CrazyEngineers Archive
Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@mallumatmari • 12 Mar, 2013
1) why breakdown voltage decreases with increase in doping level, what actually happens when diode is heavily doped. Why zener breakdown is less than avalanche breakdown.
@mallumatmari • 12 Mar, 2013 Let it be guys I got the answer....
@Jeffrey Arulraj • 12 Mar, 2013
mallumatmari
Let it be guys I got the answer....
Can you pls post the answer you got for us to also learn and edify our knowledge
@mallumatmari • 12 Mar, 2013 Zener breakdown:
1)heavily doped therefore have narrow depletion layer
2)strong electric field is developed across this narrow layer.
3)covalent bonds break due to very strong electric field so even a small amount of reverse voltage is capable of producing large number of current carriers.

Therefore zener breakdown voltage is less than avalanche breakdown.
@Jeffrey Arulraj • 12 Mar, 2013 Avalanche Breakdown needs collision of minority carriers and covalent bonds to provide electrons and holes. This needs higher potential cos the minority carriers need to be developed in sufficient numbers to get sufficicent current resulting in break down
@Ankita Katdare • 19 Mar, 2014 A lot of people seem to be looking for this.

I hope this image from Harvard can be of some help -

zener_charac_1
@Void Runner • 03 Apr, 2014 The main difference between the two is that avalanche breakdown is a result of carrier multiplication while Zener effect is a result of electron tunnelling. Both occur in reverse bias, but the Zener diode actually works on the basis of both effects, not one.
@vishnu tej • 28 May, 2015
  • The diode which have lesser doping undergo avalanche breakdown when high reverse voltage is applied. The lesser doping means the depletion width is large and so electric field within depletion region is not so high. Hence the electric field would not be able to pull out electrons from the outer shell of atoms and breakdown doesn’t occur in depletion region. But as the depletion region is large and hence when the minority charge carriers move through the depletion region, they get accelerated by the electric field and that even for larger time (as distance through which acceleration is provided is large). Hence minority charge carriers acquire high velocity and so high kinetic energy. When these charge carriers strike with atoms in the n-type and p-type regions, the high kinetic energy gets converted to thermal energy and hence due to this energy electrons from the outermost shell are pulled out and large current starts flowing. This type of breakdown is called avalanche breakdown.
  • But due to the high thermal energy, the temperature rises and diode gets burned. Due to this reason the simple diodes (where avalanche breakdown occurs) is not used in the applications and instead Zener diode is used in the application circuits of breakdown diodes such as regulating power supply.
@Md Rafiqul Setu • 10 Dec, 2015
vishnu tej
  • The diode which have lesser doping undergo avalanche breakdown when high reverse voltage is applied. The lesser doping means the depletion width is large and so electric field within depletion region is not so high. Hence the electric field would not be able to pull out electrons from the outer shell of atoms and breakdown doesn’t occur in depletion region. But as the depletion region is large and hence when the minority charge carriers move through the depletion region, they get accelerated by the electric field and that even for larger time (as distance through which acceleration is provided is large). Hence minority charge carriers acquire high velocity and so high kinetic energy. When these charge carriers strike with atoms in the n-type and p-type regions, the high kinetic energy gets converted to thermal energy and hence due to this energy electrons from the outermost shell are pulled out and large current starts flowing. This type of breakdown is called avalanche breakdown.
  • But due to the high thermal energy, the temperature rises and diode gets burned. Due to this reason the simple diodes (where avalanche breakdown occurs) is not used in the applications and instead Zener diode is used in the application circuits of breakdown diodes such as regulating power supply.
so isn't there occured any thermal energy in Zener diode? why? please tell it in details.
@Dr. Somenath • 31 Aug, 2016 Zener has heavily doped configuration, which forms the narrow depletion layer. The covalent bonds break due to the interaction of applied electric field and minority charge carriers, as a result, a small amount of reverse voltage is capable of producing large number of current carriers.
38.6k views

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