Carrier Concentration in a Semiconductor

[fayled]

Suppose I have an n-doped semiconductor and want to measure the electron concentration in the conduction band as a function of temperature.

How would I go about doing this by measuring the Hall coefficient as a function of temperature, given that I don't know the electron and hole mobilities and thus cannot (unless I am wrong here?) assume that the electrons provide the dominant contribution to the Hall coefficient.

If I could assume electrons were the dominant carriers it would be simple since then the Hall coefficient R_H=-1/ne.

 

[espen-4]

If the electron concentration (n) is significantly higher than the hole concentration (p) (say 100 times higher) then you can use the approximation RH=-1/(ne).
To determine whether this approximation is ok to use you must calculate the hole concentration p=ni^2/n. Where ni is the intrinsic carrier concentration. ni is temperature dependant (increases with temperature). It is different for all materials. ni is often tabulated in the scientific literature.
Caution: If you are working with low band gap materials and / or the temperature is high electrons will be excited from the valence band into the conduction band. This also creates holes. In these cases the hole concentration can become comparable to the electron concentration and the above approximations are no longer valid and you must take into account the holes as well.