Doping is the process of adding impurities to intrinsic semiconductors in controlled manner to improve its conductivity. Normally Trivalent and Pentavalent elements are used to dope Silicon and Germanium.
When an intrinsic (pure) semiconductor is doped with Trivalent impurity it becomes a p-type semiconductor. The p stands for Positive, which means the semiconductor is rich in holes or Positive charged ions.
When we dope intrinsic (pure) material with Pentavalent impurities we get N-Type semiconductor, where N stands for Negative. N-type semiconductors have Negative charged ions or in other words have excess electrons in it.
Doping is done in semiconductors for 3 main reasons:
1) To change the conductivity (resistivity) of the material.
2) To create “traps” in the material that speed up recombination of electrons and holes.
3) To produce junctions.
An important condition to doping is that the amount of impurity added should not change the lattice structure of the Semiconductor. To achieve this the size of the dopant and Semiconductor atoms should be the same.
To learn more about doping continue to watch this video lecture series.
