  We present a theoretical analysis of the phonon-assisted relaxation in a
system composed of two self-assembled vertically stacked quantum dots. We
construct realistic model, which takes into account the geometry and strain
distribution in the system. We calculate phonon-assisted relaxation rates
between the two lowest states (in one- and two-electron cases). The relaxation
rates and energy levels are studied as a function of external (axial) electric
field and geometry of the structure (dot sizes). We show that the relaxation
times can be as low as 1~ps but efficent relaxation occurs only for very finely
tuned dots.
