1.

In a pure silicon `(n_(i)=10^(16)//m^(3))` crystal at `300K, 10^(21)` atoms of phosphorus are added per cubic meter. The new hole concentration will beA. `10^19 "per m"^3`B. `10^11 "per m"^3`C. `10^5 "per m"^3`D. `10^21 "per m"^3`

Answer» Correct Answer - B
For intrinsic semiconductor, `n_i=10^16//m^3`and `n_h=n_e` and when phosphorus (pentavalent impurity) is added, it becomes an n-type semiconductor.
`because n_e=10^21//m^3`
`therefore n_h=n_i^2/n_e=(10^16xx10^16)/10^21=10^11//m^3`


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