Variation of Potential outside a PN junction

In summary, we are considering a step junction at equilibrium where no external voltage is applied. The potential variation is shown as a negative potential at the P region, which is constant, and increases through the transient region to become positive in the N region. According to the equation for potential, the value at the P region should be positive and higher than the negative potential in the N region. Additionally, the positive potential at the P region should drop to a negative value in the transition region due to the presence of electrons, and slowly increase to become positive as the transient region changes from negative to positive. The graph should then become negative again as the positive region ends, caused by the presence of electrons in the N region. This is due to the fact
  • #1
Amal Thejus
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1

Homework Statement


1. We are considering a step junction at equilibrium(no external voltage applied).

2. The potential variation is shown as negative potential at P region(which is shown as constant) and increasing through the transient region to become positive in the n region.

Homework Equations


Potential V=Q/4ΠΣ

The Attempt at a Solution


1. As per the equation for potential, the value of potential at the P region should be positive(since Q=positive here) and shown at a higher level than the negative potential in the N region(since Q=negative here).

2.Also the positive potential at P region should drop to a negative value in the transition region next to it(because of the presence of electrons there at equilibrium) and slowly increase to become positive potential as the transient region changes from negative to positive. As the positive region comes to an end the graph should again become negative due to the electrons in the N region.
 

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  • #2
A p or n-type semiconductor is neutral. When an n-type piece is in contact with a p-type piece, some of the free carriers migrate to the other side, electrons from the n-type part and holes form the p-type part. These holes make the region near the pn junction positive, and the electron, having diffused to the p-type side, make a negative region near the junction.
 
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  • #3
ehild said:
A p or n-type semiconductor is neutral. When an n-type piece is in contact with a p-type piece, some of the free carriers migrate to the other side, electrons from the n-type part and holes form the p-type part. These holes make the region near the pn junction positive, and the electron, having diffused to the p-type side, make a negative region near the junction.

Thank you so much. That was kind of a stupid question right. I can't believe I missed the material being neutral. Thanks again.
 

Related to Variation of Potential outside a PN junction

1. What is a PN junction?

A PN junction is a boundary between two types of semiconductors, one with an excess of positive charge carriers (p-type) and the other with an excess of negative charge carriers (n-type). This junction allows for the flow of electric current in only one direction, making it a key component in many electronic devices.

2. How does the potential vary outside a PN junction?

The potential outside a PN junction varies due to the difference in charge carrier concentrations between the p-type and n-type materials. This creates a built-in electric field that causes a potential drop across the junction, with the positive side being on the p-type side and the negative side on the n-type side.

3. What factors affect the variation of potential outside a PN junction?

The main factors that affect the variation of potential outside a PN junction are the doping concentrations of the p-type and n-type materials, the width of the depletion region, and the applied bias voltage. Higher doping concentrations and wider depletion regions result in a larger potential drop across the junction, while an applied bias voltage can either increase or decrease the potential depending on its polarity.

4. How does the variation of potential outside a PN junction affect device performance?

The variation of potential outside a PN junction is crucial for the proper functioning of electronic devices. It allows for the flow of current in one direction, making it possible to create diodes and transistors. It also affects the speed and efficiency of the device, as a larger potential drop means a stronger electric field and faster movement of charge carriers.

5. Can the potential variation outside a PN junction be controlled?

Yes, the potential variation outside a PN junction can be controlled through the process of doping, where impurities are intentionally added to the semiconductor material to alter its electrical properties. By adjusting the doping concentrations and the width of the depletion region, the potential drop across the junction can be manipulated, allowing for customized device performance.

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