Modified Stranski-Krastanov growth in stacked layers of self-assembled cubic GaN/AlN quantum dots

In a stacked structure of cubic GaN/AlN islands grown in a Stranski-Krastanov mode, the critical thickness for the GaN islanding (2D–3D transition) decreases by a factor of up to 10 between the initial dot layer and the third one. This variation of the critical thickness is strongly dependent on the AlN spacer thickness. Moreover, we observe systematically a change of the quantum dot strain state and an increase of island size, depending on the GaN island layer number.