Structure of GaN quantum dots grown under “modified Stranski–Krastanow” conditions on AlN

We propose a procedure to grow GaN quantum dots (QDs) on AlN by using the Ga surfactant effect in plasma-assisted molecular beam epitaxy. Self-formed GaN islands were spontaneously generated under vacuum, after evaporation of the Ga bilayer stabilizing the two-dimensional GaN layer grown under Ga-rich conditions. Island characteristics (size and density) are studied as a function of the nominal amount of GaN deposited. We demonstrate that the QD density can be controlled in the ${\text{3×10}}^{10}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}{\text{–2×10}}^{11}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}$ range. It is shown that beyond a given amount of GaN nominally deposited, there is a coexistence between elastic and plastic relaxation, with GaN islands being formed on a partially relaxed two-dimensional GaN layer thicker than two monolayers.