Help with the Key Points of Zener Breakdown and Avalanche Breakdown

AI Thread Summary
Zener breakdown occurs when the electric field in a diode exceeds a critical value, causing electrons to be pulled from the lattice and resulting in a rapid increase in current. In contrast, avalanche breakdown involves high-velocity minority carriers that generate additional charge carriers, leading to an explosive current rise. Doping is crucial as it influences the breakdown voltage and the diode's ability to handle reverse bias without damage. The temperature coefficients for Zener and avalanche effects differ, with Zener effects exhibiting a negative temperature coefficient for voltages below 5.6 volts and avalanche effects showing a positive coefficient above that threshold. Understanding these mechanisms is essential for effectively utilizing Zener and avalanche diodes in electronic applications.
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The avalanche breakdown occurs because of the ionisation of electrons and hole pairs whereas the Zener breakdown occurs because of heavy doping. The Zener and the avalanche effect may occur simultaneously or independently of one another in PN junction. What the key points of them?
Good day, all
I am familiar with both of terms that I speak of in title. But I cannot find a full answer, so I might as well ask the PhD'ers here. What is really happening in Zener and Avalanche breakdown? I have read Guide to Zener Effect and Avalanche Effect and still feel confused.
And yes I get that impact ionization thing etc. But still, how does Zener differ from Avalanche breakdown? Why is doping so important? How come it doesn't damage the diode? Why is current constant? Why would it be constant when u exceeded the depletion zone(reverse bias), current should be proportional to voltage? (more voltage, more energy, more charges pulled out, more current) I am trying to get a full picture here. You may post something with detailed quantum mechanics, semiconductor theory.

Thank you in advance. :smile:
 
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1.) Z (Zener) diode:
When the field strength exceeds the critical value of about 1E5 V/cm, the field forces are so strong that the electrons are torn out of the lattice. This causes the current to rise explosively.

2.) Avalanche diode:
At very high velocities of the minorities, there is a secondary effect where more charged carriers are torn out of the lattice - and the current rises explosively (like an avalanche)

3.) It is important that the temperature dependencies of both effects have different signs: The tempco is negative for Zener effects (Vz<5.6 volts) and positive for avalanche effects (Vz>5.6 volts).
At a Z-voltage of about Vz=5.6 volts, both temperature effects almost compensate each other.
 
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