Silicon and germanium exhibit this behavior and are called intrinsic semiconductors.
The conductivity of these intrinsic semiconductors is too low to be practically used.
Doping
o
The conductivity of metal is increased by adding an appropriate amount of suitable impurity.
o This process is known as doping.
o
It can be performed with an impurity which is electron rich or electron deficient than the intrinsic semiconductor silicon or germanium.
Fig. Doping electron rich impurity into an intrinsic conductor o Such impurities introduce electronic defects in them.
1. If NaCl is doped with 10-3mol % of SrCl2, what is the concentration of cation vacancies?
2. 1 Cation of Sr 2 + = 1 cation vacancy in NaCl.