If a current travels through a semiconductor holes travel to the "end" of a semiconductor, where they can recombine with incoming electrons. Does this also occur if there is no current flowing through the semiconductor so that the holes are at the "end" of it, or is there no hole traveling at all?
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\$\begingroup\$ wikiwand.com/en/Charge_carrier Current is the rate of charge flow. So if no current, nothing moves \$\endgroup\$– Tony Stewart EE75Commented Jun 29, 2022 at 14:12
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\$\begingroup\$ electrons are always in motion..Read about Fermi velocity here: en.m.wikipedia.org/wiki/Fermi_energy \$\endgroup\$– tobaltCommented Jun 29, 2022 at 14:20
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\$\begingroup\$ wikiwand.com/en/Carrier_lifetime discusses recombination effects and for more theory iue.tuwien.ac.at/phd/park/node32.html \$\endgroup\$– Tony Stewart EE75Commented Jun 29, 2022 at 14:31
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2 Answers
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Brownian motion applies to thermally excited electrons (even if they're a bit de-located) as well, so holes do "move" stochastically in non-zero temperatures as well. I write "move" because "hole" is actually "missing occupation in crystal lattice"; and that is quickly remedied by thermally excited change of energy/impulse of electrons, which then changes probabilities elsewhere. (In other words, I'm not a huge fan of the word "move" when it comes to electrons / holes: as long as no photonic recombination is actually observed, this happens on a basis of "shifting occupation probabilities".)
answered Jun 29, 2022 at 14:06
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Current is the average flow of a large number of charged particles, sometimes called their drift, due to the many orders of magnitude slower that this speed is for practical currents compared to their thermal velocities.
All the mobile particles, and here I include both electrons and holes as fully paid-up members of the quantum mechanical particle club (they have effective mass, charge, obey quantum mechanical probabilities), are in constant thermal motion, whether there is a mean drift or not.
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\$\begingroup\$ @Uwe The effective mass of a hole is positive. That is, if there's an electric field accelerating its positive charge to the left, it moves left, all the signs in F=ma are consistent. Don't ask me to actually do QM on holes or electrons though, I just believe the stuff that appears to me to be self consistent in what physicsts tell me. \$\endgroup\$– Neil_UKCommented Jun 29, 2022 at 15:22