Basic semiconductor theory.

Discussion in 'Homework Help' started by Urmi, Jul 31, 2010.

  1. Urmi

    Thread Starter New Member

    Jun 5, 2010
    3
    0
    Hi everyone,I desperately need to understand a few concepts regarding semiconductors and how they basically work(referring to a p-n junction diode)..please answer my 4 questions...

    1. What is it that actually stops the diffusion of carriers at the end of depletion layer formation?...is it that the stationary charges(e.g negative ions on the p-side) on either side repel the incoming charges?

    2.When we say that in reverse bias,the holes in the P-side are attracted to the negative terminal (of the battery) at the P-side,we are basically saying that the minority electrons (that reside in the conduction band of the host semiconductor atoms in p-type crystal) move toward the junction...so it's exactly analogous to when the electrons from the n-side move in during depletion layer formation..is that right?

    3.In forward bias, electrons and holes from close to the junction migrate a short distance and recombine. Since this continually happens, the external circuit appears like a steady current is flowing(my teacher told this in class)....does this mean that the electrons in the Conduction Band(of the atoms in the p side) move toward the junction?.....

    (there'll also be some of these conduction band electrons that cross over into the n side, in order to fill in the vacancies created by electrons in the n side, which migrate towards the positive terminal,leaving behind holes when the forward bias is applied)

    4.After electron-hole pairs are generated,do the electrons generated accumulate on the p-side...what does happen to them?
     
  2. Fraser_Integration

    Member

    Nov 28, 2009
    142
    5
    1. Yes an in-built electric field opposes the flow of electrons.

    2. Not sure what you're asking

    3. Yes there is a much smaller drift current which acts in the opposite direction to the diffusion current.

    4. This is similar to 1. The electrons at the p-type end of the depletion layer, and the holes at the n-type create the opposing electric field which limits diffusion.
     
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