Suppose a pure Si-crystal has `5xx10^(28) "atoms" m^(-3)`. It is doped – InterviewSolution

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1.	Suppose a pure Si-crystal has `5xx10^(28) "atoms" m^(-3)`. It is doped by 1 ppm concentration of pentavalent As. Calculate the number of electrons and holes. Give that `n_(i)=1.5xx10^(16)m^(-3)`.
Answer» `1"ppm"=1` part per million `=1/10^(6)`. so no. of pentavalent As atoms doped in given Si crystal, `=(5xx10^(28))/10^(6)=5xx10^(22)m^(-3)`. As one pentavalent atoms donates one free electron to the crystal structure, so no. of free electrons in the given si crystal, `n_(e)=5xx10^(22)m^(-3)` Number of holes, `n_(h)=n_(i)^(2)/n_(e)=(1.5xx10^(16))^(2)/(5xx10^(22))` `4.5xx10^(9)m^(-3)`

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