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Forward biased PN junction help needed

  • Thread starter CptMad
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Homework Statement



Assume silicon, at room temperature (300k) and complete ionization.
An abrupt n+-p junction with Nd=10^20 cm^-3 and Na=10^17 cm^-3 is forward biased at 0.5V



Homework Equations



a)Draw the band diagram, label n and p regions, show direction of the current flow. Also what is the current type (electrons or holes, drift or diffusion) in the p-type region just outside the depletion region?
b)Calculate the depletion charge capacitance per unit area.

The Attempt at a Solution


I have managed to draw the band diagram but I'd appreciate it if there was a way I could check my answers. Also I get confused with the wording for the 2nd portion of part A. I understand that the current in a forward biased pn junction is due to diffusion would this be considered the same for p-type region?

For part B would it be correct if I use the equation

C'=[(eεsNaNd)/(2(Vbi-Vr)(Na+Nd))]^1/2

But I get stuck since C=AC' but I can't seem to figure out the value for A, would I be able to use A=10^-4cm^2?
 

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