1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Reverse diode

  1. Dec 13, 2014 #1
    I am not getting why there can't be (or very negligible )current in reverse diode.According to this image
    positive terminal of battery would suck electrons from n-type and pass them to negative terminal of battery.And Negative terminal would provide electrons to p type and from there we can see in image force on electrons is opposite to electric field so electrons can easily pass the barrier and can go to n-type and hence complete the circuit(i.e initially electrons were sucked from n-type and lastly they go towards n-type)So in this way in reverse diode also there is sufficient (in good amount)current available.
    Where am i going wrong?

    Attached Files:

  2. jcsd
  3. Dec 13, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor

  4. Dec 13, 2014 #3
  5. Dec 13, 2014 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    I think you need to look at what happens in the depletion zone. Not sure. (It's very late and I'm tired.)
  6. Dec 13, 2014 #5
    I have tried my best to look at all aspects.No ,matter whenever you feel comfortable ,you can answer.Please ..but do explain me this.
  7. Dec 13, 2014 #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    With no voltage applied there is a thin depletion region at the junction. This has very few charge carriers so it acts like an insulator preventing current flow.

    If you inject more electrons into the p-type you reduce the number of holes even more and the depletion region gets wider. You also get a build up of negative charge near the junction that eventually matches the applied voltage preventing further electrons from flowing into the p-type. In this mode the diode behaves a bit like a capacitor.

    Perhaps see..
  8. Dec 13, 2014 #7
    One important thing you must know is we say current to flow in diode iff any charge carriers "cross the junction"between p and n.

    1)ē are majority in N and holes in P.
    2)-ve terminal is connected to P. So it will attract holes from P side . result: holes will move away from junction and get collected in -ve terminal
    3)ē will too move away from junction to the +ve terminal there in N side.
    4)these two will cause widening of depletion region as majority charge carriers move sideways .
    Now ur concept of small current is true . its called reverse leakage current . minority ē in P and minority holes in N will cross junction resulting in current .
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook