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Modeling >> Semiconductor Devices >> depletion width
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Message started by Jason_class on Sep 14^th, 2003, 5:22am

Title: depletion width
Post by Jason_class on Sep 14^th, 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

Title: Re: depletion width
Post by Geoffrey_Coram on Sep 16^th, 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.

Title: Re: depletion width
Post by jason_class on Sep 18^th, 2003, 9:05am

Thanks a lot Geoffrey.
You are very helpful

rgds and thanks
Jason