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Good electron-hole conductor?

by Stanley514
Tags: conductor, electronhole
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Stanley514
#1
Feb21-13, 08:46 PM
P: 300
Which materials exhibit good electron and hole conductivity in the same time?
And which of them are cheap and available?
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marcusl
#2
Feb21-13, 09:07 PM
Sci Advisor
PF Gold
P: 2,080
Silicon meets all of the requirements you have listed.
Stanley514
#3
Feb21-13, 09:16 PM
P: 300
Silicon meets all of the requirements you have listed.
Something much better than intrinsic semiconductors?I need hole conductivity comparable to electron conductivity in metals.And electronic conductivity too.

chill_factor
#4
Feb22-13, 01:10 AM
P: 896
Good electron-hole conductor?

sure. Tungsten conducts electricity through holes and this is shown through the Hall coefficient being negative.
Stanley514
#5
Feb22-13, 05:59 AM
P: 300
Tungsten conducts electricity through holes and this is shown through the Hall coefficient being negative.
Seem to be wrong.
The negative Hall coefficient indicates that electrons are the charge carriers
www.phys.utk.edu/labs/modphys/Hall%20Effect.pdf
I was not able to find any mention in In-et that Tungsten is hole conductor.
Could you give any link about it? I need some material that is electrone-hole conductor at room temperature and could conduct holes in all directions under usual circumstances.
DrDu
#6
Feb22-13, 06:55 AM
Sci Advisor
P: 3,593
Probably all the semi-metals, e.g. Bismuth.
M Quack
#7
Feb22-13, 08:08 AM
P: 662
what do you need this for? Understanding the question better will (hopefully) result in better answers...
Stanley514
#8
Feb22-13, 10:29 AM
P: 300
what do you need this for? Understanding the question better will (hopefully) result in better answers...
New concepts are not allowed to reveal and discuss here.
But I phrased my question clear enough.
Darwin123
#9
Feb22-13, 04:44 PM
P: 741
Quote Quote by Stanley514 View Post
Which materials exhibit good electron and hole conductivity in the same time?
And which of them are cheap and available?
You may be looking for a semimetal.

Arsenic, antimony, and bismuth are semimetals that are cheap and available.
Be very careful working with that arsenic.

Graphite is usually found in multicrystal form. I don't think the multicrystal form is a good conductor. Single crystal graphite are quite expensive. However, graphite would be safe.

Alpha-tin may be interesting. There may be a temperature issue.

Here is a link and quote on semimetals.
http://en.wikipedia.org/wiki/Semimetal
“The semimetallic state is similar to the metallic state but in semimetals both holes and electrons contribute to electrical conduction. With some semimetals, like arsenic and antimony, there is a temperature-independent carrier density below room temperature (as in metals) while, in bismuth, this is true at very low temperatures but at higher temperatures the carrier density increases with temperature giving rise to a semimetal-semiconductor transition.

The classic semimetallic elements are arsenic, antimony, bismuth, α-tin (gray tin) and graphite, an allotrope of carbon.”
Darwin123
#10
Feb22-13, 04:56 PM
P: 741
Quote Quote by Stanley514 View Post
Which materials exhibit good electron and hole conductivity in the same time?
And which of them are cheap and available?
You may also find some “narrow gap semiconductors” that are useful in their intrinsic (nearly pure) form.

A narrow gap semiconductor would be an insulator at absolute zero. However, the band gap is small. If the band gap is small enough, thermal excitations will produce both electrons and holes even at room temperature. Therefore, a narrow band semiconductor would be a lot like a semimetal.

I made a mistake in another post. Grey tin is a narrow gap semiconductor, not a semimetal. For your purposes, they may be the same. After all, both narrow gap semiconductors and semimetals have both conduction-electrons and valence-holes at room temperature.

Other narrow gap semiconductors include PbS, InAs,, HgCdSe, PbSe. A bigger list is found in the following link.

http://en.wikipedia.org/wiki/Narrow-gap_semiconductor
“Narrow gap semiconductors are semiconducting materials with a band gap that is comparatively small compared to silicon. They are used as infrared detectors or thermoelectrics.”

I discussed semimetals in a separate post.
DrDu
#11
Feb23-13, 01:43 AM
Sci Advisor
P: 3,593
Quote Quote by Darwin123 View Post
Grey tin is a narrow gap semiconductor, not a semimetal.
Are you sure?
Stanley514
#12
Feb23-13, 08:41 AM
P: 300
As I know the best hole mobility among pure semiconductors has Grmanium.But it still not too high.Do not know about semimetals.Maybe you could give link with exact data?I know that excellent hole conductivity is expected for graphene,but it is rare and expensive.What would be approx. price of one-crystall graphite?Is it brittle?I need material with hole conductivity which would be comparable to at least electron conductivity in carbon.Also graphite as I know,doesn't conduct current in all directions.Only in one of them it seems.I was not able to find any clear mentioning in In-et about hole conductivity in graphite.
One more question: what is the max. voltage that p-type semiconductors are able to withstand?
Darwin123
#13
Feb23-13, 12:07 PM
P: 741
Quote Quote by DrDu View Post
Are you sure?
No.

I am doing a search on it. However, I get answers that vary with the reference.

Here is on link and quote on the subject of grey tin. I don’t know what the author is talking about. I had thought that the electronic structure determines whether a material is a semiconductor or semimetal.

http://en.wikipedia.org/wiki/Metalloid
“Grey tin has the same crystalline structure as that of the diamond allotrope of carbon. It behaves as if it was a semiconductor (with a band gap of 0.08 eV) but has the electronic band structure of a semimetal.[361] It is sometimes referred to as a metalloid.”


The author here implies that there is a definition for semimetal that does not incorporate electronic structure.

Now I am curious. Could someone help me out here? How should grey tin be classified, exactly?

Regardless, grey tin is a material which at higher temperatures has both electrons and holes. However, grey tin is unstable at room temperature. Therefore, grey tin probably doesn't satisfy the requirements of the original poster (OP).
DrDu
#14
Feb23-13, 01:25 PM
Sci Advisor
P: 3,593
Quote Quote by Darwin123 View Post
No.

“Grey tin has the same crystalline structure as that of the diamond allotrope of carbon. It behaves as if it was a semiconductor (with a band gap of 0.08 eV) but has the electronic band structure of a semimetal.[361] It is sometimes referred to as a metalloid.”
I think he is maybe referring to a direct band gap of 0.08 eV . Semimetals often have a vanishing indirect band gap but a non-vanishing direct band gap, i.e. there are electron and hole pockets.
These band structures are lately of great interest as spin orbit coupling may lead to topological insulators.
Stanley514
#15
Feb24-13, 05:23 PM
P: 300
It is claimed that some metals (such as Iron) have positive Hall coeficient.But it seems that Hall effect is observed in strong magnetic fields only.Does it mean that in absence of strong fields Iron will have very small hole conductivity?
DrDu
#16
Feb25-13, 02:35 AM
Sci Advisor
P: 3,593
No, the type of charge carriers is independent of the field. You only need the field for diagnostic purposes. However I would be careful with the interpretation of the Hall coefficient in terms of nature of the charge carriers.
Kholdstare
#17
Feb25-13, 11:04 AM
P: 390
You need to look for a conductor which has the value of (carrier conc. x avg. mobility) same for both electrons and holes. I don't think such thing naturally exists.
Kholdstare
#18
Feb25-13, 11:33 AM
P: 390
I think you need a conductor for which (carrier conc. x avg. mobility) is same for both electrons and holes. That kind of thing does not exist naturally

EDIT: Damn forgetful mind.


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