Please help. In reverse bias we say the negative terminal of the battery attracts holes of the p-type hence depletion zone becomes bigger. Why don't electrons from the negative side of the battery actually move to go and fill the holes then repel electrons in the n-type through the wire and to the battery creating a current in reverse bias?!

Depletion zone is made by electrons from n-type going to p-type then surely electrons from the battery could travel to the holes in the p-type as well instead of just ATTRACTING the holes. Please can someone explain this it is really confusing me.

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    \$\begingroup\$ Not as confusing as one long sentence... \$\endgroup\$
    – Trevor_G
    Commented Oct 20, 2017 at 16:41
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    \$\begingroup\$ @Moe Entitled much? \$\endgroup\$
    – Cuadue
    Commented Oct 20, 2017 at 17:08
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    \$\begingroup\$ Welcome to EE.SE, @moe. Please use proper paragraph and sentence formatting including capital letters and punctuation. It helps legibility, clarity and credibility. Pay attention to the comments and try and address the issues raised, respecting those who help you here for no reward and no cost to you other than some keyboard discipline. If you don't care you'll find that you won't get good answers. Fix your post? \$\endgroup\$
    – Transistor
    Commented Oct 20, 2017 at 17:12
  • \$\begingroup\$ Is this a homework question? \$\endgroup\$
    – Oskar Skog
    Commented Oct 20, 2017 at 17:44
  • \$\begingroup\$ No. I was simply looking at how the PN junction works in a diode and thought about it. \$\endgroup\$
    – Moe
    Commented Oct 20, 2017 at 17:48

1 Answer 1


It is the presence of holes and extra electrons in the semiconductor material that make it conductive. At the join between the layers in a PN junction the holes and electrons join together and cancel each other out creating that depletion layer which is an insulator.

When you attach a reverse voltage you force the holes and electrons to go towards each other which fills in more holes in the depletion layer making it wider and a better insulator.

Attaching a forward voltage pulls the electrons out of the holes in the depletion layer till it is no longer an insulator.

There are a good description here with some illustrations.


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