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Isha Lohan posted an Question
May 23, 2020 • 03:18 am 30 points
  • IIT JAM
  • Physics (PH)

How do increased doping level convert normal diode into zener diode? and then how does increasing doping concentration in zener reduces its breakdown voltage?

Q1. How does increased doping level convert normal diode into Zener diode? Q2.And then how does increasing doping concentration in Zener reduces its breakdown voltage? What particular changes are brought in diode by doping so that it changes normal diode to Zener?

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    Abhishek singh

    For more details. Read this. this will help you a lot. Best regards.

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    Dhairya sharma best-answer

    The diodes designed to work in breakdown region are called Zener diodes.If the reverse voltage exceeds the breakdown voltage, the Zener diode will normally not be destroyed as long as the current does not exceed maximum value and the device closes not over load(While normal p-n junction diodes destroy). Due to the heavy doping, the depletion layer becomes very thin and electric field, across the junction, becomes very high even for a small reverse bias voltage.The use of a sufficiently strong electric field at the junction can cause a direct rupture of the bond. If the electric field exerts a strong force on a bound electron, the electron can be torn from the covalent bond thus causing the number of electron-hole pair combinations to multiply. This mechanism is called high field emission or Zener breakdown. The value of reverse voltage at which this occurs is controlled by the amount of doping of the diode. A heavily doped diode has a low Zener breakdown voltage, while a lightly doped diode has a high Zener breakdown voltage.

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    Somnath best-answer

    Read it carefully, I think you will get your all answer. The width of the depletion region in a p-n junction diode is inversely proportional to the doping concentration of the n and p sides. So, as doping increases, the depletion region width becomes narrower. Electric field is given by E = -dV/dx, that is by the gradient of the barrier potential, for a p-n junction diode. Thus, smaller the width of the depletion region, larger will be the electric field. This high electric field will exert a force on the electrons and holes bounded via covalent bonds, and cause them to move across the junction by breaking the bond. Thus, large number of electron-hole pairs sweep across the junction due to this high electric field, and thereby, breakdown occurs. Such a mechanism of breakdown is popularly known as Zener breakdown, which is distinctly different from avalanche breakdown.

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    Abhishek singh Best Answer

    When you increase doping concentration, then width of depletion region decreases. This width is the characteristic which decide whether zener breakdown will occur or Avalanche breakdown will occur. if the breakdown is due to the increased electric field, it is zener breakdown. Otherwise it is Avalanche breakdown (which occurs in normal pn junction diode).

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