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A pn junction that radiates energy as light is called a ______.
LED
Photo-diode
Photocell
Zener diode
LED
A light-emitting diode (LED) is a p-n junction diode that emits light when forward-biased. It converts electrical energy directly into optical energy through the process of electroluminescence.
A light-emitting diode (LED) is a p-n junction diode that emits light when forward-biased. It converts electrical energy directly into optical energy through the process of electroluminescence.
EgтАЛ=h╬╜=╬╗hcтАЛ тАФ Relation between band gap energy and emitted light wavelength
P=IV тАФ Electrical power input to the diode
When forward biased, electrons from the n-region and holes from the p-region move toward the junction. As these charge carriers recombine across the band gap (EgтАЛ), energy is released in the form of photons. The wavelength of the emitted light depends on the band gap energy of the semiconductor material, given by ╬╗=EgтАЛhcтАЛ.
LEDs utilize direct bandgap semiconductors like Gallium Arsenide (GaAs) or Gallium Phosphide (GaP).
They operate in forward bias mode, allowing current to flow and carrier recombination to occur.
The color of the light is determined by the semiconductor material's bandgap.
High luminous efficiency
Long operational lifespan
Fast switching capability
Low power consumption
Sensitivity to high temperatures
Requires precise current limiting resistors
Indicator lamps and status displays
Optical fiber communication
General lighting and backlighting
Photo-diodes operate in reverse bias and convert light into current, whereas LEDs convert current into light.
Zener diodes are designed for voltage regulation in reverse breakdown mode.
A is correct тАФ An LED is a semiconductor device that emits light through the recombination of electron-hole pairs at a forward-biased p-n junction.
Always remember: LEDs need forward bias for light emission, while photo-diodes and solar cells (photocells) are typically used in reverse bias or zero bias to detect/generate energy from light.