The concertration of hole-electron pairs in pire silicon at `T=300K` is `7xx10^(15` per cubic metre. Antimoy is doped into silicon in a proportion of `1` arom in `10^(7)` atoms. Assuming that half of the inpurity atoms contribute electrons in the conduction band, calculate the factor electrons in the conduction band, calculate the factor by which the number of charge carriers increase due to doping. the number of silicon atoms per cubic meter is `5xx10^(28)`.

Explanation

`n_(i)7xx10^(15)//m^(3)`
`N_(D)=(5xx10^(28))/(10^(7))=5xx10^(21)//m^(3)`
Half of impurity atoms contribute electrons.
Before doping, number of charge carries `=2xx7xx10^(15)`
`=14xx10^(15)//m^(3)`
After doping, number of charge carries
`=(N_(D))/(2)+14xx10^(15)`
`=2.5xx10^(21)+14xx10^(15)=2.5xx10^(21)`
the factor by which the number of charge carries is increased
`=(2.5xx10^(21))/(14xx10^(15))=1.8xx10^(5)`