Low temperature non radiative process's effects on the optical emission of GaN/Al0.5Ga0.5N nanostructures

The optical properties of self-assembled (0001) polar and (11-22) semipolar GaN nanostructures embedded in Al0.5Ga0.5N matrix and grown by molecular beam epitaxy are reported. A statistical analysis of the nanostructure's height dispersion is done by transmission electron microscopy (TEM) in order to have a good estimation of the electric field inside the structure and also to be able to give an explanation for the saturation of the emission energy for polar orientation when the height exceed some values. It is found that the non-radiative processes are not negligible at low temperature and should be taken into account as the radiative ones. The combined comparison between experimental results and our model has allowed us to determine the non-radiative lifetimes at low temperature. We show that the use of epitaxial lateral overgrowth, in addition to the growth of GaN nanostructures, will improve the radiative efficiency that can reach 60%.