What is a diod?

 What is a diode?

             

            Before we start first of all we have understand the history after which diodes are made.
In the beginning there were vacuum tube made for the electronics models and amplification of signal. they produce much heat so that there was also a cooling system required. They also occupy more space while there efficiency was not too good.
           After that when semi conductors were discovered a new revolution became in the field of electronics and solid state devices are made up using the semi conductor materials.
           Before talking about the diode we study the material and there properties of which they were made. There construction is based on semi conductor materials. In pure crystalline form at room temperature there properties lie between conductors and insulators. There are four electrons in there valance shell due to which they are not a good conductor nor insulators. To make them useful they are doped with the group 3 and 4 elements.

           The process of mixing a semi conductor with any other trivalent or Pentavalent impurity to make them useful is known as the doping process.
There are two terms used for the semiconductor materials which are intrinsic and extrinsic.
The semi conductors in pure form without any mixed impurity are called INTRINSIC semiconductors.
While the material made after mixing impurities in pure semi conductors are called extrinsic semi conductors. After doping there are two types of materials formed which are N-type and P-type semiconductors. To make a N-type semi conductor elements of group 4 are mixed with pure semiconductors which are Pentavalent material. Following are some examples of Pentavalent material.
Phosphorus (P).
Arsenic (As).
Antimony (Sb).
Bismuth (Bi) .
 To make P-type materials the pure semi conductors are doped with the elements of group3 which are trivalent impurities. Following are some examples of trivalent impurities.
Aluminum (Al)
Gallium (Ga)
Boron (B)
Indium (In).

How DIODES ARE MADE?

                

                  Diodes are made by using semiconductor materials with diffusion process.

when a P-type material if  joined to a N-type material using diffusion technique a P-N junction is formed there.

The area where two intrinsic material meets is called a junction and in case of P-type and N-type it is called a P-N junction. Mostly there is silicon is used to make a diodes while Germanium is also used but not at large scale. When a P-N junction is made there a is a potential barrier build up across the junction which is called  barrier potential. This barrier potential requires some voltages to over come and to switch on the diode. In case of silicon it is 0.7 volts for ideal diode and for germanium it is 0.3 volts.

                   When P-N junction is made there are some holes and electrons starts diffusing into each other and creates +ve and -ve ions across the junction. The area where these ions are present is known as the depletion layer or space charge.

This semiconductor diode is also known as the P-N junction diode or simply diode.

DIODE?

      A diode is a unidirectional semiconductor device which have two terminals and one junction.
it is used as a switch and rectifier.