PN junctions and diodes

In a very heavily doped PN junction, what is the main mechanism of breakdown at low reverse voltage?

  1. AAvalanche breakdown
  2. BZener breakdown due to quantum-mechanical tunneling
  3. CMelting of the junction due to heat
Show answer and explanation

Answer: B. Zener breakdown due to quantum-mechanical tunneling

In a junction heavily doped on both sides, the depletion layer is very thin, so electrons in the valence band tunnel through the barrier into the conduction band and current flows. This is Zener breakdown, which occurs at low breakdown voltages of about 5 V or less. At higher breakdown voltages, avalanche breakdown dominates.

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