Question

The light emitting diode (LED) is :
a. A heavily doped p-n junction with no external bias
b. A heavily doped p-n junction with reverse bias
c . A heavily doped p-n junction with forward bias
d. A lightly doped p-n junction with no external bias
e. A lightly doped p-n junction with reverse bias

Answer 1

HintThis is a logic based question. In the question itself it is sure that the material is a p-n junction. Now we just have to figure out its biasing which we can find out as it is simultaneously working therefore forward bias is most suited. Because of the high efficiency needed we can also get that it should be highly doped.

Complete step-by-step solution:
Firstly we have to properly get what a LED is:
An LED as the term stands is a Light Emitting Diode. It is made up of a semiconductor p-n junction material. We perform specific types of doping on the material to get it work well.
Its characteristics are:
- The light emitted through it is specific directional.
- They can form light from different colours.
- They can also be of various luminous intensity as per the needs
- They are found in various shapes and sizes.
- Temperature will affect the efficiency of a LED.
- It generally has a log life.
- It is low energy consuming.

The structure of the LED has a high level of doping so that it can work on the principle of the interconversion of the light and electricity. It is forward biased though so that it can emit light spontaneously when connected. It reduces the efficiency of an energy barrier.
Therefore the right option is C. A heavily doped p-n junction with forward bias.

Note:
LED is made up of specific semiconductor materials like gallium arsenide $(GaAs)$ and gallium phosphide $(GaP)$. It is so that doping could be done at a high magnitude.