This work will demonstrate that impurities within semiconductor crystals can be thought of as the ultimate in quantum dots, with the three-dimensional confining potential being provided by individual atoms which are each capable of localising single electrons or holes. A heterostructure confining potential provides a means to tune the energy levels of the impurities. Just as importantly, quantum well systems with these embedded quantum dots can be fabricated to very high qualities with contemporary molecular beam epitaxy growth techniques. In this work the first steps to utilizing internal transitions of these single atom quantum dots to develop Terahertz lasers are reported. These include time resolved measurements of the excited impurity state lifetimes performed at the Dutch free-electron laser.