How does the doping increase the conductivity of semiconductors?
How does the doping increase the conductivity of semiconductors?
The conductivity of a semiconductor is too low for practical use, The conductivity of a semiconductor can be increased by adding a suitable amount of impurity to perfect crystal. This process is known as doping. It can be done by adding either of two types of impurity to the crystal.
(A) By adding electron rich impurities i.e., group 15 elements to the silicon and germanium of group 14 elements. Out of 4 valence electrons of group 14 elements and 5 valence electrons of group 15 elements, four electrons of each element lead to the formation of four covalent bonds while the one extra electron of group 15 elements become delocalised. Thus, increases the conductivity of the semiconductor. This type of semiconductor is known as n-type.
(B) By adding electron deficient impurity i.e., group 14 to the perfect crystal of group 14 elements when group 13 element is doped to group 14 element it leads to creating a hole in the idea crystal which is known as electron-hole or electron vacancy.
An electron from the neighboring atom come and fill the electron-hole in doing so an electron from the neighbor leaves an electron-hole to its original position. Thus, it increases the conductivity of the semiconductor. This type of semiconductor is known as a p-type semiconductor.
The conductivity of a semiconductor is too low for practical use, The conductivity of a semiconductor can be increased by adding a suitable amount of impurity to perfect crystal. This process is known as doping. It can be done by adding either of two types of impurity to the crystal.
(A) By adding electron rich impurities i.e., group 15 elements to the silicon and germanium of group 14 elements. Out of 4 valence electrons of group 14 elements and 5 valence electrons of group 15 elements, four electrons of each element lead to the formation of four covalent bonds while the one extra electron of group 15 elements become delocalised. Thus, increases the conductivity of the semiconductor. This type of semiconductor is known as n-type.
(B) By adding electron deficient impurity i.e., group 14 to the perfect crystal of group 14 elements when group 13 element is doped to group 14 element it leads to creating a hole in the idea crystal which is known as electron-hole or electron vacancy.
An electron from the neighboring atom come and fill the electron-hole in doing so an electron from the neighbor leaves an electron-hole to its original position. Thus, it increases the conductivity of the semiconductor. This type of semiconductor is known as a p-type semiconductor.
