PN-junction breakdown

  • Thread starter abrowaqas
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Main Question or Discussion Point

Why there is sudden increase in the small reverse saturation current at the breakdown voltage in PN-junction Diode?
 

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  • #2
marcusl
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The phenomenon is called "breakdown" because the junction is literally broken. A typical failure mechanism when the applied voltage gets too big is equivalent to an arc through the junction, resulting in localized crystal melting. This in turn puts a low resistance "short" in parallel with the junction, giving rise to large current flow.
 
  • #3
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The phenomenon is called "breakdown" because the junction is literally broken. A typical failure mechanism when the applied voltage gets too big is equivalent to an arc through the junction, resulting in localized crystal melting. This in turn puts a low resistance "short" in parallel with the junction, giving rise to large current flow.
Although breakdown can cause irreversible damage to a junction, that's not the cause but a possible effect of the high current.

Generally, breakdown occurs when a large number of carriers are generated very quickly, via impact ionization for example, or when carriers can tunnel across the junction through the bandgap.
 

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