I was wondering whether there is a difference between Zener effect and avalanche effect? How do they differ?
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\$\begingroup\$ Third result for a google search of "avalanche diode": Zener and Avalanche Breakdown/Diodes \$\endgroup\$– Phil FrostJan 14, 2013 at 14:26
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2 Answers
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There are two entirely different effects exploited in zener diodes; at low voltages, the effect is tunnelling across the junction, and at higher voltages, the effect is identical to the avalanche diode. The temperature coefficient of each effect is different; I can't find my reference offhand but one (I think tunnelling) the zener voltage decreases with temperature and the other effect has an increasing voltage with temperature.
The importance of this detail is that zener diodes around 5.6 or 6.2 volts have close to zero temperature coefficient of voltage, since in that voltage range, both effects are equally important.
Edit : "zener breakdown" at low voltages may not be tunnelling as I (mis?-)remembered; however it is a separate effect from avalanche breakdown. I did get the temperature dependence right way round though.
Wikipedia suggests the difference is this : in the zener effect, the electric field across the junction breaks bonds to release carriers; while in the avalanche effect it is collisions which break bonds and release carriers.
On the other hand, this article does use the words "quantum tunnelling" to describe the Zener effect, so maybe I'm not completely senile yet...
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\$\begingroup\$ Yes - tempco for Zener effect is negative and for avalanche effect it is positive. \$\endgroup\$– LvWSep 29, 2014 at 20:19
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I saw a video about the explanation of the Zener breakdown phenomena. As per that video in zener breakdown due to tunneling the electrons are created. This tunneling phenomenon is due to the presence of a high electric field present between the PN junction and the p/n type semiconductor. As per my understanding, there shouldn't be a high electric field present between the PN junction and the battery as both sides have the same charge polarity and hence less potential difference and eventually less electric field in case of reverse bias.