Step 1: Understanding the Concept:
In a p-n junction diode, reverse bias occurs when the n-region is connected to a higher potential than the p-region. This increases the barrier height, preventing majority carrier flow but allowing a small number of minority carriers to cross.
Step 2: Key Formula or Approach:
The reverse current consists of a reverse saturation current due to minority carriers. At a high enough reverse voltage (Breakdown voltage), the current increases sharply due to Zener or Avalanche breakdown.
Step 3: Detailed Explanation:
Assertion A is correct: In reverse bias, a very small "reverse saturation current" flows, which is nearly constant until the breakdown voltage is reached. At breakdown, the current increases drastically.
Reason R is incorrect: Below the breakdown limit, the current is due to minority charge carriers, not majority carriers. Majority carriers are pushed away from the junction in reverse bias. Above the critical voltage, current increases due to carrier multiplication or tunneling, but the statement about majority carriers flowing below the limit is fundamentally wrong.
Step 4: Final Answer:
Assertion A is true, but Reason R is false.