Low single charge carrier density materials?

Click For Summary
SUMMARY

This discussion focuses on identifying materials with a single dominant charge carrier and extremely low carrier densities, specifically around 1015 cm-3. The participants highlight that while metals and extrinsically doped semiconductors typically have much higher carrier densities, silicon (Si) can achieve this level at elevated temperatures. At 700K, the intrinsic concentration of Si is approximately 1016 cm-3, necessitating the exploration of wider band-gap materials like silicon carbide (SiC) and diamond for high-temperature applications.

PREREQUISITES
  • Understanding of semiconductor physics, particularly charge carrier densities.
  • Familiarity with intrinsic and extrinsic doping in semiconductors.
  • Knowledge of temperature effects on semiconductor properties.
  • Basic concepts of band gap and its relevance to material selection.
NEXT STEPS
  • Research the properties and applications of silicon carbide (SiC) as a high-temperature semiconductor.
  • Explore the characteristics and potential of diamond as a semiconductor material.
  • Investigate the theory of intrinsic charge carrier densities in semiconductors, especially oxides.
  • Examine data compilations for charge carrier densities at elevated temperatures.
USEFUL FOR

Materials scientists, semiconductor engineers, and researchers focused on high-temperature applications and low charge carrier density materials will benefit from this discussion.

uby
Messages
172
Reaction score
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
 
Engineering news on Phys.org
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.
 
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)?
 
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.
 
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:
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.
 

Similar threads

Diffusion current and carrier concentration equilibrium (unbiased)
  • · Replies 1 ·
Replies
1
Views
2K
High School Thought Experiment on Charge Carriers and Electrical Conduction
  • · Replies 3 ·
Replies
3
Views
562
Undergrad How are holes charge carriers?
  • · Replies 1 ·
Replies
1
Views
1K
Graduate What Happens When Semiconductor Intrinsic Carrier Density Exceeds 10^15 cm^-3?
  • · Replies 6 ·
Replies
6
Views
3K
Semiconductors - Carrier Recombination
  • · Replies 1 ·
Replies
1
Views
2K
Is my calculation of carrier density sufficient for all electrons in bulk?
  • · Replies 1 ·
Replies
1
Views
2K
Graduate Do charge carriers affect the total charge of a material in solid state physics?
  • · Replies 14 ·
Replies
14
Views
4K
Undergrad Minority charge carriers - what are these?
  • · Replies 2 ·
Replies
2
Views
3K
Graduate What can the Fermi surface tell us about a material's properties?
  • · Replies 3 ·
Replies
3
Views
4K
Electron and hole concentration
  • · Replies 1 ·
Replies
1
Views
2K