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depletion width (Read 4040 times)
Jason_class
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depletion width
Sep 14th, 2003, 5:22am
 
Hello All ,

May I know why the depletion width for n side of a pn junction is longer than that of the p side?
Also why is the p(x) for n side smaller than that of pside?
Kindly let me know which formula I should refer to?
Thank you


rgds and thanks
jason_class
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Geoffrey_Coram
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Re: depletion width
Reply #1 - Sep 16th, 2003, 3:15pm
 
Jason -
If the dopant density (which I think you are calling p(x)) is smaller on the n side, then this forces the depletion width to be larger on the n side.  It's simple math: the depleted charge on either side must be equal (at equilibrium), and the depleted charge is the density times the volume.  Assuming equal cross-sectional area, you're left with the depletion width.

As to why n doping is less than p doping, this is process-specific.  One could build an (n)(p+) diode or an (n+)(p) diode, ie, with either side more highly doped than the other.  I don't know if there's a reason that diodes would typically be doped stronger on the p side.
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jason_class
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Re: depletion width
Reply #2 - Sep 18th, 2003, 9:05am
 
Thanks a lot Geoffrey.
You are very helpful


rgds and thanks
Jason
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