# Resistivity Ratios

1. Jul 30, 2008

### beesher

1. The problem statement, all variables and given/known data

(a) A sample of n-type Germanium contains 1023 ionized donors per cubic meter. Estimate the ratio at room temperature (300K) of the resistivity of this material to that of high purity intrinsic Germanium. The Electron hole product for Germanium is 1038m-6 and it can be assumed that the mobility of the electrons and the mobility of the electrons in the hole are similiar at 300K.

(b) Suppose it takes an energy of 2eV to create a vacany in a certain solid. Show that the relative density of the vacanies of the atoms will always be less than 10-8 per cent unless the melting point is higher than 1000K.

3. The attempt at a solution

Well, I thought since the electron hole product is 1038 then that gives:

Intrinsic - Ne=Nn = 1019
Extrinsic - Ne=1023 therefor Nn=1015

relitive resistivity can be given as PExtrinsic/PIntrinsic.

I'm not really sure how I continue from there. Do I disregard the mobilities because the are similiar?

(b) I'm really unsure how to complete (b), I think it might be something to do with manipulation of n=Ne-E/kT.

Any help would be much appreciated

Last edited: Jul 30, 2008
2. Aug 5, 2008

anyone?