Question
What property of an LED’s semiconductor material determines its forward voltage drop?
Answer Options
- A) Intrinsic resistance
- B) Band gap
- C) Junction capacitance
- D) Junction depth
Correct Answer: B
Explanation
A Light Emitting Diode (LED) emits light when current flows through its forward-biased junction. This process involves electrons dropping from a higher energy state to a lower energy state, releasing energy in the form of a photon (light). The energy difference between these two states is the fundamental characteristic of the material.
This energy difference is called the band gap of the semiconductor material. The energy of the emitted photon (which determines the color of the light) is directly proportional to the band gap energy. Consequently, the band gap energy also dictates the amount of energy (voltage) that must be supplied to the junction to enable the electron transitions. Thus, the band gap determines the LED’s forward voltage drop, with blue and white LEDs having higher drops than red or infrared ones.
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