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This question might get down votes, I presume, because it has already been asked before but I will still go for it.

In terms of doped Silicon:

Donor atom releases its 5th electron (and gets excited to conduction band) after some thermal energy occurs. Acceptor atom accepts extra electron after some thermal energy occurs (so the valence bond is satisfied). Acceptor atom becomes negatively charged ion. Donor atom becomes positively charged ion.

1.) After electrons are excited in conduction band and valence bonds are bonded, what happens next? Electrons flow out of the semiconductor bar, and new ones come inside?

2.) What is the point of transporting extra electron in conduction band if those extra electrons get to be pushed away from the semiconductor bar after specific amount of voltage is applied?

3.) Is it important for me to understand this in details if I want to become well-educated electrical engineer?

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    $\begingroup$ if you mean asked before on this site, can you provide a link and maybe comment on the problem you have with the answer. (Otherwise questions don't need to be fundamentally orginal for this site) $\endgroup$ – JMLCarter Dec 26 '16 at 23:48
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    $\begingroup$ Q3 is very much off topic here, as it's about career advice $\endgroup$ – Kyle Kanos Dec 26 '16 at 23:52
  • $\begingroup$ Possible duplicate of Conduction of semiconductors at atomic levels $\endgroup$ – user137289 Dec 26 '16 at 23:56
  • $\begingroup$ Same poster asked question 300956. My advice: read a book about this. $\endgroup$ – user137289 Dec 26 '16 at 23:58
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The action of donor and acceptor atoms is part of the doping process, mnufacturing the device. (I believe the valence bonds, which are chemical bonds are also part of this stage) 1) when the conduction band is driven/excited (by an emf when the device is used) electons flow though the doped region, but their behaviour is affected. 2) the pushing can have an affect like a throttle on the flow, allowing it to be regulated. 3) It's not so complicated in principle, I would persevere.

This is theory which will help you understand manufacture of devices in silicon. If you are to work in that area you will need this. Probably people would expect an EE to understand it. However, there are many areas of electrical engineering which require silicon devices to be selected and combined. When working in this way EE don't directly use what was learnt about doping, although it is excellent background. Still I wouldn't like to suggest ducking it, may be unwise. Rock the boat and find someone who can teach. ((small font) I/we am not responsible for any life changing decisions you might or might not make based on my/our opinion disclaimer etc etc).

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  • $\begingroup$ One more thing. Are electrons in conduction bands of atoms, after voltage is applied, moved into interatomic space (or however is it called) of the semiconductor bar or electrons stay bonded to the conduction band (so the last band) of atom? $\endgroup$ – Keno Dec 27 '16 at 13:33
  • $\begingroup$ Normal use is to keep them in the conduction band so the material physically steers the flow. If their energy is such that they can move into inter-atomic space it can be high enough that some electrons can leave the medium altogether, creating problems for electronic applications. $\endgroup$ – JMLCarter Dec 27 '16 at 18:38
  • $\begingroup$ Then how can be true that after voltage is applied, the electrons "flow" through the media? $\endgroup$ – Keno Dec 27 '16 at 19:08
  • $\begingroup$ If they stick to their parent atom and not "leaping off" the outer shell of the atom? $\endgroup$ – Keno Dec 27 '16 at 19:10
  • $\begingroup$ The conduction band extends between multiple atoms. Electrons in that region are thus not bound to a specific atom. Which is to say another way that if the energy of an electron is in the conduction band it can be shunted along to by another electron moving into its vicinity. This is what makes the material a conductor. $\endgroup$ – JMLCarter Dec 27 '16 at 21:18

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