Different model explaining semiconductor

tomz

Hi everyone, I have a question here on what cause doped semiconductors to conduct. (such as Silicon with some As present, this is one atomic number higher)

On my chemistry book, it says As covalently bond with 4 Si atoms as Si does, so the lattice is preserved, and 1 of its valence electron is free (as it have 1 more electron in outer shell), and therefore the material is conductive.

On my physics book, it says the reason is that As atom provide a energy level that is very close to the conductive band of Si lattice, and the original energy difference between conductive and valence band of Si is much larger. So the material is now conductive (thermal energy supplied, electron transit)

My question is, which explanation is correct? Or is it coincident that every doped element provide energy level that close the the existing band so a jump is possible? (because not just As, a lot of element will cause increase conductivity of semiconductor)

thanks

ZapperZ

They are the same explanation.

When you doped with the As atom, one of its valence electron is rather loosely bound to the atom. The thermal energy is sufficient to delocalize that electron.

And if you translate that situation in terms of the band diagram, that is what you get from your physics text. They are both describing the same, identical situation, to varying degree of exactness. The band diagram, if one can drive it, is the more exact description.

Zz.

tomz

Thank you!