About semiconductors

why we use only si & ge..instead of carbon (because it also have 4 valence electrons..)?
IS there any other semi conductors except si and ge?

There are many reasons for that.see link https://wiki.answers.com/Q/Why_carbon_does_not_use_in_a_semiconductor_devices#slide1
May this helps....

Deepthi Palavelli said:

IS there any other semi conductors except si and ge?

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There are a few others, such as Gallium Arsenide and Silicon Carbide.

Deepthi Palavelli said:

carbon

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Good guess. Diamond looks very promising. See here and here.

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hamid159 said:

There are many reasons for that.see link https://wiki.answers.com/Q/Why_carbon_does_not_use_in_a_semiconductor_devices#slide1

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Sorry, the answer given there is complete nonsense.

Many materials systems in IV, III-V, II-VI each with their
own strengths and problems.

Silicon wins on cost and for almost anything sold to the
consumer, cost is first and second.

Diamond is not exactly affordable in single crystal, high
purity, large diameter wafers. In fact you can not have
a 6", 8", 12" (that's 150, 200, 300mm for all you modern
types) wafer of single crystal diamond, nor one with a
semiconductor grade single crystal epi layer, at any
price.

And if you could have one, you would find it very difficult
to do the basics - ohmic contacts I think have only been
demonstrated using exotic metals, implants can't be
activated because the crystal is -too- strong to substitute
them, there is no native oxide, etc.

SiGe is just Si with a dollop of secret sauce. It's advantage
is its silicon compatibility (try integrating 1Mgates with the
RF chain, in a III-V technology).

godfreyl said:

...Sorry, the answer given there is complete nonsense.

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Could you explain why the fact of some others materials presents less conductivity does not answer the raised question ?
As far I know, it explains exactly from a chemical point of view, the reason.

it has a large resistivityaa as compared to si and Ge.and also its conductivity is also large . there have 4 valence electron which are near to nucleus so it required large energy to move electron.so by these reason we are not used as semiconductor....

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it has a large resistivityaa as compared to si and Ge.and also its conductivity is also large

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Point one:
This statement directly contradicts itself. Resistivity is the exact opposite of condictivity. Thus they can't both be too large,

Point two:
No mention is made of what form of carbon is being discussed. e.g. Graphite and diamond have very different electrical characteristics.

Point three:
The links in my previous post show that diamond semiconductors can offer extremely high performance. Thus any claim that carbon cannot be used as a semicondutor is obviously nonsense.

Once physical phenomenon involved is the semiconductivity due to crystals doping on 4-valence elements, it was presumed the comparision would be done to carbon on diamond structure.

However, was notable the insight that due to carbon electrons be closer to nucleon, the potential energy required to remove it is higher than compared on Silicon or Germanium :





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andre_teprom said:

However, was notable the insight that due to carbon electrons be closer to nucleon, the potential energy required to remove it is higher than compared on Silicon or Germanium :

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Yes, good point.

Another promising way to utilize carbon for semiconductor devices is carbon nanotubes.

I think it's speculative to predict future potential of carbon semiconductor devices from present knowledge and particularly to hold known disadvantages against it as long they don't involve a principle limitation.