# Homework Help: Electron drift question

1. Oct 18, 2015

### orangeincup

1. The problem statement, all variables and given/known data
A sample of Si, in which 0<=x<=(25*10^-4), electron concentration is n(x)=5*10^16 cm^-3) * exp(-x^3/2*10^-8), temperature is 300k and electron mobility is 1300 cm^2/V*s. The electron current through the Si has both drift and diffusion components and total electron current density through the sample is independent of x.

Find an expression for the electric field as a function of electron current density.
Evaluate the electric field at 10*10^-4 if the electron current density is 15 A/cm^2.
Evaluate the electric field at 10*10^-4 if the electron current density is 0 A/cm^2.

2. Relevant equations
Jn=e*n(x)*un*Ex+e*Dn*du/dx
Jn=pvd
Jn=(ep)vdp

3. The attempt at a solution
For the first part, I think I know how to solve if I can calculate Jn, since I have all the other values except Jn and Ex(which I need to solve for). Is there an equation which lets me solve for Jn with the values I have? Is there a constant I'm missing?

2. Oct 23, 2015

### Staff: Admin

Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?

3. Oct 24, 2015

### orangeincup

Yeah I solved it, thanks

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