In recent years, progress in nanotechnology has allowed manufacturing of ultra small systems in the areas of electronics and opto-electronics with a high-precision capability of controlling the size and shape. Quantum dots (QD) are typical examples of nanosystems where the electrons are confined in all the 3-dimensions. These quasi-zero-dimensional systems show exotic electronic behaviors typical of the atom like discrete density of states (DOS) of the carriers. QDs could incorporate dopant impurities as a crucial ingredient for their proper functioning. The great interest for understanding...