Diode is made by combining different type of semi conducting materials known as p-type semiconductor and n-type semi conductor. We have the pure semi conductor as combinations of silicon atom forming four covalent bonds with other silicon atoms as shown below:
P-type semiconductor:
This type of semiconducting material is made by defusing impurity of trivalent type of material in the pure form of semiconductor as shown below:
In the above example we have used Boron as trivalent impurity and we represent the p-type semiconductor as
In the diagram above circled –ve are fixed ions and small circle are the holes which are the majority charges.
N-type semiconductor:
This type of semiconducting material is made by defusing impurity of pentavalent type of material in the pure form of semiconductor as shown below:
In the above example we have used Antimony as pentavalent impurity. We represent the n-tye semiconductors as
In the diagram above circled +ve are fixed ions and small –ve signs are the electrons which are the majority charges.