Electron and hole confinement in stacked self-assembled InP dots of different sizes

We report photoluminescence (PL) measurements on doubly-stacked Layers of s elf-assembled InP quantum dots. The amount of material in the lower layer i s kept constant. whilst in the upper layer it is systematically reduced. Ze ro-field PL measurements demonstrate that for each stack only one dot (the largest one) is occupied by an electron, and that when the amount of InP in both layers is the same the upper dots are larger. The behaviour of the ho les, which art: confined by strain in the structure. is revealed by high fi eld (50 T) PL experiments. The holes are found to be increasingly localised to a smaller and smaller volume as the size of the dots in the upper layer is reduced.