What is the Direction of Particle Motion in a p–n Junction?
📘 Question:
What is the direction of the particle motion that makes up the diffusion current in an isolated p–n junction?
- A) Both electrons and holes diffuse from the n material to the p material.
- B) Electrons diffuse from the n material to the p material, and holes diffuse in the opposite direction. ✅
- C) Electrons diffuse from the p material to the n material, and holes diffuse in the opposite direction.
- D) Both electrons and holes diffuse from the p material to the n material.
✅ Correct Answer: Electrons diffuse from the n material to the p material, and holes diffuse in the opposite direction.
🔍 Explanation:
In a p–n junction, the majority carriers are:
- 🟦 Electrons in the n-type region
- 🟥 Holes in the p-type region
🔁 Diffusion Process:
- 🟦 Electrons move from n ➝ p side
- 🟥 Holes move from p ➝ n side
This movement of carriers constitutes the diffusion current in the junction.
⚡ Depletion Region Formation:
When electrons and holes recombine at the junction:
- Immobile ions are left behind
- This forms a depletion zone
- An internal electric field is established to counteract further diffusion
✅ Summary: Electrons diffuse from the n side to the p side, while holes diffuse in the opposite direction, leading to the formation of a depletion region and an internal electric field.