To boost a semiconductor’s conductivity, impurity atoms are added to a pure or intrinsic semiconductor through the process called “doping.” There are two methods of doping: adding an n-type dopant or adding a pentavalent dopant to an intrinsic semiconductor to create an n-type semiconductor.
Doping: n- and p-semiconductors
An n-type semiconductor is created when group V elements like phosphorus and arsenic are doped in group IV elements (Si or Ge). The extra negative charges caused by the impurity’s extra electrons are what cause the electrical conduction.
A p-type semiconductor is created when group III elements like boron and gallium are doped with group IV elements (Si or Ge). The extra positive charges caused by the impurity’s electron holes are what cause the electrical conduction.
Conditions Required for the Doping Process
- The atom that needs to be doped in the crystal must be positioned exactly where the semiconductor atom is.
- After the dopants have been inserted, the crystal shouldn’t have any distortion.
- The size of the dopants should exactly match the size of the crystal’s atoms.
- The amount of doping in a crystal shouldn’t be greater than 1%.
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