Homogeneous linewidth of the intraband transition at 1.55 μm in GaN/AlN quantum dots

We present homogeneous line width measurements of the intraband transition at 1.55 μm in GaN/AlN quantum dots by means of nonlinear spectral hole-burning experiments. The square-root dependence of the differential transmission signal with the incident pump power reveals the importance of electron-electron scattering in the population relaxation dynamics. We find on the contrary that this scattering process plays a minor role in the coherence relaxation dynamics since the homogeneous linewidth of 15 meV at 5 K does not depend on the incident pump power. This suggests the predominance of other dephasing mechanisms such as spectral diffusion, and temperature-dependent measurements support this hypothesis.