A semiconductor has equal electron and hole concentration of `6xx10^(8)//m^(3)`. On doping with certain impurity, electron concentration increases to `9xx10^(12)//m^(3)`. (i) Identify the new semiconductor obtained after doping. (ii) Calculate the new hole concentration. (iii) How does the energy gap vary with doping?

Explanation

`n_(i)=6xx10^(8)//m^(3) andn_(e)=9xx10^(12)//m^(3)`
(i) `n_(e) gt n_(1)` so it is N-type semiconductor
(ii) `because n_(i)^(2) =n_(e)n_(h) " "n_(h)=(n_(i)^(2))/(n_(e))=(36xx10^(16))/(9xx10^(12))=4xx10^(4)//m^(3)`