Conducitvity of a semiconductor is too low for practical use the conductvity of a semiconductor can be increased by adding a suitable amount of impurity to perfect cyrstal 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 doping increase rich impurities i.e group 15 elements to the silicon and germainum of group 14 elements Out of 4 valance elements of group 14 elements and valance electrons of group 15 elements four electrons of each element lad tobecome delocallised.
thus increase conductvity of semiconductor this type of semiconductor isknown as n- type semiconductor .
B . by adding electron deficient impurity i.e group 14 to the pe3rfect crystal of group 14 element whrn group 13 element is doped to group 14 element it lead to crate hole in the ideal crystal which as electron hole or electron veacancy .
An electron from the neighbouring atom come and fill the electron hole in doing so an electron form the neighbour leaves an electron hole to its original position thus it increase conductivity of semiconductor this type of semiconductor is known as p-ytpe semiconductor .
