Question
Why does a PN-junction diode not conduct current when reverse biased?
Answer Options
- A) Only P-type semiconductor material can conduct current
- B) Only N-type semiconductor material can conduct current
- C) Holes in P-type material and electrons in the N-type material are separated by the applied voltage, widening the depletion region
- D) Excess holes in P-type material combine with the electrons in N-type material, converting the entire diode into an insulator
Correct Answer: C
Explanation
A PN-junction is the boundary between P-type and N-type semiconductor materials and is the fundamental structure of a diode. When a diode is reverse biased, an external DC voltage is applied with the positive terminal connected to the N-type side and the negative terminal to the P-type side.
This applied voltage attracts the free electrons (majority carriers in the N-type material) toward the positive terminal and attracts the holes (majority carriers in the P-type material) toward the negative terminal. This action pulls the majority carriers away from the junction, causing the non-conductive depletion region to widen, effectively creating a high impedance barrier. Thus, the diode does not conduct current under reverse bias (except for a tiny leakage current or avalanche breakdown at high voltage).
This topic was automatically created to facilitate community discussion about this exam question. Feel free to share study tips, memory tricks, or additional explanations!