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pyctz
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why do electric field is zero out side of depletion region?
can you explain it with using of coulomb rule?mfb said:In an area with charge carriers, how could there be a permanent electric field without current flow?
in depletion layer there are uncovered charges that generate electric field , how cancel their field?mfb said:This is simple U=RI with negligible I and finite R. The Coulomb rule is not useful here.
the remaining atom don't generate any fied, then who cancel the field of depletion layer?mfb said:The remaining atoms have a charge as well. There is nothing "uncovered". A doped semiconductor has free charges of one type with zero overall charge density. If you remove those free charges the volume gets charged.
Sure they do.pyctz said:the remaining atom don't generate any fied
if for each atom the overall charge is zero, then they don't generate any fied.mfb said:Sure they do.
Replace a silicon atom with boron. It has one electron and one proton less, so the overall charge is zero .
but who cancel the field of depletion layer?mfb said:And that's exactly what you have outside the depletion region.
it is not correct,mfb said:The other half of the depletion layer.
sheets of uniform charge must have infinite dimension(infinite plane) to lead uniform fieldsmfb said:Distance does not matter in a one-dimensional problem. Sheets of uniform charge density lead to uniform fields in all space (outside those sheets).
i don't talk about approximationmfb said:Compare the typical thickness of a depletion region with the typical dimension of a semiconductor device.
The infinite sheet is a good approximation unless you consider modern microprocessors, and then things are much more complicated anyway.
actually, in non ideal diode electric field is zero outside of depletion region.mfb said:Your statement in post 1 is an approximation.
Actually, every description you will ever see is an approximation. Just the quality is different.
inside a conductor The electric field is exactly zeromfb said:- The electric field is never exactly zero anywhere.
- Charge distribution is never exactly uniform in space
- the depletion layer does not have an exact boundary
- ...
All approximations.
if The electric field is not zero the free charges move until it becomes zeromfb said:Not exactly.
As I said, those statements are all approximations.
In the real world, physics is never exact.
if The electric field is not zero the free charges move until it becomes zeromfb said:Not exactly.
As I said, those statements are all approximations.
In the real world, physics is never exact.
The electric field is zero outside of the depletion region due to the balance between the built-in potential and the potential created by the majority carriers in the region. This results in a net charge of zero and therefore, no electric field.
No, there is still an electric field present due to the presence of minority carriers and surface charges on the edges of the depletion region. However, this field is small and can be considered negligible compared to the electric field within the depletion region.
The width of the depletion region directly affects the strength of the electric field outside of it. A wider depletion region results in a stronger electric field, while a narrower depletion region results in a weaker electric field outside of it.
Yes, under certain conditions such as high voltage or temperature, the depletion region can expand and the electric field may extend beyond its boundaries. Therefore, the electric field outside of the depletion region is not always zero.
The electric field outside of the depletion region is a result of the potential barrier created by the difference in the Fermi levels between the p-type and n-type materials. The potential barrier prevents the majority carriers from crossing the junction and creates a net charge of zero outside of the depletion region.