I know about p-type semiconductors and that there are holes as majority carriers present in the semiconduction. If we apply current through this semiconductor electrons from the valence band will come, to occupy the holes thus leaving a hole behind them, so we can say that the hole creates a current. Now what confused me is that those holes can not escape the semiconductor crystal itself, so how is current possible. Or do valence electrons leave because of attraction from the positive terminal of the battery?

Please help me understand this

  • \$\begingroup\$ Thought experiment that may shed light: when a hole reaches an ohmic contact and a metallic electron fills it, did it manage to produce meaningful current in the metal? \$\endgroup\$
    – nanofarad
    Jun 30, 2022 at 20:33
  • \$\begingroup\$ But if an electron comes in. Isn´t it, that one must go out from the other side? \$\endgroup\$ Jun 30, 2022 at 20:39
  • \$\begingroup\$ Yes, but you have a closed circuit and related current at the opposite end. \$\endgroup\$
    – nanofarad
    Jun 30, 2022 at 21:43

1 Answer 1


It is more complicated than that.

At equilibrium, the Fermi level of the semiconductor is equal to the Fermi level of the conductor->so the valence band of the p type semiconductor has the same energy as the conduction band of the conductor.

That's why an electron transfer is possible from the semiconductor to the conductor.

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