Question

When a diode is heavily doped the
A. Zener voltage will be low
B. Avalanche voltage will be high
C. Depletion region will be thin
D. Leakage current will be low

Answer 1

Hint: The reverse voltage at which all this occurs is basically controlled by the amount of doping done in the diode or how heavily the diode is doped.

Complete step by step solution:
We know that the reverse voltage is totally dependent on the amount of doping done in the diode.
A heavily doped diode has a low zener breakdown voltage whereas a lightly doped diode has a high zener breakdown voltage. Also if the voltage is above approximately 8V, the breakdown phenomena is known as the Avalanche breakdown. Hence upon increasing doping the avalanche voltage will also be high.
Secondly, if the doping in the diode is increased the depletion width decreases or the depletion region becomes thin because free electrons and holes reduce the free ions present. Reduction of positive ions means reduction of depletion region.

The correct answer is (A), (B) and (C)

Additional information: Doping in a process of addition of impurities into an intrinsic semiconductor in order to alter their properties. Normally, there are two types of doping namely trivalent and pentavalent type of doping. For ex. When an intrinsic semiconductor is doped with a trivalent impurity it is known as a P-type semiconductor. Most commonly used impurities are silicon and germanium, when doped contains more number of electrons (n type) and hole (p type).

Note: Zener breakdown and avalanche breakdown are totally opposite to each other. As Avalanche breakdown results in high current flow in the forward bias condition, zener diodes expand the current in the reverse bias.