Question
Download Solution PDFGeneration of light in LED is based on which principle?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
- LED (Light Emitting Diode) is a p-n junction diode.
- Under the unbiased condition, the built-in potential barrier prevents the excess free electrons on the n-side from diffusing it to the p-side.
- When the p-n junction is forward-biased, the built-in potential barrier is reduced. This allows the electrons from the n-side to move to the p-side.
- Electron and hole recombination takes place in the junction region within the device. The transition of electrons from a high energy level into a low energy level causes the emission of light (photons). This phenomenon is termed as spontaneous emission.
- This is explained with the help of the following diagram:
Note:
Stimulated emission requires an external energy source to first make the electron jump to a higher energy level. This electron then returns to a lower level releasing a new photon.
The process of stimulated emission is best explained with the help of the following diagram:
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