Optical properties of GaN quantum dots grown on nonpolar (11-20) SiC by molecular-beam epitaxy

We report on nonpolar GaN quantum dots embedded in AlN, grown on (11-20) 6H–SiC by plasma-assisted molecular-beam epitaxy. These dots are aligned in the growth plane and present a constant aspect ratio of 10. Their optical properties were studied as a function of GaN coverage. Especially, the variation of their emission energy as compared to that of (0001) GaN quantum dots is a clear fingerprint of the reduced internal electric field present in these nonpolar nanostructures. Time-resolved spectroscopy confirmed this result by revealing lifetimes in the few 100 ps range in contrast to the much longer ones obtained for the (0001) GaN quantum dots.