Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: A diode under reverse-biased condition provides very small current which is nearly independent of voltage until a critical limit at which the current increases drastically.
Reason R: Below the critical voltage limit, only majority charge carriers flow which increases drastically above critical voltage.
choose the correct answer from the options given below:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Evaluate the physical mechanism of a p-n junction diode under reverse bias. The reverse saturation current is created by minority carriers, not majority carriers. The breakdown at high voltages happens due to avalanche or Zener breakdown mechanisms.
Step 2: Key Formula or Approach:
In reverse bias, the depletion region widens, acting as a massive barrier to majority carriers. The small current that trickles through is purely due to minority carriers thermally generated near the junction.
Step 3: Detailed Explanation:
Let's analyze Assertion (A):
Under reverse bias, a p-n junction diode blocks the main current, yielding only a tiny leakage current (in $\mu\text{A}$ or $\text{nA}$). This current remains relatively constant and independent of the applied voltage up to a certain point. When the voltage hits a critical threshold (Zener or Avalanche breakdown voltage), the current suddenly skyrockets. This correctly describes the macroscopic V-I characteristic of a diode. Thus, Assertion A is true.
Let's analyze Reason (R):
Reason R claims that this leakage current is due to the flow of majority charge carriers. This is fundamentally incorrect. The reverse applied voltage pushes majority carriers (holes in p-side, electrons in n-side) away from the junction, increasing the depletion width. The tiny leakage current is actually sustained entirely by the flow of minority charge carriers (electrons in p-side, holes in n-side) sweeping across the junction due to the strong built-in electric field.
Since the fundamental mechanism stated in R is wrong, Reason R is false.
Step 4: Final Answer:
Assertion A is true, but Reason R is false.