Question

LED is a p-n junction diode which is
A: forward biased
B: either forward or reverse biased
C: reverse biased
D: neither forward biased or reverse biased

Answer 1

Hint: As we know, LED is a light emitting diode that produces light. The production of light and its intensity is determined by the flow of current. Keeping this point in mind, we can approach this question.

Complete Step by step answer: LED is a p-n junction diode. As we know, when a p type semiconductor is suitably joined with an n type semiconductor, we obtain a p-n type semiconductor. The contact surface is termed a p-n junction. In a p-n junction diode, diffusion of particles leads to the formation of a depletion layer and a potential barrier that prevents further flow of particles.
In LEDs, the recombination of charge carriers take place. The holes from P side and the electrons from the N side combine to give energy in the form of heat and light. This is possible only when forward bias takes place.

In forward biasing, the external voltage is delivered across the P-N junction and this overcomes the potential barrier. A negative voltage is applied to N type and a positive voltage on the P side. When this occurs in LED , free electrons in the conduction band recombine with holes in the valence band. This leads to energy emission,
Hence, the LED is forward biased.

Therefore option A is the correct answer among the given options.

Note: Silicon is a widely used semiconductor as it is less sensitive to temperature difference but it is not used to make LED as it emits energy in the form of heat and not light. Hence other materials like Indium Gallium Nitride and aluminium gallium indium phosphide are used.