What amount of inpurity of atomic density in added toform N-type semiconductor in Ge semiconductor of conductivity `sigma` is `5Omega^(-1)cm^(-1)` Mobility of electron in N-type semiconductor is 3900 `cm^(2)V^(-1)s^(-1)`. Ignore conductivity due to hole. `(e=1.6xx10^(-19)C)`

Options

A. `2.25xx10^(21)m^(-3)`
B. `4.007xx10^(21)m^(-3)`
C. `8013xx10^(21)m^(-3)`
D. `8.013xx10^(21)m^(-3)`

Answer

D

Explanation

`8.013xx10^(21)m^(-3)`
`sigma=5Omega^(-1)cm^(-1)=500Omega^(-1)m^(-1)`
`mu_(e )=3900cm^(2)V^(-1)s^(-1)=0.39m^(2)V^(-1)s^(-1)`
Now `sigma=en_(e )mu_( e)`
`therefore n_(e )=(sigma)/(emu_(e ))`
`therefore n_(e )=(500)/(1.6xx10^(-19)xx0.39)`
`therefore n_(e )~~8.013xx10^(21)m^(-3)`