# extend the conductivity expression in terms of mobility and explain how carrier concentration and mobility vary with respect to temperature?plz reply someone as soon as possible.....thanku.....

Yash Jain
55 Points
8 years ago
I suppose this question is from Semiconductors
See, for that we have ITotal = Ie + Ih
If { V is the potential difference across the semiconductor,
R is the resistance through the semiconductor,
e is the charge of electron and hole,
Ne and Nh are the respective carrier densities,
A is the area of cross section of the semiconductor,
ve and vh are the drift velocities of electrons and holes respectively }
then, V/R = NeeAve + NheAvh
E.l / pl/A = eA.(Neve + Nhvh)
therefore, 1/p = e(N
eve/E + Nhvh/E)
or 1/p = S = e(Neue + Nhuh)
where p is the resistivity, S is conductivity and ue,uh are respective mobilities.
As the temperature increases, the mobility of the carriers decrease upto certain extend but there is large increment in their concentrations. So there is a considerable increase in the conductivity of semiconductors wrt the conductivity expression.
Hope that’ll help.