question_answer

A pure germanium semiconductor is doped with donor atoms of density \[8\times {{30}^{x}}c{{m}^{-3}}\]in order to obtain an n-type semiconductor whose conductivity is \[5mho\,c{{m}^{-1}}\], The value of x is____.                            (The mobility of electrons in n-type germanium is \[3900\,\text{c}{{\text{m}}^{2}}\,{{\text{V}}^{-1}}\,{{\text{s}}^{-1}}\]and density of holes is negligible.)

Answer:

15