NEETPhysicsSemiconductors
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): A Zener diode is lightly doped, resulting in a wide depletion region. Reason (R): A narrow depletion region in a p-n junction leads to a very high electric field across the junction even for a small reverse bias voltage, which helps in Zener breakdown. In the light of the above statements, choose t
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
D. (A) is not correct but (R) is correct
Step-by-step solution
A Zener diode is fabricated by heavily doping both the p -side and the n -side of the junction. This heavy doping results in a very thin depletion region (less than 10⁻⁶ m ), making the Assertion (A) incorrect. Because the depletion region is very thin, the electric field across the junction ( E = V d ) becomes extremely high even for a small reverse bias voltage. This high electric field is strong enough to pull valence electrons from the host atoms, causing Zener breakdown. Thus, the Reason (R) is a correct state