Résumé
Properties of self-assembled quantum dots (QDs), often referred to as artificial atoms in solid state, are very interesting in order to study physical effects specific to single quantum systems such as the single-photon emission. Thanks to their huge vertical quantum confinement, GaN QDs are emitting even at room temperature and on a large UV range. This peculiarity makes GaN QDs good candidates for fundamental physics as well as conception of devices such as UV-LEDs. In so-called thick QDs (height larger than 2.3 nm), the energies of the confined electronic states are determined by the quantum confined Stark effect. On the contrary, in thin QDs (height smaller than 2.3 nm) the quantum confinement plays the major role, thus leading to a significantly smaller homogeneous linewidth and to the resolution of the exciton fine-structure splitting [Kindel, PRB81, 241309]. As far as time-resolved measurements are concerned, several papers reported experiments in thick QDs emitting at 350nm or more, either in polar [Bretagnon, PRB73, 113304] or non-polar nanostructures [Founta, APL86, 171901]. We report photoluminescence decay time measurements in thin GaN QDs emitting between 280nm and 360nm. For QDs emitting at 290nm we observe a monoexponential decay and the abscence of any red shift for the luminescence spectrum shows that we are in the regime of a single electronhole pair per dot. In this case, we measure the intrinsic radiative recombination time, without any perturbation due to the Stark effect. We find a radiative lifetime of about 350 ps in good agreement with our theoritical model.