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प्रश्न
Write the important considerations which are to be taken into account while fabricating a p-n junction diode to be used as a Light Emitting Diode (LED). What should be the order of the band gap of an LED, if it is required to emit light in the visible range? Draw a circuit diagram and explain its action.
उत्तर
For the formation of LED direct bandgap semiconductors like GaAs, CdS, etc should be used which emits light. The p-n junction should be operated in forwarding bias. Most of the Light is produced in p-area of the device so while fabricating LED this area is kept close to the surface of the diode so that the minimum amount of energy is absorbed. One can use different materials for producing different colored Lights. The semiconductor used for the fabrication of visible LEDs must at least have a bandgap of 1.8 eV. The order of the band gap if it is required to emit light in the visible range is about 3 eV to 1.8 eV.
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संबंधित प्रश्न
With what considerations in view, a photodiode is fabricated? State its working with the help of a suitable diagram.
Even though the current in the forward bias is known to be more than in the reverse bias, yet the photodiode works in reverse bias. What is the reason?
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Forward biasing
How are these characteristics made use of in rectification?
Briefly explain its working. Draw its V - I characteristics for two different intensities of illumination ?
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Draw the circuit diagram of an illuminated photodiode in reverse bias. How is photodiode used to measure light intensity?
Answer the following question.
Draw solar cell V-I characteristics.
With reference to Semiconductor Physics,
Name the process that causes depletion region in a p-n junction.
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If the resistance R1 is increased (Figure), how will the readings of the ammeter and voltmeter change?
Why a photo-diode is operated in reverse bias whereas the current in the forward bias is much larger than that in the reverse bias? Explain. Mention its two uses.
