Calculating Drift Velocity in Pure Silicon: Need Help

[becon]

I have a small question that can't solve.
How long does it take an average electron to drift 1um in pure silicon in an electric field of 10^4 V/m ?

drift velocity v_d = I / (n*q*A)
but don't know how to calculate
can you help me ?
thank you.

 

[ehild]

The drift velocity is mobility times electric field strength.

Google the "mobility of electron in silicon".

ehild