Talk:Electron mobility

message: Mobility is defined both as v = µE and v = -µE within the article  — Preceding unsigned comment added by 2A01:E0A:8F7:4370:3528:469C:E0CC:25E9 (talk) 08:25, 5 July 2022 (UTC)
thread_title: Sign issue

message: I propose merging this article with Electrical mobility. I think that article is more fundamental (after all, both electron and ion mobility fall under it), and since they are both stubs (and repeat themselves a lot), there should just be one article. IlyaV
:I don't think they should be merged. It seems to me that the physics is quite different. The comunities are different, too. I propose to make a reference. (Kehrli (talk) 21:39, 10 June 2009 (UTC)
replies: text: In principle, electron mobility is a special case of electrical mobility. But it's a very important and distinctive special case, enough to warrent its own article. I know this article, right now, is small enough to be part of electrical mobility. But it needs a lot of room to grow, with many topics that are part of electron mobility but not relevant to any other type of electrical mobility--topics like the equations for scattering from phonons, charged defects, uncharged defects, and other electrons, how it affects transistor switching times, and on and on. So I think they shouldn't be merged. But a short summary of this topic should be present in electrical mobility, with a "main article" link. --Steve (talk) 05:18, 11 June 2009 (UTC)
replies: text: More specifically, it seems that electrical mobility mostly describes gases and liquids, so completely different physics. Gah4 (talk) 18:24, 12 April 2018 (UTC)
thread_title: Merge Proposal

message: Looks like the paragraph about Lau's hypothesis was added in March 2007 by 155.69.226.106, somebody from Singapore... The esteemed authors of Lau's hypothesis are also from a Singapore University...  I think this hypothesis may be irrelevant to this wikipedia article, smacks of self-promotion by authors.  Anybody objecting to deleting it? Xenonice (talk) 01:38, 19 January 2008 (UTC)
thread_title: Lau's hypothesis - Original research?

message: I feel that a statement like "typical drift speed in copper" means nothing. First, it was properly defined that mobility gives (linearized) relation between electric field applied and speed of a charged particle. With this in mind ( and without checking I'll just assume mobility in copper is at least on the order of that of silicon) we get, for
a PCB trace of 1mm and voltage difference of 1V => 10V/cm => v ~ 14,000 cm/s, if I'm not mistaken. Much higher than 10^{-4}m/s quoted. Copper will probably melt under these conditions, anyways, but regardless of that, I think that the 'figure' is meaningless.
:I have recently been editing speed of electricity where the drift speed comes up, and yes it is meaningless. It seems to be computed by dividing by the total electron density, but only conduction electrons contribute. But the actual speed of electrons contributing are at the fermi velocity. I suppose you could divide by the actual conduction electron density. Also, some metals have both electron and hole bands contributing to conduction, such as aluminium, and even more, Al is commonly used for power transmission. I suppose there is that it gives an order of magnitude idea of what happens in a metal, that you can compute without the complications of solid state physics, though. Gah4 (talk) 17:10, 19 March 2018 (UTC)
thread_title:  Vague and confusing language 

message: I recently read that low temperature mobilities in GaAs of 14 10^6 cm^2/V s have been reported:
Appl. Phys. Lett. 71, 683 (1997); doi:10.1063/1.119829 (3 pages)
I suggest to change the citation. El perseguidor (talk) 18:16, 13 March 2010 (UTC)
thread_title:  The highest mobility 

message: Looks like the Hall voltage in "Hall_Effect_Measurement_Setup_for_Electrons" is wrong polarity. Electrons pile up on left side of sample and yet Vh is still shown as positive on the left just the same as the setup for holes illustration!  — Preceding unsigned comment added by 71.139.160.159 (talk) 21:17, 18 March 2012 (UTC)
replies: text: I agree, I just switched it. I suspect that the author was trying to indicate how the sign of VH is defined. Either that or a silly mistake. Anyway, you might need to refresh the page to see my new version. --Steve (talk) 22:20, 18 March 2012 (UTC)

text: Oh sorry I missed that...fixed! --Steve (talk) 12:08, 27 March 2012 (UTC)
thread_title:  Is the illustration wrong?  

message: While the equations written down are approximately true for n-type and p-type semiconductors, for any material where both electron and holes are dominant carriers you can't find the hall voltage or mobility of each using the hall effect. The best you can do is for an intrinsic semiconductor where n=p, where you can find the hall mobility times the hall scattering factor, by the usual hall coefficient times conductivity.
:For an interesting case, aluminium has both electron and hole bands. At high magnetic fields, the hall coefficient goes positive.  But otherwise, it has significant electron and hole bands contributing, and so partially cancelling for hall voltage. Gah4 (talk) 16:56, 19 March 2018 (UTC)
thread_title:  Mobility and Hall Effect Poorly Written 

message: I recently added to Talk:Hall effect: 
It seems that Beryllium, Cadmium, Cerium, Iron, Molybdenum, Tungsten, and a few other metals, have positive Hall coefficients. With one valence electron, it is most likely to have a half full band.  (Complicated by crystal symmetry and such, but usually ...)  With two valence electrons, it could be a full band (insulator), or two bands more and less than half full. Note also that the metals with positive Hall coefficient also tend to have high resistivity. With one hole and one electron band, the sign will depend on which one is more, and which one is less, than half full, and the mobilities in each. Aluminum has three valance electrons, which can partially fill three bands. So, some hole and some electron bands, and they change with magnetic field. At high magnetic field, Hc of Al goes positive, but is always the result of both holes and electrons. Gah4 (talk) 18:21, 12 April 2018 (UTC)
thread_title:  Positive Hall coefficient 

message: In the fourth paragraph from the top, the author tries to explain why the electron mobility is an unimportant factor to examine for metal conductivity. 
To quote "Conductivity is proportional to the product of mobility and carrier concentration. For example, the same conductivity could come from a small number of electrons with high mobility for each, or a large number of electrons with small mobility for each. For metals, it would not typically matter which of these is the case, since most metal electrical behavior depends on conductivity alone. Therefore mobility is relatively unimportant in metal physics".
Now, because most metals have high mobility, therefore, conductivity depends on carrier concentration alone and that's why mobility is not so important. Therefore, the word "conductivity" (see above in quoted paragraph in bold ) in bold should be replaced with "carrier concentration" in the second last line of the paragraph. Otherwise, with the current version, it seems like the author is saying that the conductivity of the metals depends on the "conductivity" alone, which doesn't mean anything. 
Please let me know if I am mistaken in my thought process.
Thanks  — Preceding unsigned comment added by 74.70.220.40 (talk) 23:03, 16 November 2019 (UTC)
replies: text: Hmmm. In semiconductors, carrier concentration is relatively low, and its value is often important. The turn-off time for a bipolar transistor, maybe for an FET, too, depends on how fast you can get carriers out, which depends on mobility, since it is concentration that you are trying to get low. In metals, carrier concentration is pretty much constant, and doesn't depend, for example, on current. If carrier concentration is constant, then it is mobility that determines conductivity, which is much higher than in semiconductors. Gah4 (talk) 01:56, 17 November 2019 (UTC)
thread_title:  Regarding why mobility is relatively unimportant in metal physics. 

message: The article says that alloy scattering can only happen in ternary or higher alloys.  Seems to me that it should also happen in SiGe alloys, which are binary alloys.  Otherwise, yes, for III-V compound semiconductors is is ternary and higher. Gah4 (talk) 08:27, 16 December 2019 (UTC)
thread_title:  ''can only happen in ternary or higher alloys'' 

message: Previously classical version of the Einstein relation was used. For most metals, one needs a quantum version with temperature replaced by the Fermi energy. I did a minimal change, but the text should better be improved. Daniel Antonenko (talk) 18:30, 4 July 2023 (UTC)
thread_title:  Einstein relation (classical case not relevant for metals)