Calc Conductivity of an intrinsic semiconductor

[nanostar]

Calculate the conductivity of an intrinsic semiconductor at room temperature and from the following data:

(n)Carrier density(where electron=holes)=2.9*10^19 carrier/m^3
Electron mobility = 0.45 m^2/V s
Hole Mobility = 0.23 m^2/V s
(q)Charge per electron/hole = 1.6*10^-19 coulomb/carrier

I know that conductivity = nqu

but how do I include the e and h mobility too?

 

[ehild]

What is the conductivity if there are two kinds of charge carriers?

ehild

 

[nanostar]

What is the conductivity if there are two kinds of charge carriers?

ehild

?

 

[ehild]

From Wikipedia:

When there is more than one species (e.g., a plasma with electrons and ions, or a semiconductor with electrons and holes), the total conductivity is
σ = ∑ niμi | qi |
i

where the ith species has number density ni, charge qi, and mobility μi.

ehild

 

[GabbleRatchet]

σ = n_eq_eμ_e+n_hq_hμ_h

Where the subscripts are electron and hole respectively.

You have to account for the fact that the carriers are of opposite charge and travel in opposite directions (I think). If in doubt, you can always ask on Thursday...