PN junction behavior under reverse bias: The voltage at which a reverse-biased diode begins to conduct heavily due to avalanche or Zener effects is called the:

Introduction / Context:
Reverse-biased diodes normally pass only tiny leakage currents. Above a certain negative voltage, however, strong electric fields enable avalanche or Zener tunneling, causing dramatic current increase. Correctly naming this threshold is essential when specifying protection components or reference regulators.

Given Data / Assumptions:

• Standard PN diode under reverse bias.
• We are identifying the voltage where reverse current rises sharply.
• Mechanism could be avalanche (higher voltage) or Zener tunneling (lower voltage), depending on doping.

Concept / Approach:
The term “breakdown voltage” denotes the reverse voltage at which the junction conducts substantially. Zener diodes are designed to operate in this region safely, providing a quasi-constant voltage for regulation. Ordinary signal diodes are not intended for sustained breakdown operation, as it can cause overheating and damage.

Step-by-Step Solution:
Increase reverse bias on a PN junction.At the breakdown threshold, high field enables carrier multiplication or tunneling.Current rises steeply; the associated voltage is the breakdown voltage.Zener devices exploit this region in a controlled way.

Verification / Alternative check:
Examine I–V curves: reverse current remains near-zero until reaching the knee where breakdown occurs and current increases rapidly with slight voltage change.

Why Other Options Are Wrong:
Barrier potential: small forward threshold (~0.7 V Si).Forward voltage: pertains to forward conduction.Biasing voltage: generic term; not the breakdown threshold.

Common Pitfalls:
Assuming breakdown always destroys the device. While true for non-Zener diodes, Zeners are engineered to operate there within power limits.

Final Answer:
breakdown voltage