PN junctions and diodes

Which diode, made from a PN junction very heavily doped on both sides, shows a negative-resistance region where current decreases as forward voltage increases?

  1. ASchottky barrier diode
  2. BPIN diode
  3. CTunnel diode (Esaki diode)
Show answer and explanation

Answer: C. Tunnel diode (Esaki diode)

A tunnel diode is a PN junction doped so heavily on both sides that it is degenerate. Its depletion layer is very thin, so tunneling current flows at low forward voltages. As voltage increases, the tunneling current falls, creating a negative-resistance region used for high-frequency oscillators. It is also called the Esaki diode after its discoverer, Leo Esaki.

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