A p-n junction has acceptor impurity concentration of `10^(17) cm^(-3)` in the p-side and donor impurity concentration of `10^(16)cm^(-3)` in the n-side. What is the contact potential at the junction? (kT=thermal energy , instrinsic carrier concentration `n_(i)=1.6xx10^(10) cm^(-3)`

Options

A. `(kT)/e log_(e)(4xx10^(12))`
B. `(kT)/e log_(e)(6.3xx10^(22))`
C. `(kT)/e log_(e)(2.56xx10^(20))`
D. `(kT)/e log_(e)(10^(33))`

Answer

A

Explanation

Contact potential `V_(B)=(kT)/e log_(e)((N_(A)N_(D))/n_(i)^(2))`
Here, `N_(D)=10^(16)cm^(-3), N_(A)=10^(17) cm^(-3)`,
`n_(i)=1.6xx10^(10) cm^(-3)`
`:. V_(B)=(kT)/e log_(e)[(10^(17)xx10^(16))/((1.6xx10^(10))^(2))]`
`(kT)/e log_(e)(4xx10^(12))`