Probing exciton localization in nonpolarGaN∕AlNquantum dots by single-dot optical spectroscopy

We present an optical spectroscopy study of nonpolar $\mathrm{Ga}\mathrm{N}∕\mathrm{Al}\mathrm{N}$ quantum dots by time-resolved photoluminescence and by microphotoluminescence. Isolated quantum dots exhibit sharp emission lines, with linewidths in the $0.5–2\mathrm{meV}$ range due to spectral diffusion. Such linewidths are narrow enough to probe the inelastic coupling of acoustic phonons to confined carriers as a function of temperature. This study indicates that the carriers are laterally localized on a scale that is much smaller than the quantum dot size. This conclusion is further confirmed by the analysis of the decay time of the luminescence.