Question

Which of the following statements is not correct in the case of light emitting diodes (LEDs)?
A. It is a heavily doped p-n junction. 
B. It emits light only when it is forward-biased. 
C. It emits light only when it is reverse-biased. 
D. The energy of the light emitted is equal to or slightly less then the energy gap of the semiconductor used.
Choose the correct answer from the options given below:

• A. C and D
• B. C
• C. B
• D. A

Hint:

For LED behavior:
• LEDs work only in forward bias.
• The emitted photon energy corresponds to the semiconductor’s bandgap.

Answer 1

The Correct Option is B

Let's analyze each of the given statements regarding Light Emitting Diodes (LEDs) to determine which one is incorrect:

1. Statement A: It is a heavily doped p-n junction.
   This statement is correct. LEDs consist of a heavily doped p-n junction to ensure efficient recombination of electrons and holes, which results in light emission.
2. Statement B: It emits light only when it is forward-biased.
   This statement is correct. LEDs emit light only when they are forward-biased because only then do electrons and holes recombine at the junction, emitting energy in the form of photons (light).
3. Statement C: It emits light only when it is reverse-biased.
   This statement is incorrect. In reverse bias, the LED does not emit light; instead, it might get damaged due to breakdown. LED operation is based on forward bias.
4. Statement D: The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used.
   This statement is correct. The photon energy, which corresponds to the color of the emitted light, is roughly equal to the energy band gap of the semiconductor material.

Upon evaluating all statements, it is clear that the incorrect statement is C. Therefore, the correct answer is option C.