Question

Which of the following statements is correct during the formation of a PN junction?

• A. Electrons diffuse from the P-region to the N-region.
• B. Holes diffuse from the N-region to the P-region.
• C. Electrons diffuse from the N-region to the P-region.
• D. Holes drift from the N-region to the P-region.

Hint:

Always remember the direction of diffusion in a PN junction: \[ \boxed{ \begin{aligned} \text{Electrons} &:\; N \rightarrow P,\\ \text{Holes} &:\; P \rightarrow N. \end{aligned} } \] The diffusion of charge carriers forms the depletion layer and the built-in potential barrier.

Answer 1

The Correct Option is C

Concept: A PN junction is formed by joining a P-type semiconductor with an N-type semiconductor. Due to the difference in carrier concentration, majority charge carriers diffuse across the junction.

• Electrons are the majority carriers in the N-region.

• Holes are the majority carriers in the P-region.
As soon as the junction is formed,

• Electrons diffuse from the N-region to the P-region.

• Holes diffuse from the P-region to the N-region.
This diffusion creates a depletion region and establishes a built-in electric field which opposes further diffusion.

Step 1: Identify the majority carriers.
In a P-type semiconductor, \[ \boxed{\text{Majority carriers = Holes}} \] In an N-type semiconductor, \[ \boxed{\text{Majority carriers = Electrons}} \]

Step 2: Understand the diffusion process.
Since the concentration of electrons is much higher in the N-region, \[ \boxed{\text{Electrons diffuse from N-region to P-region}.} \] Similarly, \[ \boxed{\text{Holes diffuse from P-region to N-region}.} \] This diffusion continues until equilibrium is established.

Step 3: Examine the given options.
Option (A): Electrons diffuse from P-region to N-region This is incorrect because electrons are majority carriers in the N-region. Option (B): Holes diffuse from N-region to P-region This is incorrect because holes are majority carriers in the P-region. Option (C): Electrons diffuse from N-region to P-region This is correct. Option (D): Holes drift from N-region to P-region This is incorrect because initially holes diffuse, not drift. Hence, \[ \boxed{\textbf{Option (C)}} \] is the correct answer.