P-n junction

  • #1
302
0
Hello.

I have a question regarding the p-n junction. When I look at figure B here:

http://en.wikipedia.org/wiki/P-n_junction

it looks completely wrong to me. Take the E-field. It is going to be positive outside the depletion region, which in turn will make the voltage tend towards zero for x→±∞. Right ??
 

Answers and Replies

  • #2
34,946
11,127
The figure looks good.
It is going to be positive outside the depletion region
No.
(explain more what you don't understand to get more specific answers)
 
  • #5
302
0
It is not, you have two "infinite" sheets, and infinite sheets have a constant field around them - two sheets with opposite charge of the same magnitude lead to fields that cancel everywhere outside.
Well, clearly the depletion region is not infinite in extent. Also, the field is not constant in the figure that you said looks good.
 
  • #6
34,946
11,127
Well, clearly the depletion region is not infinite in extent.
That is a very good approximation for most transistors.
Also, the field is not constant in the figure that you said looks good.
The field is zero outside the regions with net charge, so the potential is constant. The field is not constant in the region with net charge, as there is net charge on the sides.
 

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