Doping Of Semiconductors

Description:

Due to the drawbacks of intrinsic semiconductors they cannot be used in devices. To make intrinsic semiconductor useful doping of semiconductor is done.

DOPING

Doping is mixing semiconductor with a CHOICED impurity in a MEASURED quantity. In other words, the process of adding impurity to pure semiconductor is called doping.

The product formed after doping is called doped semiconductors or extrinsic semiconductors.

Doping is represented in parts per million (ppm) i.e. if we use 3ppm in doping of silicon with aluminium this means 3 atoms of aluminium are added in 1 million atoms of silicon.

Doping is done using neighbouring elements only so that it does not affect the crystal structure of semiconductor.

Doping can be classified in two types:

• P type − When silicon or germanium crystal is doped with trivalent impurity it is called as P type doping.

  e.g.: aluminium

• N type − When silicon or germanium crystal is doped with pentavalent impurity it is called as N type doping.

  e.g.: phosphorous