Question

How are zener diodes made?

Answer 1

PN junction diode:

1. A diode is a semiconducting device, that allows current to flow in one direction but not the other.
2. A semiconductor is a kind of material, in this case, silicon or germanium, whose electrical properties lie between those of conductors (metals) and insulators (glass, rubber).
3. You can change the behavior of pure material, like silicon, and turn it into a semiconductor by doping.
4. With N-type doping, phosphorus or arsenic is added, in parts per billion, to the silicon in small quantities. It takes only a very small quantity of the impurity to create enough free electrons to allow an electric current to flow through the silicon. Electrons have a negative charge, hence the name N-type.
5. In P-type doping, boron or gallium is added to the pure silicon. Those elements each have three outer electrons. The absence of an electron creates the effect of a positive charge, hence the name P-type. Holes can conduct current. A hole happily accepts an electron from a neighbor, moving the hole over a space.
6. Diodes are made from two differently doped layers of semiconductor material that form a PN junction.
7. The P-type material has a surplus of positive charge carriers (holes) and the N-type, a surplus of electrons.

Zener Diode:

1. Zener diodes are made by heavily doped n-type and p-type semiconductors.
2. The quantity of the doping of the semiconductors is kept different so that their breakdown voltage is different.
3. A Zener Diode, also known as a breakdown diode, is a heavily doped semiconductor device that is designed to operate in the reverse direction.
4. When the voltage across the terminals of a Zener diode is reversed and the potential reaches the Zener Voltage (knee voltage), the junction breaks down and the current flows in the reverse direction. This effect is known as the Zener Effect.
5. A Zener diode operates just like a normal diode when it is forward-biased. However, a small leakage current flows through the diode when connected in reverse biased mode. As the reverse voltage increases to the predetermined breakdown voltage, the current starts flowing through the diode. The current increases to a maximum, which is determined by the series resistor, after which it stabilizes and remains constant over a wide range of applied voltage.