B). Forward bias lowers the barrier potential. \[ {\text{Statement (B) is false.}} \]

Step 3: Check statement (C). As the barrier potential decreases, the depletion region becomes thinner. \[ {\text{Statement (C) is true.}} \]

Step 4: Check statement (D). Forward bias increases current flow and therefore decreases junction resistance. \[ {\text{Statement (D) is false.}} \]

Step 5: State the answer. Only statement (C) is correct. \[ { \text{Width of the depletion layer reduces.} } \] Hence, the correct option is \[ {(B)} \]