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Special Purpose P-n Junction Diodes - LED

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Estimated time: 3 minutes
CBSE: Class 12

Key Points: LED

  • LED emits visible light or invisible infrared light when forward-biased.
  • LEDs which emit invisible infrared light are used for remote controls.
  • Types of LED materials and their colours:
  • GaAs - infrared; GaAsP - red to infrared, orange
  • GaP - red, yellow, green; AlGaP - green
  • GaN - green, emerald green; GaInN - near ultraviolet, bluish-green, blue
  • SiC - blue (as substrate); ZnSe - blue; AlGaN - ultraviolet
  • AlGaAsP - high-brightness red, orange-red, orange, yellow
  • The energy band diagram shows a forbidden gap between conduction and valence bands - emitted photons correspond to this gap energy.
  • LED I–V characteristics show different curves for Red (R), Yellow (Y), Green (G), and Blue (B) - the higher the frequency of light, the higher the threshold voltage.
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