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Homework Help: Current Limitation in a PN junction

  1. Sep 27, 2010 #1
    1. The problem statement, all variables and given/known data

    Describe the limiting physical mechanism for current flow in a p-n junction where there is negligible recombination in the space charge region. Write the equations that describe this current flow process. Define all parameters.

    a) for the general case where the junction is forward biased.
    b) under reverse bias.
    c) describe the total current in (a) and (b) if there is recombination in the space charge region.

    2. Relevant equations

    eqpnc9.gif

    3. The attempt at a solution

    The expression with the defined reverse saturation current comes from the diffusion current densities at the depletion region endpoints, and the recombination will account for a term that depends on the lifetime of going through the depletion region:
    eqpnc10.gif

    Diffusion current is dominant in front bias and current is 'limited' by diffusion of minority carriers, and drift current is dominant in reverse bias and apparently is also 'limited' by the majority carriers.

    I'm not sure what is meant by 'limiting' here?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
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