If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

## Class 12 Physics (India)

### Course: Class 12 Physics (India)>Unit 14

Lesson 4: PN junction biasing

# PN breakdown and avalanche

What happens if the reverse biased voltage gets too high? The diode undergoes breakdown In this video we will explore what this 'breakdown' is. We will see why, usually, it's not advisable to have a large reverse bias voltage across our PN junction diode!  Created by Mahesh Shenoy.

## Want to join the conversation?

• in reverse bias you said that the current is due to minority carriers that is drift current . drift current will not depends on voltage applied it only depends on temperature.but in avalanche breakdown you said when we increase voltage current will increase so breakdown occurs.my question is flow of current in reverse bias is due to minority charge carriers and its independent of voltage then how can current increase in reverse bias if we increase voltage?
• hi Tejaswini !! so the answer to your question is quite simple. In reverse bias, though the curent is due to the minority charge carriers and does not depend on applied potential difference, however on increasing the potential, we are widening the depletion region and hence the electric field. Now the minority charge carriers on P side (electrons) gain enough energy by the virtue of this electric field that it can knock out the electrons from the covalently bonded silicon lattice. This gives rise to a kind of chain reaction which further knocks out more electrons and creates an equal number of holes. hence we see that the number of charge carriers shoots up consequently which contributes to the large current.
• Except the heat generated due to collisions, does crossing the breakdown voltage bring about any other change in the physical property of the material used as a diode?
(1 vote)
• NO,it just heats up and gets malfunctioned.
(1 vote)
• is it possible that the current after the breakdown voltage also occurs because of majority charge carriers breaking loose from the immobile opposite charges in diode. originally my doubt was why in reverse bias majority charge carriers like holes don't accept electrons from electrode considering they are attracted by it, but that is because of the charge of the immobile charges, right??
(1 vote)
• what is the basic purpose of a diode in a circuit?
(1 vote)
• There are many purposes for the diodes like- used as devices called rectifiers which converts AC to DC,also it is used in LED's,in solar panels,as photodiodes which senses light,and many more.
(1 vote)
• Even after breakdown voltage why current was negative