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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

    berkeman

    User Avatar

    Staff: Mentor

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

    http://ecee.colorado.edu/~bart/book/book/chapter2/ch2_10.htm

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

    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 :)
     
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