An intrinsic semiconductor has `5 xx 10^(28)` atoms and the carrier concentration `1.5 xx 10^(16)` .If it is doped by a pentavaIent impurity in the ratio `1:10^(6)` , then caIcuIate number density of hoIes as charge carriers.

Explanation

On doping by pentavalent impurity n-type semiconductor is formed. Here we neglect the number density of the thermal electrons in respect to the number density of electrons as majority carriers. Hence the number density of electrons in n -type semiconductor,
n=`(5xx10^(28))/(10^(6))=5xx10^(22) "m"^(-3)`
Given `n_(i)=1.5 xx 10^(16) "m" ^(-3)`
So the number density of holes ,
P=`(n_(i)^(2))/(n)=(1.5xx10^(16))^(2)/(5xx10^(22))=4.5 xx10^(9)"m"^(-3)`