What Causes Electric Field Breakdown in P-N Diodes?

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In summary, the conversation discusses the concept of reverse biasing in p-n diodes, how breakdown voltage is reached and the role of the electric field in this process. It also touches on rectified AC and the difference between half-wave and full-wave rectifiers. The conversation ends with a discussion on the concentration of holes and electrons in p-n diodes, which is determined by doping.
  • #1
quietrain
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i am not sure if this is considered electrodynamics under classical forum but oh well, here goes

i was reading wiki about p-n diodes and its that for reverse bias diode, because of the anode attracting the holes WITH the cathode attracting the electrons, the depletion zone widens and causes an increase in voltage barrier, so current will be harder to flow.

so when breakdown voltage is reached, the electric field due to the depletion zone breaks down and current flows. so what exactly does the electric field breakdown means?

also regarding rectified ac, i realize that when i rectify an AC source half or full wave, it seems that the oscilloscope shows

ac.png


with the blue part rectified wave, and red the ac transformer source.

so why issnt the blue part directly fitting the red curve? i have to adjust the position of the blue curve upwards on the oscilloscope to fit nicely.

also when full wave rectifying, what gives the extra rectified upward curve? is it the diode causing the original downward ac curve to flip up?

thanks loads sry for the long question
 
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  • #2
in reverse biasing when we apply high reverse voltage then ,electron in the diode bonded by covalent bond gets free due to the brockage of covalent bond & breakdown ocures.the covalent bond are broke up due to the high electric field across the junction,the break down voltage depend on the doping of the semiconducter...
 
  • #3
nikhil khatri said:
in reverse biasing when we apply high reverse voltage then ,electron in the diode bonded by covalent bond gets free due to the brockage of covalent bond & breakdown ocures.the covalent bond are broke up due to the high electric field across the junction,the break down voltage depend on the doping of the semiconducter...

why does having the covalent bond breaking up allows for electricity to pass through?

does covalent bonding has anything to do with the holes and electrons in the p-n semiconductor diode?
 
  • #4
quietrain said:
why does having the covalent bond breaking up allows for electricity to pass through?

does covalent bonding has anything to do with the holes and electrons in the p-n semiconductor diode?

yes ,when covalent bond breaks then electron leave its place from the bond & thus creat a hole there in this manner when one bond break up then a pair of hole& electron is generated.
 
  • #5
quietrain said:
so when breakdown voltage is reached, the electric field due to the depletion zone breaks down and current flows. so what exactly does the electric field breakdown means?

Breakdown can occur through various processes, but generally carriers are generated by impact ionization (avalanche breakdown), or because they can tunnel through the junction (like in a Zener diode). You can check these terms on wikipedia or google for more details.

so why issnt the blue part directly fitting the red curve? i have to adjust the position of the blue curve upwards on the oscilloscope to fit nicely.

Is your oscilloscope in AC mode by any chance? In AC mode, the oscilloscope will remove the DC component, so the rectified wave is "centered". If you set it to DC mode, the curves should match up.

also when full wave rectifying, what gives the extra rectified upward curve? is it the diode causing the original downward ac curve to flip up?
Yes, sort of. In the half-wave rectifier, the diode stops the current one way. In the full-wave rectifier, there's always a diode that let's the current through.
 
  • #6
nikhil khatri said:
yes ,when covalent bond breaks then electron leave its place from the bond & thus creat a hole there in this manner when one bond break up then a pair of hole& electron is generated.

so why does the p-n diode already has a high concentrations of holes at one side and another set of high concentration of electrons at another side as explained in wikipedia?

is it due to doping?
 
  • #7
caffenta said:
Breakdown can occur through various processes, but generally carriers are generated by impact ionization (avalanche breakdown), or because they can tunnel through the junction (like in a Zener diode). You can check these terms on wikipedia or google for more details.



Is your oscilloscope in AC mode by any chance? In AC mode, the oscilloscope will remove the DC component, so the rectified wave is "centered". If you set it to DC mode, the curves should match up.


Yes, sort of. In the half-wave rectifier, the diode stops the current one way. In the full-wave rectifier, there's always a diode that let's the current through.

ah isee thanks!
 
  • #8
quietrain said:
so why does the p-n diode already has a high concentrations of holes at one side and another set of high concentration of electrons at another side as explained in wikipedia?

is it due to doping?

yes it depend on doping that which region will contain holes & which will contain electron ...
 
  • #9
nikhil khatri said:
yes it depend on doping that which region will contain holes & which will contain electron ...

ah i see thank you!
 

What is a P-N diode?

A P-N diode is a semiconductor device that consists of a p-type and n-type semiconductor material sandwiched together. This creates a junction between the two materials that allows for the flow of current in one direction.

How does a P-N diode rectify AC current?

A P-N diode is able to rectify AC current by using its properties of allowing current to flow in one direction only. The diode is placed in series with the AC source, and when the current is positive, it can flow through the diode to the load. When the current is negative, the diode blocks it, effectively converting the AC current into DC current.

What is the difference between half-wave and full-wave rectification?

Half-wave rectification is when only one half of the AC input signal is converted into DC. This is done by using a single diode in series with the AC source. Full-wave rectification, on the other hand, uses a bridge rectifier circuit which utilizes four diodes to convert both halves of the AC input signal into DC.

What are the applications of P-N diodes/rectified AC?

P-N diodes and rectified AC have many applications in electronic circuits. Some common uses include power supplies, voltage regulators, and signal rectification. They are also used in various electronic devices such as radios, televisions, and computers.

What are the limitations of P-N diodes/rectified AC?

One limitation of P-N diodes is their forward voltage drop, which can cause power losses. In addition, they have a limited reverse breakdown voltage, which can damage the diode if exceeded. As for rectified AC, it can produce ripple in the output signal, which may require additional filtering to make it suitable for certain applications.

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