Semiconductor and Its Type

Semiconductor is the type of conductor whose conductivity lies between conductor and insulator. On other hand the material having four valance electron is known as semi-conductor. For example :- Gernium and silicon are the example of semiconductor.  The outermost electron or valance electron are four  in both material. There are two type of semiconductor i.e

1)Pure semiconductor

2) Impure semiconductor

1)Pure semiconductor

The Silicon Z=14 is a pure semiconductor. the silicon atom consists of four valance electron surrounding the nucleus and tightly bounded electron. It's central silicon atoms shares it's four valance electron with four adjacent atoms to form covalent bond. In this way the central atom have total eight electrons.

2) Impure semiconductor

When the pure semiconductor is dopped with suitable impurities we obtain a crystal known as impure semiconductor or externsic semiconductor. These are of two type

a)n-type semiconductor

b)p-type semiconductor

a)n-type semiconductor

 The material which have excess of free electron is known as n-type semiconductor. n stands for negatively charged electrons. When the pure silicon crystal is doped with pentravalent electron i.e Arsenic, Phosphorous and Atomuni then four out of five electron in its outermost orbit form the covalent bond with four electron of outermost orbit of silicon atom. The rest of one electron is free in the crystal has shown in figure.

b)p-type semiconductor

The crystal which have excess of hole is known as p-type semiconductor. Here p stands for positive charge. When the silicon is doped with trivalent i.e Aluminium, Boron then only three  electron out of four in outermost electron forms the covalent bond with three electrons in the outermost cell of aluminium. Atom there by leaving one valancy of hole in new electronic configuration such type of crystal is known as p-type semiconductor. In this case the electronic current due to hole such behaves as positive charge. This type of semiconductor is shown in figure.