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Why is it that "hole" conductivity is called so, isn't that just a case of electron movement in the opposite direction, or as in 'Vacant Seats in Theater' analogy mentioned in the Electron Hole Wikipedia, it can be thought of as people moving in opposite direction?

I am not looking for a long explanation, just curious why would textbooks/theory prefer mentioning something fictitious rather than something real which is electron movement?

Is it because it helps distinguishing the conduction due to normal electron movement vs movement due to lack of it? Probably when you visualize it, it does indeed look like movement of holes as well. I was really not able to understand the rationale, hence this somewhat basic question.

As a side note, did anyone have this question while learning? I hardly saw any discussion on however I thought it is a good question to ask.

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You are correct that the only thing moving in a metal or semicondcutor is electrons, but also that the behaviour of a hole and an electron is different. A couple of ways in which this is important for electronic engineering (as opposed to solid state physics) are:

  • At a PN junction. In the semiconductor far from the junction, the behaviour is pretty much the same whether there are hole or electrons doing the work. But at the junction they can meet, and when they do, the electron falls into the hole. Or to use the technical term, the electron and hole recombine.
  • In a hall sensor. Electrons and holes which are moving are pushed sideways by magnetic fields. They have opposite charges and are flowing in opposite directions, so they are pushed the same way. But because they have opposite charges they create opposite voltages. The hall voltage in a P type semiconductor is in the opposite direction to the hall voltage in an n type or a metal.

Also, if you get stuck into the physics of conduction in metals and semiconductors, you quickly find that the quantum nature of electrons mean that you can't really think of individual electrons or holes moving about. The real physical insights come from something called a Fermi surface. The idea of electron surfaces and hole surfaces is key to those insights, so after learning about them, the "electron" and "hole" terms seem more natural.

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I remember discussing this question during my studies for a long time. The 'holes' are electrons 'missing' in the valence band, and not in the conduction band. So an atom with all its electrons in the valence band 'gives' its electron to that one with a 'hole'.

The free electrons on N materials, on the other hand, are in the 'conduction' band.

Since those electrons in the valence band are closer to the nucleus than the electrons in the conduction band, their mobility is more difficult and that is why for the same size, an N-channel transistor is a much better conductor than a P-channel transistor.

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The answers here are skipping one important feature: A hole is not a missing electron. A hole is a semiconductor atom which has extra protons in relation to its electrons.

A hole is a genuine positive charge. When a hole moves, a positive charge has adopted a new location.

Take the simple case of neutral hydrogen atoms. If we remove one electron, we're left with a bare proton: a positive charge. A proton is not a "missing electron." Positive charge is not a "lack of electrons," instead it's a genuine type of charge in it's own right.

The OP question would be valid if silicon was made of electrons only. Then, any "hole" would just be a gap in the population of electrons, and if the hole moves, it's really just electrons moving backwards. But silicon is made of cancelled-out charge: equal positive and negative charges. A "hole" is a gap in the electron population which exposes a hidden proton. A hole is a genuine positive charge.

With the movie-theater analogy, the complete picture would be to place red light bulbs on all the seats. These are the protons. Now let the audience of electrons sit on the seats and cover the lights. If there are any gaps in the audience, then in the dark theater we will see brilliant red lights at the location of "positive charges." These are the red lights which haven't been canceled out by an electron. If one person changes seats, then the location of the red light will move the other way.

So that's the answer: at the micro-level, yes, electrons are shifting in order to cover or reveal the positive charges. But from a distant view, there are no electron shifts. They are indetectable, unimportant. It's the changing position of the positive charges which dominate. All we see in the dark movie theater are some extremely powerful red lights which suddenly leap from one seat to the next.

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  • \$\begingroup\$ Thanks, @wbeaty. Happy to see your answer here! I really like your articles on such fundamental questions at amasci.com. Really the type of material I am looking for. In fact, I have bookmarked many of the articles you had written to read when I get time! \$\endgroup\$ – Nishant Oct 13 '18 at 9:46
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Basically, hole is vacancy of electron. So when electron moves hole is created. Electron is negatively charged(at negative or low voltage) and hence attracted(move) towards positive terminal of battery, which means holes moves towards negative terminal of battery which is same as the direction of current(+ to -). That is why we say holes(vacancy of electrons) are contributing to the current.

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  • \$\begingroup\$ Yeah but my specific question is why is it good to describe in terms of a fictitious thing over a real thing. Even the convention of current is a legacy thing :) \$\endgroup\$ – Nishant Sep 15 '16 at 9:08

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