Diode operation from reverse bias to zero bias

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Discussion Overview

The discussion revolves around the operation of a diode transitioning from reverse bias to zero bias, focusing on the behavior of the depletion region and the nature of covalent bonds in semiconductor materials. Participants explore the mechanisms behind the return to zero bias and the implications of charge carrier behavior in the context of silicon's crystalline structure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why a diode returns to its zero bias state after being reverse biased, suggesting that the uniformity of silicon's lattice and the bonding of electrons may prevent this return.
  • Another participant explains that the depletion region's width can change with applied voltage, emphasizing that the crystalline structure remains intact while charge displacement occurs.
  • A participant expresses curiosity about how covalent bonds between silicon and boron can be broken to allow the diode to return to an unbiased state.
  • There is a discussion about the nature of covalent bonds, with one participant affirming that these bonds involve sharing electrons.
  • Another participant raises the question of how charge carriers can become free again once covalent bonds are formed.
  • One participant introduces the idea that semiconductor crystals possess unique properties that allow 'trapped' electrons and holes to remain mobile under an external electric field.
  • A later reply suggests that leakage current may contribute to the discharging process, attributing it to charge carrier drift influenced by the electric field.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the behavior of charge carriers and the nature of covalent bonds in semiconductors, indicating that multiple competing views remain without a clear consensus on the mechanisms involved.

Contextual Notes

Limitations include potential misunderstandings about the nature of covalent bonds and the specific conditions under which charge carriers behave as they do in semiconductor materials. The discussion does not resolve these complexities.

CaptainMarvel1899
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Assume we have a closed diode circuit .We connect the n type region of the diode to the positive terminal of the battery.We connect the p type region of the diode to the negative terminal of the battery.The depletion layer is increased.Now we open the circuit.Why the diode returns to its zero bias mode ?The lattice of silicon is more uniform and electrons have created bonds with unpaired electrons from Si atoms so they could not "return". What am I missing?
 
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The depletion region is where charge is concentrated and it can increase or decrease in width depending on the applied voltage. The crystalline material atoms don't get displaced; just the charge gets displaced.
 
dlgoff said:
The depletion region is where charge is concentrated and it can increase or decrease in width depending on the applied voltage. The crystalline material atoms don't get displaced; just the charge gets displaced.
Hmm I know that .I was just wondering how the covalent bonds between Si and B- can be broken so the diode would return to its unbiased state.
 
Isn't a covalent bond one where there's a sharing of an electrons? Same answer as before.
 
Yes it is.
 
Once they form the covalent bond , how can they be free charge carriers again?
 
CaptainMarvel1899 said:
What am I missing?
This part
Semiconductor crystals has something special between the 'pure' covalent bonds and metalic bonding. That's what makes them special. So the 'trapped' electrons/holes in the enlarged depletion layer are still mobile, their state is forcibly maintained just by the appropriate external electric field.
 
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CaptainMarvel1899 said:
Assume we have a closed diode circuit .We connect the n type region of the diode to the positive terminal of the battery.We connect the p type region of the diode to the negative terminal of the battery.The depletion layer is increased.Now we open the circuit.Why the diode returns to its zero bias mode ?The lattice of silicon is more uniform and electrons have created bonds with unpaired electrons from Si atoms so they could not "return". What am I missing?

Leakage current does the discharging? Technically this is charge carrier drift due to the now comparatively large electric field.
 

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