HOW DIODES ARE MADE AND HOW THEY WORK {THE THEORY & CHEMISTRY IN IT}.

In this forum you will learn about the basics of semi conductors and how diodes are made and work.

I. Semi-conductorsare elements or materials that lie between insulators and conductors. They partially conduct current. They include (silicon{Si} , Germanium{Ge} ).

Group 4 elements have poor conductivity of current in their original structure and hence these elements are referred to as intrinsic semi conductors.

Semi conductors are classified into two categories,

· Intrinsic semi conductors.

· Extrinsic Semi conductors……refers to an extrinsic semi conductor to which foreign material has been added. In this topic, they come from group 3&5 elements. They are still classified into two groups.

N-Type Extrinsic semi conductor.
P Type extrinsic semi conductor

A diode is made up from semi conductor material from group 3of the periodic table, either mixed with a group 4 or 5 element. The group 3 elements ,ie. Silicon & Germanium.

N-Type extrinsic semi conductors..

N stands for negative.

P – Positive.

When a group 3 element is added a group 4 element atom at a ratio of 1:10 like phosphorous the resulting semi conductor is referred

to as a {N-Type} because it has negative particles.

Each atom of silicon will combine to form a covalent bond with surrounding electrons. I.e. there will be sharing of electrons. There will be an electron of phosphorous which did not get its partner to form covalent bond with. This electron is free to move about in the material, for every atom of phosphorus there is a free electron. The more we add phosphorus atoms the more we get free electrons thus raising the conductivity of the extrinsic semi conductor. Phosphorus is referred to as the donor atom because it donates an electron. This is taken to be negative (-) negative

P-type extrinsic semi conductor.

This is formed combining or doping a group 4 element with a group 3 element ie. { Si-Al}. each atom of silicon requires 4 electrons to be stable but Al can only provide 3 electrons to the intrinsic semi conductor.This means there is a lack of electron to form a covalent bond between Si and Al. that absence is referred to as {Hole}. The hole is capable of attracting electrons from covalent bonds of other atoms.

When that happens a hole will be created and thus a Hole can move randomly in a material, the hole is taken to be (positive) charge and denoted by a {+}.

P-N JUNCTION DIODE

The pn-junction is formed by combining the P type and N type semi conductors.

The two pieces are brought together and meet at a junction. All the holes and electrons recombines leaving a region that does not have charges. The region is known as depletion layer.