Physics - Semiconductors Question with Solution | TestHub
Which of the following statement is NOT correct in the case of LED?
(A) It is a heavily doped p-n junction diode.
(B) It emits light only when it is forward biased.
(C) It emits light only when it is reverse biased.
(D) The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used.
Options:
Answer:
Solution:
A Light Emitting Diode (LED) is a heavily doped p-n junction diode which under forward bias emits spontaneous radiation.
When the diode is forward biased, electrons are sent from n p (where they are minority carriers) and holes are sent from p n (where they are minority carriers). At the junction boundary, the concentration of minority carriers increases compared to the equilibrium concentration. Thus, at the junction boundary on either side of the junction, excess minority carriers are there which recombine with majority carriers near the junction.
On recombination, the energy is released in the form of photons. Photons with energy equal to or slightly less than the band gap are emitted.
Therefore, an LED emits light only when it is forward biased. The statement that it emits light only when it is reverse biased is incorrect.
Answer: C
