Why is it not possible to measure the internal potential difference in a p-n diode across the depletion region externally when no external voltage is applied to the diode ?

Steven here https://electronics.stackexchange.com/a/33235 does not elaborate on why the potential difference cannot be measured.


1 Answer 1


Olin alluded to this — if you make contact with the P and N regions of the diode in order to measure the voltage, those semiconductor-to-metal contacts become junctions, too, and the total potential of those extra junctions will exactly cancel the potential of the original P-N junction.

  • \$\begingroup\$ Thanks. I'm not sure how I missed that. But your reply kind of better explained it. \$\endgroup\$
    – GamingX
    Sep 4, 2012 at 23:40

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