(a) Find the conductivity of intrinsic silon at `300K`. It is given that `n_(i)` at `300K` in silicon is `1.5x10^(10)//cm`^(3) and the mobilities of electrons and holes in silicion are `1300cm^(2)//V-sec` and `500 cm^(2)//V-sec` respectively.
(b) if donor type impurity is added to the extent of `1` impurity atom in `10^(8)` sillicon atoms, find the conductivity.
(c ) if acceptor inpurity is added to the extent of `1` impurity atom in `10^(8)` silicon atoms,find the conductivuity.
Given: number of `atoms//m^(3)` for `Si=5xx10^(28)`

Explanation

(a) `sigma=n_(i)e(mu_(e)+mu_(h))`
`=1.5xx10^(16)xx1.6xx10^(-19)(1300+500)xx10^(-4)`
`=4.32xx10^(-4)mho//m`
(b) `n_(i)=1.5xx10^(16)//m^(3)`
For silicon, number of `atoms//m^(3)=5xx10^(28)`
`N_(D)=(5xx10^(28))/(10^(8))=5xx10^(20)//m^(3)`
`n_(h)=(n_(i)^(2))/(N_(D))=((1.5xx10^(16))^(2))/(5xx10^(20))=0.45xx10^(12)//m^(3)`
`n_(h)lt ltn_(e)`
`sigma=n_(e)emu_(e)=5xx10^(20)xx1.6xx10^(-19)xx1300xx10^(-4)`
`=10.4mho//m`
(c ) `N_(A)=5xx10^(20//m^(3)`
`n_(e)=(n_(i)^(2))=((1.5xx10^(16))^(2))/(5xx10^(20))=0.45xx10^(12)//m^(3)`
`n_(h)gt gtn_(e)`
`sigma=n_(h)emu_(h)=5xx10^(20)xx1.6xx10^(-19)xx500xx10^(-4)`
`=4 mho//m`