Reverse bias increases the depletion region (the "space charge region"). Remembering that electrons travel from (-) to (+) terminal, and that in reverse mode the (+) terminal is attached to the n-doped side of a PN junction, I would expect that current generation through avalanche breakdown is occuring due to majority carriers.

PN junction in equilibrium (source)

What am I missing here?

  • \$\begingroup\$ It's the depletion region, there are no majority carriers. \$\endgroup\$ Dec 7, 2014 at 22:11
  • \$\begingroup\$ @GeorgeHerold, you're suggesting that avalanche occurs in the depletion region? why? and if the term "majority carrier" is undefineable in the depletion region, so does the term "minority carrier", no? \$\endgroup\$
    – Sparkler
    Dec 7, 2014 at 22:22
  • \$\begingroup\$ Where else can it occur? It's conducting elsewhere. \$\endgroup\$ Dec 7, 2014 at 22:58
  • \$\begingroup\$ @GeorgeHerold, to my understanding, avalanche, or rather impact ionization, occurs anywhere, but at a high reverse bias it's becoming significant. \$\endgroup\$
    – Sparkler
    Dec 7, 2014 at 23:03
  • \$\begingroup\$ Yeah, not many carriers in the depletion region. You can't get a high reverse bias except where there are no free charges. (Well, you can't get much forward bias where there are free charges either.) \$\endgroup\$ Dec 7, 2014 at 23:11

1 Answer 1


The majority carriers operate when the PN junction is forward biased. The minority carriers operate when the PN junction is reverse biased. Since avalanche breakdown occurs when the PN junction is reverse biased, it can only be caused by the minority carriers. Therefore, it is correct to say that avalanche breakdown is caused by minority carriers.


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