Hey all!

I have the following question:

A sample of silicon is doped with arsenic such that the concentration of free electrons is 2.3*10^15 cm-3 when the temperature is 311 K. Determine the concentration of holes in the sample at that temperature.

Now from what I know, this is an Extrinsic semiconductor. But I am having trouble finding the equation to use for this one. I would not use this correct:

ni = BT^(3/2)*e(-Eg/2KT)

If not Im stuck on the path im supposed to take. If anyone could lead me down the correct road itd be much appreciated!

 

You have the intrinsic concentration, now use the mass action law: http://en.m.wikipedia.org/wiki/Mass_action_law_(electronics)

 

Thank you for the quick reply! But why is this an intrinsic instead of an Extrinsic? Is it because it is not from group 3 or 5?

 

It is an extrinsic semiconductor, you've added a dopant, but the mass action law relates the intrinsic carriers to an extrinsic (actually both), at thermal equilibrium.