Advertisements
Advertisements
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 band gap of an LED, if it is required to emit light in the visible range? Draw a circuit diagram and explain its action.
Advertisements
उत्तर
While fabricating a pn-junction diode to be used as LED, the important consideration which are to be taken
are as follows:
(i) It should be heavily doped.
(ii) It should be forward biased.
(iii) It should be encapsulated with a transparent cover so that emitted light can come out.
(iv) It must have a proper band gap so that the emitted radiations lie in the visible region.
LEDs that can emit red, yellow, orange, green and blue light are commercially available. The semiconductor used for fabrication of visible LEDs must at least have a band gap of 1.8 eV (spectral range of visible light is from about 0.4 μm to 0.7 μm, i.e., from about 3 eV to 1.8 eV). The compound semiconductor Gallium Arsenide – Phosphide (GaAs1–xPx) is used for making LEDs of different colours. GaAs0.6 P0.4 (Eg ~ 1.9 eV) is used for red LED.
APPEARS IN
संबंधित प्रश्न
With the help of a neat circuit diagram, explain the working of a photodiode.
How is a photodiode fabricated?
Draw the circuit diagram of a full wave rectifier using p-n junction diode.
Explain its working and show the output, input waveforms.
What happens to the width of depletion player of a p-n junction when it is (i) forward biased, (ii) reverse biased?
Draw the circuit diagram of an illuminated photodiode in reverse bias. How is photodiode used to measure light intensity?
Draw the circuit arrangement for studying the V-I characteristics of a p-n junction diode in reverse bias. Plot the V-I characteristics in this case.
The wavelength and intensity of light emitted by a LED depend upon ______.
Consider the following statements (A) and (B) and identify the correct answer.
- A Zener diode is connected in reverse bias when used as a voltage regulator.
- The potential barrier of the p-n junction lies between 0.1 V to 0.3 V.
In Figure, assuming the diodes to be ideal ______.
A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is 1.42 eV. The wavelength of light emitted from the LED is ______.
