Question

When a PN junction diode is forward biased, the CORRECT statement is

• A. the majority carrier current is zero
• B. the junction resistance is large
• C. the width of depletion layer is reduced
• D. the width of depletion layer is increased
• E. the minority carrier current is large

Hint:

Forward bias = Narrow depletion layer = Low resistance = High current.
Reverse bias = Wide depletion layer = High resistance = Low current.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Forward biasing a PN junction means connecting the positive terminal of the battery to the P-type semiconductor and the negative terminal to the N-type. This external field pushes charge carriers toward the junction.
Step 2: Key Formula or Approach:
Recall theoretical semiconductor principles:
The external voltage opposes the built-in potential barrier.
This results in a narrowing of the physical zone where no mobile charge carriers exist (the depletion region).
Step 3: Detailed Explanation:
Let's analyze the options based on forward bias conditions:
(A) The majority carrier current is zero: False. Forward bias heavily promotes majority carrier flow across the junction.
(B) The junction resistance is large: False. Forward bias drastically reduces resistance, allowing easy current flow.
(C) The width of the depletion layer is reduced: True. The applied potential pushes holes from P and electrons from N into the depletion region, physically narrowing it and lowering the potential barrier.
(D) The width of depletion layer is increased: False. This happens during reverse bias.
(E) The minority carrier current is large: False. Reverse current is dominated by minority carriers; forward current is dominated by majority carriers.
Step 4: Final Answer:
The width of depletion layer is reduced.