Low single charge carrier density materials?

In summary, the conversation discusses the search for materials with a single dominant charge carrier and extremely low concentrations (on the order of 10^15 cm^-3). The participants mention that metals and extrinsically doped semiconductors have higher carrier densities, while intrinsic semiconductors and polymers may not be suitable for the application. They also discuss the possibility of modifying the band structure through external means. One participant suggests using Si at elevated temperatures, while another mentions SiC and diamond as potential high temperature semiconductors.
  • #1
uby
176
0
Hello all,

I am trying to identify materials having a single dominant charge carrier having extremely low (on the order of 10^15 cm^-3) concentrations. Metals and extrinsically doped semiconductors, while both possessing a single dominant charge carrier (electrons or holes), tend to have carrier densities on the order of 10^23 cm^-3, which is about 8 orders of magnitude greater than I desire.

[Intrinsic semiconductors are unsuited for my application, since the concentration of electrons and holes are by definition equal (I need a single charge carrier to be dominant). Polymers are probably unsuited for my application as well, which will be above 400C.]

Are there any resources out there with data compilations for charge carrier densities at elevated temperatures?

Also, if there isn't any material that possesses such a low charge carrier density, is it possible to modify the band structure by application of a bias voltage or some other external means?

Thanks,
--uby
 
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  • #2
10^15 cm^-3 is no problems at all for Si. The intrinsic concentration for Si is about 10^10 cm^-3 at 300k so 10^15 (either p or n) is pretty much a mid range doping level. Levels lower than this are commonly used in higher voltage Si devices.
 
  • #3
uart said:
10^15 cm^-3 is no problems at all for Si. The intrinsic concentration for Si is about 10^10 cm^-3 at 300k so 10^15 (either p or n) is pretty much a mid range doping level. Levels lower than this are commonly used in higher voltage Si devices.

Thanks uart, I was unaware of this. My application will probably be around 700K or so, and I'm unsure what the intrinic concentration becomes at such an elevated temperature, but I will direct some effort into finding some Si data.

Do you happen to know of any resources that speak towards the theory of intrinsic charge carrier densities for semiconductors (especially oxides)?
 
  • #4
uby said:
Thanks uart, I was unaware of this. My application will probably be around 700K or so, and I'm unsure what the intrinic concentration becomes at such an elevated temperature, but I will direct some effort into finding some Si data.

Do you happen to know of any resources that speak towards the theory of intrinsic charge carrier densities for semiconductors (especially oxides)?

Yeah the intrinsic concentration is a very strong function of temperature. I've got a graph here that indicates around 10^16 for Si at 700k, so it looks like you'd need to use a wider band-gap material. I don't know a great deal about the properties of semiconductors other than Si so maybe someone else might chime in with some good suggestions. I know that there are definitely other semiconductors available with wider band-gap, but I don't know much about their commercial availability.
 
  • #5
Looking at the following table, semiconductors with a band gap of around 2 eV or more would probably be suitable for your application (Ni much less than 10^15 cm^-3 @ 700k).

http://en.wikipedia.org/wiki/Band_gap
 
Last edited:
  • #6
This is why SiC and Diamond are seen as natural high temperature semiconductors.

Cree has commercialize the former fairly well. I don't know of anyone who's tackled diamond yet commercially.
 

Related to Low single charge carrier density materials?

1. What are low single charge carrier density materials?

Low single charge carrier density materials are materials that have a low concentration of free moving charge carriers, such as electrons or holes. This means that they have a low electrical conductivity and are not good conductors of electricity.

2. What are some examples of low single charge carrier density materials?

Examples of low single charge carrier density materials include semiconductors such as silicon, germanium, and gallium arsenide, as well as insulators like glass and ceramics.

3. What are the properties of low single charge carrier density materials?

Low single charge carrier density materials have a wide band gap, which means a large amount of energy is required for electrons to move from the valence band to the conduction band. They also have low electrical and thermal conductivity, and are resistant to high temperatures and chemical corrosion.

4. What are the applications of low single charge carrier density materials?

Low single charge carrier density materials are used in various electronic devices, such as transistors and solar cells. They are also used in the production of optical fibers, microwave components, and high-temperature sensors.

5. How are low single charge carrier density materials manufactured?

Low single charge carrier density materials are typically manufactured through processes such as crystal growth, vapor deposition, or epitaxial growth. These methods involve controlling the arrangement of atoms to create a material with the desired properties and charge carrier density.

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