Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Difution drift currect question

  1. May 21, 2010 #1
    [tex]J_e=q\mu \bar{n}E-qD_e\frac{d\bar{n}}{dx}[/tex]
    i cant understand this equation
    what each member of this equation

    i only know that [tex]\mu[/tex] is the drift coefficient
    E is the field

    what the rest of the memebers represent
  2. jcsd
  3. May 21, 2010 #2


    User Avatar

    Staff: Mentor

    I googled diffusion drift current, and got lots of good hits. Here's one that should answer your question:


  4. May 22, 2010 #3
    n is the electron density what is the meening of

    in this page it doesnt say what is D_e

    the is also a formula for hole current
    why it has plus in the middle (in the electron current we have minus in the meedle)
  5. May 22, 2010 #4
    dn/dx would be the derivative of electron density with respect to the coordinate x. In other words, if you're simply dealing with a semiconductor in which the elctron density only changes in x (i.e. y, and z components are constant), there will be a diffusion current where electrons will diffuse from a higher concentration area to a lower concentration area. This is mathematically depicted by 'dn/dx'.

    D_e (or D_n) is the diffusion coefficient of electrons. It depends on the mobility of the electrons, and temperature of the sample.

    The hole current has a plus because holes are positively charged as opposed to electrons which are negatively charged
  6. May 22, 2010 #5
    thanks :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook