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)=6 times 10^(8)//m^(3) " and " n_(e)=9 times 10^(12)//m^(3)`
(i) `n_(e) gt n_(i)` so it is N-type semiconductor
(ii) `because n_(i)^(2)=n_(e)n_(h) rArr n_(h)`
`=n_(i)^(2)/n_(e)=(36 times 10^(16))/(9 times 10^(12))=4 times 10^(4)//m^(3)`