Electron-Hole Concentration vs. Carrier Density

[atomicpedals]

I'm a bit unclear on terminology with semiconductors: is there a difference between the "intrinsic carrier density" and the "electron concentration" or "hole concentration"?

 

[gomboc]

The intrinsic carrier density is usually used in relation to intrinsic semiconductiors; materials that have not been 'doped. It is due PURELY to the thermal excitations of electron-hole pairs in the material.

On the other hand the electron concentration and hole concentration are usually calculated for extrinsic semiconductors; materials that have been 'doped'. This is because in doped semiconductors, the electron concentration and hole concentration are not necessarily equal, as they are with intrinsic semiconductors. When you dope a semiconductor like silicon, you add additional donor or acceptor ions which put additional electrons into the conduction band, or holes into the valence band, respectively. The only difference is that the when a donor ion is ionized, the hole created is not in the valence band, and when an acceptor ion is ionized, the electron freed is not in the conduction band.

It's hard to explain without a band diagram, but I hope that helped.