P N Junction

• LEDs are heavily doped: They are designed with heavy doping to increase recombination efficiency and light emission.
• Correct description: LEDs emit spontaneous radiation under forward bias, but the doping is intentionally heavy, not light.

Why other options are correct:

• A: Forward bias reduces the depletion width by neutralizing the barrier potential.
• B: Reverse bias widens the depletion region and increases the barrier potential.
• C: Photodiodes operate in reverse bias to detect light by measuring leakage current.

Key Point: The error in D lies in the "lightly doped" claim, which contradicts standard LED design principles.