A semiconductor has equal electron and hole concentration $6 \times 10^8\;m^{-3}$. On doping with a certain impurity , electrons concentration increases to $8 \times 10^{12}m^{-3}$. Identify the type of semiconductor after doping

Question

$\begin{array}{1 1} n- type \\ p-type \\ p-n \;type \\ n-p-n type \end{array} $