I am confused about the meaning of source/drain doping density. Do you mean the value or the unit? There are three ways to specify the doping density, (1) fractional value, that is doping per atom, (2) doping density per cm^2, or (3) directly use density per cm^3. In the first case, the typical value would be 10^(-3), and convert this value to density by dividing it by the volume of an atom. In the second case, the typical value might be 10^(14) /cm^2, and then convert it to density by dividing this value by the grid size.

Sorry sir for late reply. 

It has clarified my doubt. Thanks a lot for your kind response sir.