Why charges travel faster in semiconductor than in metallic conductor?

[memilyc]

Homework Statement

"Use the equation I=nAve to justify why charges travel faster in semiconductor than in metallic conductor. Assume that the dimensions and current are the same. "

Homework Equations

I=nAve
I know I = current, n = number density, A= cross sectional area v= drift velocity and e = charge of electrons

The Attempt at a Solution

Is metallic conductor denser than semiconductor, hence the drift velocity is lower? Thanks in advance.

 

[Simon Bridge]

Relationship of drift velocity to charge density:
http://en.wikipedia.org/wiki/Drift_velocity
http://ecee.colorado.edu/~bart/book/book/chapter2/ch2_6.htm

 

[Capt.Ali]

Thanks a lot.