Vertically coupled quantum dots charged by exciton

By using the fractal dimension method we calculate the ground state wave function of the exciton trapped in a heterostructure consisting of two identical coaxial lens-shaped In(Al)As quantum dots (QDs), deposited on vertically separated wetting layers (WLs), made of the same material, and imbedded inside a matrix of Ga(Al)As in the presence of the external magnetic field. It is shown that the strong confinement in the growth direction provides a considerable tunnelling of the particles in the barrier region in such way that the tunnelling of the electron is more significant that one of the hole due to the difference between their effective masses. In consequence, the central region of two dots with a captured exciton is charged positively whereas the barrier region between them is charged negatively. We found that the charging the barrier region is strengthened under magnetic field applied along the crystal growth direction.