Welcome to the P-n Junction Inquiry

In summary, the conversation is about a question regarding the behavior of the electric field in a p-n junction, specifically in figure B of the Wikipedia article. The speaker believes the figure is incorrect and explains their reasoning. The other person disagrees and explains that the figure is a simplified representation and that the depletion region is not infinite in extent. They also clarify that the field is constant outside the regions with net charge. The conversation highlights the complexity of the topic and the need for approximations in understanding it.
  • #1
daudaudaudau
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 ??
 
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  • #2
The figure looks good.
daudaudaudau said:
It is going to be positive outside the depletion region
No.
(explain more what you don't understand to get more specific answers)
 
  • #3
mfb said:
The figure looks good.
No.
(explain more what you don't understand to get more specific answers)

Well the depletion region is a dipole, isn't it? So the e-field will look like this

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/imgele/edip2.gif

So if the field is negative "inside" the dipole, it is positive outside (but of small magnitude, of course).
 
  • #5
mfb said:
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
daudaudaudau said:
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.
 

FAQ: Welcome to the P-n Junction Inquiry

1. What is a P-n Junction?

A P-n junction is a boundary or interface between two different types of semiconductor materials, P-type and N-type. It is a fundamental building block in electronic devices such as diodes, transistors, and solar cells.

2. How does a P-n Junction work?

A P-n junction works by creating a depletion region, which is an area with no free charge carriers, at the interface between the P-type and N-type materials. This results in a built-in electric field that allows for the flow of current in one direction, making it useful in electronic devices for rectification, amplification, and switching.

3. What is the difference between a P-n Junction and a Schottky Barrier?

A P-n junction is formed by the interface of two different types of semiconductor materials, while a Schottky barrier is formed by the interface of a metal and a semiconductor. A P-n junction allows for the flow of current in one direction, while a Schottky barrier allows for the flow of current in both directions.

4. What are some applications of P-n Junctions?

P-n junctions have a wide range of applications in electronic devices. They are commonly used in diodes, transistors, and solar cells. They can also be used in sensors, integrated circuits, and optoelectronic devices such as LEDs and photodetectors.

5. How are P-n Junctions created?

P-n junctions can be created through a process called doping, where impurities are intentionally added to a semiconductor material to change its electrical properties. P-type materials are doped with acceptor atoms, while N-type materials are doped with donor atoms. When these materials are brought together, a P-n junction is formed at the interface.

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