With the development of several experimental techniques

for example

molecular beam epitaxy

metal-organic chemical-vapour deposition and electron beam lithography combined with reverse mesa etching

there has been a lot of work devoted to the understanding of hydrogenic-impurity states in low-dimensional semiconductor heterostructures such as quantum wells

quantum wires and quantum dots.In recent years

there has been great interest in investigating quantum dots both theoretically and experimentally.Due to the small structures of QD's

some physical properties such as optical and electron transport characteristic are quite different from those of the bulk materials.The study of the impurity states in these low dimensional structures is an important aspect to which many theoretical and experimental works based.Recent investigations in the reduced dimensionality show the impurity within the reduced dimensionality shows that the impurity binding energy will be enhanced with the deduction of the dimensionality.