Why is there reverse current in diode equation?

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Discussion Overview

The discussion centers around the presence of reverse current in the diode equation, exploring the underlying mechanisms such as drift and diffusion currents, as well as the effects of temperature on leakage currents. The scope includes theoretical aspects of diode operation and the implications of these currents in practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the origin of reverse current in the diode equation, noting that the derivation assumes no drift.
  • Another participant explains that even without bias, there exists a diffusion current due to concentration differences between n-type and p-type materials, which is essential for diode operation.
  • A further contribution discusses the role of the depletion zone in creating drift currents, referencing the photoelectric effect in photodiodes and the application of external reverse bias to enhance current.
  • Multiple participants mention the existence of temperature-dependent leakage currents, suggesting that these currents may also contribute to the reverse current observed in diodes.
  • One participant requests further information or resources regarding temperature-dependent leakage currents, indicating a desire for deeper understanding.
  • Another participant notes that minority carriers are generated through random thermal generation of electron-hole pairs, emphasizing the temperature dependence of this generation rate.

Areas of Agreement / Disagreement

Participants express varying perspectives on the mechanisms behind reverse current, with some agreeing on the role of diffusion currents while others highlight the importance of temperature-dependent effects. The discussion remains unresolved regarding the specific contributions of these factors.

Contextual Notes

The discussion includes assumptions about the behavior of carriers in diodes and the dependence of certain phenomena on temperature, which may not be fully explored or defined within the posts.

Who May Find This Useful

Readers interested in semiconductor physics, diode operation, and the effects of temperature on electronic components may find this discussion relevant.

satominari
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When deriving diode equation, it is assumed that there's no drift.
But still, in the result, we have a reverse current which is a drift...
I don't get where this comes from.
 
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Even when the diode is not biased there is a diffusion current from n-type material to the p-type material because of difference in electron concentrations similar to the hole diffusion current from p-type material to the n-type material. These opposite currents carry like charges accumulating on he edges of the depletion zone while canceling each other within the depletion zone. These diffusion phenomenon is essential for the operational principal of the diods.
 
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Yes. So created depletion zone is responsible for drift currents. Imagine the photoelectric effect for photo diods. Photons falling on the depletion zone of the diods liberate electrons biased by the electric fields already created by the diffusion currents. In a photo diod circuit, an external reverse bias is also applied to increase the photo diot current (signal).
 
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You will most likely have a temperature-dependent leakage current. Also see post #3.
 
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Svein said:
You will most likely have a temperature-dependent leakage current. Also see post #3.

Thanks for the reply. But could you explain or give me a link about temperature dependent leakage current? Thank you so much!
 
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The minority carriers being discussed above are generated by random thermal generation of electron-hole pairs. The generation rate is temperature dependent.
 

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